The RavTrack system architecture compared to common “cellular” GSM/GPRS tracking systems.

Most GPS tracking systems use “cellular” GSM/GPRS based transponders.  Once the device calculates position from the GPS satellites the transponder transmits the position to the cellular GSM/GPRS network of receivers in the area.  At this point the GSM/GPRS system owner/operator transports the data to your HQ tracking location.  Obviously they charge a fee for this service, and are in control of your data as well.

RavTrack is different in that the RavTrack transponders transmit position over a mobile radio frequency, typically designated by a government administrative agency for your exclusive use.  A GSM/GPRS system is not used; instead the operator of the RavTrack system installs one or more RavTrack receivers in position(s) around the area to be tracked.  One receiver is capable of covering an area commonly of 10-25 mile radius from its own position, although this range varies a good deal depending upon how high in elevation the receiving antenna is, and what the local terrain is like.

As the RavTrack operator owns both the GPS position transmitters as well as the receiver(s), the fleet may transmit positions very frequently without concern for any fees, and with extremely fast delivery of data.

Many users of RavTrack install just one receiver, and mount it high atop a building, antenna tower, or point of elevation to cover the tracking area.  This area is often a city, an open pit mine or other remote area, or a fleet of boats where the group can be tracked by other boats in the fleet.  Since the entire system operates independently from any GSM/GPRS network, RavTrack can work anywhere GPS satellite lock can be acquired.  In fact, the entire system can be mobile and any fleet member can receive GPS reports from other fleet members in radio range, even while all are traveling at high speeds.

If a larger area of coverage is needed, or the tracking HQ is not at a good location for area reception, a single RavTrack repeater may be established at a preferred location where the repeater then wirelessly relays the transmissions it receives to the tracking HQ.  If the area of coverage is very large, then multiple receivers may be installed and connected together as well as to the tracking HQ via an IP backbone, which can include either a private network or the public internet.  The determination of the proper receiver layout is based principally upon the area the system must cover for effective fleet tracking, as well as the local terrain.

There is little doubt that the RavTrack system offers significant performance advantages and other benefits over GSM/GPRS based systems.   Primarily the decision to install RavTrack versus an alternative system comes down to the area of tracking coverage required and the size of the fleet involved.  RavTrack can handle very large fleets.  However, when the area of coverage required is vast, requiring a large number of receivers, and the fleet itself is small, the cost per vehicle may become prohibitive.  In these cases the operator must rely on a pre-installed network of GSM/GPRS system receivers owned and operated by another entity and pay their monthly fees.  If GSM/GPRS service coverage is poor then an expensive communications satellite relay may be a considered alternative.

For a point-by-point comparison of RavTrack versus GSM/GPRS “cellular” vehicle tracking systems please refer to this tech blog article: http://ravtrack.com/GPStracking/553/553/

Overview

The M7 GX series of GPS transponders are excellent for real-time tracking of vehicles.  They work in remote areas and have a very fast update rate.  By installing a Raveon GPS transponder in an off-road race vehicle (buggy, truck, motorcycle, UTV, or quad) race teams and support personnel have an exciting new way of watching the race and the race-vehicle can quickly locate its support personnel.

The system operates as follows:

1. The M7 radios in the system must be programmed to a valid VHF or UHF radio frequency.  Raveon has both VHF and UHF versions of its M7 GPS transponder.
2. Each vehicle is assigned a unique ID number (1-9999).  The ID number is programmed into the M7 radio.
3. The TDMA time and the time-slots for each M7 radio must be configured.  The TDMATIME is how often the radio transmits its position.  The SLOTNUM is the unique slot number each radio will transmit in.  Slot numbers start with 1 and are sequentially numbered.
4. The M7 GX GPS transponders are installed in race and support vehicles. They will periodically transmit its GPS position out using its built-in VHF or UHF 5 watts radio.
5. Besides transmitting GPS position, the M7 GX can also receive the GPS position from other vehicles.  As long as the GPS transponder is within radio range of another vehicle, it will output a message via its RS232 serial port whenever it hears the GPS position of another vehicle.
6. The M7 GX GPS transponder has an internal GPS receiver and a VHF or UHF radio transceiver.  Out of its RS232 serial port, the M7 will periodically output the local GPS location using standard NMEA messages (GGA, GLL, RMC…)
7. Optionally, in any vehicle, the M7 GX GPS transponder may be wired to a GPS display in the vehicle.  When connected to a suitable display, the M7 will send a message to the display telling it to put an icon at the location of any vehicle it receives that report its GPS position.
8. If you want to track using a PC, simply load RavTrack PC into a laptop, desktop, or notebook, and connect it to another M7 G GPS transponder.  Raveon sells RavTrack PC for dispatch and AVL applications, but it makes a nice in-vehicle display or data logger for post-race replay of an event.

Things to consider

1. The M7 GX uses licensed UHF and VHF radio channels.  Unless you are operating on a VHF MURS radio channel, you will need to obtain an FCC license to use this product.
2. The GPS tracking range is limited to the radio range of the 5-watt radio transceiver built into the M7.

The M7 GX series of GPS transponders may be directly connected to a Lowrance Globalmap 480, 540C, 7200 or a Globalmap 840C navigation display.  Various Garmin hand-held GPS receivers also work with the M7.  Most GPS receivers that support RS232 serial NMEA message input will work with the M7, but some will not.  Contact Raveon for details on which models work, or try it out and see.

When connected to da GPS display, the display map will show the location of the vehicle it is in PLUS the location of all other M7 transponders within radio range.  This unique feature allows a person to quickly, easily, and inexpensively, make a mobile AVL system for tracking cars, trucks, racecars, or construction equipment.

The GPS display must have an interfaces for a “NMEA 0183? devices, which is another way of saying that they can connect to other devices using a serial cable.   The NMEA 0183 is an RS232 serial connection that typically operates at 4800 baud.  It is used to exchange waypoint and other information between displays, GPS devices, and transponders.

When Raveon’s M7 GX transponder is connected to a GPS display using the NMEA 0183 connection, the M7 transponder can put icons on the screen of the display.  As the transponder received updated positions from other vehicles, it updates the position of the icons on the Lowrance display. It does this by sending a “GPWPL” message to the display.  The display interprets the message as a waypoint location, and puts a waypoint at the specified location on the map, with the ID number of the vehicle that is at that location.

This type of Automatic Vehicle Location (AVL) technology must be installed and maintained by qualified service personnel.  If you or your team do not have the technical skills required, contract with a two-way radio service shop or similar type company to install and maintain your system.

The M7 GX GPS Transponder

The M7 GX GPS transponder is available in two forms; the Standard and the Weatherproof versions.

Standard M7 GX                                         Weatherproof M7 GX WX

If the unit will be in a location where it will get wet or washed, the weatherproof version should be used.

The technical documentation for Raveon’s GPS tracking products is located at: http://ravtrack.com/Downloads.html

The Technical Manual for the GPS transponder is located here: http://ravtrack.com/pdf_manuals/RV-M7-GX_Tech_Manual.pdf

Raveon highly suggest you familiarize yourself with the product, read the manuals, as well as read and heed all safety warnings before proceeding.

Plan Your System

Because the M7 usually must be removed from the vehicle to reprogram it, it is important that you plan your system correctly and configure the M7s as planned.  To facilitate this, Raveon has a Windows program called RadioManager that gives the user a graphical interface to program the radio.  Or, you can use any terminal program such as HyperTermina.
A free download of RadioManager is available here: http://ravtrack.com/Radio-Manager-Download.html

You must configure a number of paramters and the system frequency.  Your GPS position transmission rate, radio IDs, and a number of other settings must be pre-configured for your system to operate properly. Read the Technical Manual for information on how to configure your system and program your M7 radios.

Record your system configuration in a table or spreadsheet like the one on the following page.

Raveon M7 GX  GPS Transponder System Configuration Worksheet

Setup and Initial Configuration

Before the M7 is installed in the vehicle, it must first be programmed.  From the factory, they are configured to work, so all you will need to do is configure them for your operation.

You must read the M7 GX Technical Manual to properly configure the M7.

Here is a summary of the steps you must perform.

1. Connect a DC power source to the DC IN connection on the front of the modem.
2. Connect a computer terminal, or PC computer running HyperTerminal, to the 9-pin I/O connector.  The factory default serial ports settings are 4800 bps, 8 data bits, 1 stop, no parity. Note, the serial port may be 38400bps if the RV-M7 GX is in GPS modes 2 or 3.
3. Put the RV-M7 GX into the command mode.  (enter +++ per Section Error! Reference source not found.)
4. Program the modem’s operating frequency to your desired operating frequency.  This is done with the ATFX xxx.xxxxx command. See the Section Error! Reference source not found. for information describing the various parameters that may be modified in the modem.  In most applications, the default settings from the factory will work fine.
   Note: The MURS version of the M7 (RV-M7-VM), the unit is pre-set to the 5 MURS channels on channels 1-5.  The user cannot change the frequency of the M7, only the channel number.   Use ATHP x to select the MURS radio chanel.
5. With the unit in the command mode, change any of the default operating parameters that must be modified.  From the factory, the modems are configured and delivered ready-to-use.  Out of the box, they will communicate on the default radio channel using the factory defaults.  Raveon highly recommends you test them first with the factory defaults and see how they work before reprogramming them. In general, the parameters you may want to modify will be:

ATFX Frequency for this channel. Set to your frequency.

GPS x Set the operating mode of this unit. See Section Error! Reference source not found. for a list of the various modes.

ATMY The individual ID of this unit.  Default is 0001.  Number all of your RV-M7 GX transponders with a different MYID.  Raveon recommends sequentially numbering them, starting at number 1.

ATDT The address of the unit this modem will talk to.  Default is 0001.

ATMK The network address mask. Default is F000.  This means this unit will receive all transmissions from any other unit with an ID beginning with 0 (0001 thru 0999).

KEYPHRASE Enter a security key code.  Use any word or phrase 1-16 characters long.  It is case-sensitive.  DO NOT FORGET WHAT YOU SET IT TO!  The KEYPHRASE is the only parameter that cannot be read out of the RV-M7 GX.   It must be the same as the KEYPHRASE programmed into all the other RV-M7 GX transponders in your system.  The factory default KEYPHRASE is RAVEON, call capitals.

SLOTNUM This will change the TDMA slot assignment, leaving the ID (MYID) unchanged.  Typically, the ID and the slot number are the same.  Once this command is used, the TDMA slot number for this transceiver to will not change if the ID of the device is changed.   Set SLOTNUM to -1 to force the Slot Number to be automatically set to the MYID of the radio. This is the factory default setting.

The radio is now ready to install and use.  Remember, that from the factory, all RV-M7 GX modems are configured to simply work.  Plug in power and connect to the serial port at 4800 baud, and the modems will communicate on the default channel.

What you will see come out of the serial port with the factory default settings (GPS 4 mode), is a $GPWPL… message, every time one RV-M7 GX in your system transmits.

The RV-M7-VM  MURS version of the M7 has five user selectable channels.  The channel is selected with the ATHP command.  The RV-M7-VM modem is factory-set to these five channels, and the modem cannot be programmed to operate on any frequency other than these five.

1              151.820 MHz
2              151.880 MHz
3              151.940 MHz
4              154.570 MHz
5              154.600 MHz

M7 GX Installation in the Vehicle

You will need to connect at least 3 things to the M7 GPS transponder and maybe a fourth.  They are:

1. DC Power  (10-16V DC)
2. Radio antenna.  UHF or VHF depending upon the band you use.
3. GPS antenna.
4. Optional display. (Lowrance, PC, Garmin…)

To install a GPS transponder in a vehicle, follow these steps:

1. Secure the RV-M7 modem using the mounting holes on the side flanges of the unit.  You might want to locate it so that the front panel LEDs are visible.
2. Connect a DC power source to the DC IN connection on the front of the modem.  Use the supplied cable, or 18AWG wire, and connect the RED wire to +, and the black wire to – (ground).   The black wire and the case of the RV-M7 should be connected to earth ground.
3. Connect a good quality antenna, tuned to the operating frequency, to the RF connector on the front of the modem.  Use a good antenna, and mount it  is at as high-above obstructions as possible.  On the roof is the best.
   

   

   Avoid using magnet-mount antennas for race vehicles.  They may be OK for a chase vehicle if the driving and terrain is not too rough.

4. Connect a GPS antenna to the SMA connector of the RV-M7 GX.  Although a passive antenna may work if the cable length is very short, it is recommended that an amplified antenna be used, rated at 3.3V operation. Mount the GPS antenna so it can see the sky. On the roof of the vehicle is best. You may have to experiment with locations to find one that is easy to mount the antenna to and can also see the sky.  There are two popular mounting methods: thru-hole and magnet-mount. If you use a magnet-mount GPS antenna, we recommend you also zip-tie it to the vehicle.
5. Wire the GPS display or computer, terminal, controller, or other hardware device that will be using the RV-M7 to its DB-9 serial I/O connector using a shielded cable. Secure it to the RV-M7 with the two mounting screws on the sides of the DB-9 connector.   For a tracking-only application, nothing needs to be wired to the DB9 connector of the M7. Only if you have an in-vehicle display do you connect to the DB9.  The following section describes how to wire in a Lowrance to the M7, but most other displays will be similar.  More GPS display information is on Raveon’s web site here:  http://ravtrack.com/GPStracking/category/installation/

Lowrance 480, 540C, 7200 and 840C Wiring

From the Lowrance technical manual, here is how their NMEA 0183 interface works:

NMEA 0183 Cable Connections

NMEA 0183 is a standard communications format for marine electronic equipment. For example, an autopilot can connect to the NMEA interface on the GlobalMap 540c and receive positioning information.  The GlobalMap 540c can exchange information with any device that transmits or receives NMEA 0183 data. See the following diagram for general wiring connections. Read your other product’s owner’s manual for more wiring information.

Below is the cable diagram from the Lowrance user manual for the data cable.  Often, installers will cut-off the data cable wires, making the connection to the cable a challenge.

NMEA 0183 Wiring (Data cable)

To exchange NMEA 0183 data, the GlobalMap 540c has one NMEA 0183 version 2.0 communication ports. Com port one (Com-1) can be used to receive NMEA format GPS data. The com port can also transmit NMEA format GPS data to another device.  The four wires for the com port are combined with the Power Supply cable and NMEA 2000 Power cable to form the power/data cable (shown earlier). Com-1 uses the yellow wire to transmit, the orange wire to receive and the shield wire for signal ground. Your unit does not use the blue wire.

The M7 DB9 Serial Connector

The 9-pin serial I/O connector to the M7 is a female 9-p D-subminiature connector having the following pins configuration.

Front-view of DB-9 connector on modem (female)

Wiring the DB9

The Lawrence’s “Data Cable” must be connected to the M7 transponder.  This connection will allow the M7 to put icons on the screen of the Lowrance display, showing the location of other tracked vehicles.  The Raveon M7 GPS transponder uses a 9-pin “DB9? connector to connect to the Lowrance.  Solder the Lowrance data cable wires onto a DB9 connector and plug the DB9 into the M7 transponder as shown below:

The orange wire goes to pin two of the DB9, the yellow wire to pin 3, and the shield braid of he cable connects to pin 5 of the DB9.  The blue wire is trimmed off.

The extra wires on the Lowrance display called NMEA 2000 power are typically not used in a vehicle installation, and may be wrapped up with electrical tape and tucked away.

Configuring the Lowrance

Set the NMEA communication of the Lowrance to 4800 baud.  System Setup >  Communications Port.  Enable NMEA 0183 input and set the baud to 4800.

Configuring the M7 GX Transponder

Raveon has a designed the M7 GX transponder to work with Lowrance Display or any other NMEA 0183 display that can accept the “$GPWPL” NMEA message.   The $GPWPL is an industry standard message that the Lowrance displays and many other GPS displays interpret as a waypoint command.  The M7 GX outputs this $GPWPL message to put icons on the screen of the Lowrance, and to move the icons around on its screen.

To configure the M7 transponder to output the $GPWPL message, set the M7 GX to GPS mode 2.  To do this, put it into the configuration mode by send the +++ into the serial port.  The M7 will respond with an OK.  Type GPS 4 and press enter to put it into GPS 4 mode.  GPS 4 is the mode that causes the M7 GX to output $GPWPL messages whenever it receives a status/position message over the air.

How Far Can I track my Vehicle?

A quick answer: About as far as a standard voice radio will allow you to talk.

In flat wide-open areas, such as deserts, grasslands, and farms, vehicle-to-vehicle communications will be 2 miles on the low end and often as much as 10 miles on the high end. A base-station, either with a 15-meter tower or placed on a local hill, will reliably communicate out to 10 miles, and often out to 20-30 miles.

In a rolling hills area, such as much of Nevada, Wisconsin, or Baja Mexico, vehicle-to-vehicle range will be 1-2 miles as long as both vehicles are not in a valley. The range will often go up to 15+ miles as both vehicles crest hills. A base-station, either with a 15-meter tower or placed on a local hill, will reliably communicate out to 7 miles, and often out to 20-40 miles.

In mountainous areas or wooded hills, such as much of Colorado, Tennessee, and northern California, vehicle-to-vehicle range will be ½ – 5 miles and will also be very sporadic depending on the terrain between the vehicles. The M7 GX takes advantage of this by frequently reporting its position, so that as vehicles crest peaks, they can receive location transmissions from a long way away. Often the vehicle-to-vehicle range will be as far as 15+ miles as the vehicles both crest hills. A base-station placed on a mountain top can extend reliable communicate out to 10+ miles, and often out to as much as 50 miles.

In urban areas and cities, structures will create multi-path and interference, reducing the usable range. Communications will be very similar to operation in rolling hills. Vehicle-to-vehicle range will be 1-3 miles. A base-station either with a 15-meter tower or placed on a local hill, will reliably communicate out to 5-7 miles, and often out to 10 miles.

Raveon Technologies Corporation

990 Park Center Drive, C
Vista, CA 92081
sales@raveontech.com
760-727-8004

If you are using an Intel Atom motherboard and processor combo as the base station for a Ravtrack vehicle tracking system, the computer may not boot properly due to the radio supplying a signal on the DB9 connector to the RD input of the computer.  When RD input (pin 9 of the DB9 RS232 serial connector) is powered as the PC boots, Intel motherboards have problems booting.  There are 2 different ways to go about fixing this problem. The simplest one is to unplug the serial cable from the radio at boot and then plug back in once computer is booted. The other option is to cut one of the wires in the DB9 ribbon cable.  To do the second option, first open up the computer case and locate the serial cable that goes from the com port on motherboard to the radio.

Once you have located the cable, next take off the cover of the DB9 cable on the other end where it plugs into the radio to expose where the ribbon cable is soldered onto the connector. This is where we cut the cable so as to keep it covered and looking clean.

The wire needing to be cut is the second one from the right when looking at the connector from the bottom. It is recommended that you take out a small section of the wire so as to not risk any accidental contact.

Antenna Tuning or Cutting

Selecting and installing a proper antenna for a telemetry radio, GPS transponder, or base station involves selecting a suitable style of antenna for your installation, properly mounting the antenna, cabling the antenna to the radio connection, and possibly adding a lightning arrestor to the antenna cable.  One of the most important considerations is ensuring you select an antenna that works well for your operating frequency.  In many cases this involves tuning the antenna for the proper frequency.

Any antenna is constructed of a metal conducting element.  Often this element is insulated from direct contact with a rubber or fiberglass sheath, or some other material and you will not see the metal element itself.   In any good antenna the shape and length of the element was carefully considered when the antenna was designed.  Some elements are simple straight thin metal rods, others are coils, loops or other styles or combinations.  Frequently the antenna is built to work at a very specific frequency or range of frequencies, such as 450-460MHz.  If you select an antenna built for the wrong frequency you will have very poor results.

Some common antennas allow for the user to adjust the antenna for their frequency.  The antenna may be built to cover a wide range of frequencies, such as 400-500MHz, but should be adjusted to the precise user frequency.  As radio transmissions are actually radio “waves” you may remember that a radio frequency and radio wavelength are tightly related.  Tuning an antenna typically involves adjusting the length of the conducting element(s) to be a specific ratio of the actual radio wavelength.

Often field tunable antennas involve 2 elements that are allowed to slide or telescope back and forth to achieve a specific antenna length.  In other cases the element(s) may need to be physically cut or altered to a specific length.   In the case of a common omni-directional fiberglass antenna the metal element(s) are housed within a fiberglass insulative sheath, and must be removed from the sheath to gain access.  Here the user must expose the metal conductive element(s) and cut them to the proper length.  If the antenna has multiple elements , each element may require a different cut and re-assembly must place them in proper order.

To physically cut the element(s) a good metal file, Dremel tool, or fine tooth metal saw may be used to cut the element(s), or score and snap them carefully.  Once done the element(s) go back into the fiberglass sheath in correct order.  You can smooth any sharp points first if you like.

 If an antenna is meant to be tunable it will come with a chart or other instructions as to what length is intended for a specific frequency, and perhaps instructions on how to physically perform the cut or adjustment.  If  you intend to cut-to-tune your antenna remember these 5 key points:

• Never cut an antenna unless you are certain you need to do so.
• Make sure you have clear instructions on how to measure and cut the antenna for your frequency, and measure very carefully.
• If the antenna contains multiple elements, plan and track each element with individual care.
• Wear eye protection and follow any safety procedures.
• Never cut the element too short.  It may be better to take it increments at a time to achieve proper length.

If you order an antenna from us that requires cutting, we are happy to do this for you prior to shipping if you can tell us the precise frequency you need.

RavTrack from Raveon Technologies Scores a Hole in One

Introduction:

As the demand to improve the “playing experience” at golf courses and country clubs continues to grow, course managers are adding new technologies to enhance their product while also adding to their bottom line.  One of these methods gaining traction is GPS tracking of the golf carts (and in essence the golfers) on the course to enable better management of tee times, tracking of course bottle necks, improved beverage and snack service, downloadable advertisements, quicker servicing of failed and dead battery golf battery golf carts, on-the-go diagnostics, and cart misplacement/theft management.  For the golfer, the course owner can now also have the ability to provide (free or at a cost) statistics, shot history, distance to pin, and other limitless features that improve the golfing experience for the novice and the professional.

Methodology:

Global Positioning Satellite, or GPS is at the heart of all golf cart-tracking systems.  GPS enables a unit to pinpoint its position on planet earth using a combination of satellite transponders and ground based radar.  The three most common methods used for transmitting the gathered GPS data at golf courses include cellular, WiFi, and Narrow band VHF/UHF radio transmission.

Cellular systems use the same radio solution as does your standard cell phone/smart phone.  The cellular solution’s benefits include low power operation, high data rates, and direct connection to an “App”, while the disadvantages include the need to have cell service in the area where the golf course resides, each cart to have a monthly subscription service, dependency on a third party carrier, outages, limited service during “busy” cell phone times, and reduced accuracy (if the cell signal itself is used for GPS triangulation).

WiFi uses a radio solution similar to what many folks use in a coffee shop or in their homes to connect to the Internet in a wireless fashion. The WiFi solution’s benefits include free connection, low power operation, and high data rates while the disadvantages include very limited range without a repeater, loss/weakening of signal due to obstructions, reduced throughput under heavy course loads, a max number of nodes supported, and interference from other WiFi devices in proximity to the course/golf cart.

Narrow band RF data modem solution, like that from Raveon Technologies RavTrack solution, use a dedicated UHF/VHF RF link similar to that in use fire/rescue/military communications links. The RavTrack solution’s benefits include free unlimited data connection, ownership of the frequency band, no third party control of the network, long distance range without a repeater (can cover the whole course), accurate (up to a meter) tracking, and an unlimited number of nodes supported while having virtually no disadvantages or limitations.

The RavTrack Solution:

The RavTrack solution from Raveon Technologies is a self-contained hardware and software package that can be customized to support unlimited applications in the gold cart tracking space.  Using a ruggedized and pre configured radio transponder in each golf cart along with a transponder and software command and control at the club house (no internet connection is required), each golf cart can be pin pointed and tracked on the course using customized maps and/or standard google type maps. “RavTrack PC” software is provided with the solution along with mapping/tracking support from popular third party software houses. The software provides such features as position, custom icons for each individual cart, programmable geofencing parameters, collision detection/avoidance alerts, distance between various carts, unlimited logging and history file generation, and several other position related parameters. Raveon can also provide customizable apps and solutions to better support the course operators exacting needs.

The RavTrack solution can support all the features discussed in the introduction of this article along with an unlimited number of customizable applications. These features will enable the golf course/country club to differentiate itself from competing courses by improving the golfers experience (statistics, distance to pin, shot history, etc.) while improving the courses bottom line by better managing its carts, its queuing of tee times, advertising, instantaneous cart down time and location management, and potential revenue generation by charging for statistics and print outs for the golfer.

Conclusion:

The RavTrack solution from Raveon Technologies emerges clearly as the best solution for providing a low cost and easily manageable environment for the golf course/country club owner. For more information or a quote, contact Raveon Technologies at 760-727-8004 or check them out on the web at raveontech.com.

The RavTrack Atlas PL personal GPS locator radio network capabilities

Most people will identify the Atlas PL personal locator as an excellent device for people to wear and to send GPS position information, alerts, and man-down status.  Typically the Atlas PL is used in conjunction with the RavTrack AVL GPS vehicle transponders which are equipped in fleet vehicles and used for base receiving stations as well as store-and-forward repeaters.  It is common for these latter transponders to be used to complete a GPS tracking radio network for tracking both personnel, and vehicles, or other costly assets.

However, it is also possible for the Atlas PL units alone to be used to construct a GPS tracking network complete with multiple base stations and/or a repeater, without the involvement of the vehicle transponder models in the system.  The Atlas PL inherently has all the capabilities of the vehicle based models.  Releasing these capabilities is simply a matter of following correct configuration procedures for the Atlas PL.

The following diagram demonstrates the use of the Atlas PL in its traditional role as a personal GPS transponder but also as multiple base stations, with one base station also serving as a repeater.

Within each box are typical settings of the Atlas PL as part of the GPS tracking scheme.  Above each box are the intended uses of each Atlas PL in the tracking network, while below each box are a series of configuration commands the user should issue to each Atlas PL unit to configure each unit for the particular use specified.  Finally, alongside each command is an indication of what that command actually configures in the Atlas PL.

Each Atlas PL starts out in GPS mode 8.  This configures the Atlas PL to function in the most common transponder configuration and enables the advanced battery management functions of the Atlas PL as well.  However, it is important to note that the command GPS – such as GPS 8 – is a macro command which configures many different aspects of the unit.  Most commonly the GPS command is understood by the user to set the format of the NMEA output, but it in fact does much more.  For instance, issuing  the command “GPS 8” to an Atlas PL will completely turn off the receiver circuitry of the unit. This is not what we need for a base station receiver or repeater.  The subsequent commands change other configurable attributes of the Atlas PL, overriding the macro set of configuration parameters, to arrive at the final desired configuration.  It is critical these configuration commands be issued after the GPS command.

We hope this demonstrates some of the capabilities of the Atlas PL not commonly identified by the end user.  Should you have in mind a specific function of an Atlas PL that is not apparent, we encourage you to contact us.

Fast GPS reporting with TDMA timeslots

RavTrack is very fast at reporting the positions of even large fleets over a single radio channel because each RavTrack transponder is assigned a specific time slot in which to transmit, avoiding interference which may occur if multiple devices were permitted to transmit simultaneously. The fact that all transponders share a “common clock” via the GPS satellite signals allows us to assign a unique timeslot to each device, yet maintain timing coordination over a large fleet of devices.

RavTrack timeslots are built on 50 millisecond increments by factory default, athough 10msec granularity can be achieved with newer firmware versions. For the purposes of illustration we will assume each time slot must be a multiple of 50msec. The specific size of your time slot is typically determined by the bandwidth/transmission rate of your particular transponder and the presence or absence of a repeater.

Most FCC licenses granted in the USA are for narrowband (12.5KHz) channel spacing. The associated RavTrack transponders operate quite well at 4800 baud transmission rate (factory default), although slower rates can be used. These transponders can complete a position report transmission in about 64msec, so a 100msec timeslot would be the factory default when no repeater is in the system. If your license permits wideband (25KHz) channel spacing, and your transponders are capable of wideband operation, the factory default transmission rate is 9600 baud. In this instance a position transmission can be completed in about 32msec, so a 50msec timeslot is typically used when no repeater is in the system.

If your system uses a store-and-forward repeater you need to make each timeslot longer so that once a vehicle reports, the repeater has sufficient time to receive, process, and repeat the transmission on “quiet air” before the next vehicle transmission occurs. In a 9600 baud system a 100msec timeslot may be used if you are not encrypting your transmissions, but with encryption a 150msec time slot should be used, as the repeater needs a bit more time to process an encrypted message than an unencrypted message. In a 4800 baud system using a repeater a 200msec timeslot may be used whether or not you are encrypting the position transmissions.

Timeslots are numbered starting at zero, and the zero time slot is reserved by the system. Thus you can start numbering your transponder time slots at slot 1 (0001). In a system using 100msec timeslots the first second is completed once time slots 0 through 9 are used (10 time slots total). For this reason, up to 9 vehicle transmissions can be completed in the first second, and in this example your fleet size would be limited to a total of 9 vehicles if you need the entire fleet to report each second. As the reserved zero time slot only occurs at the start of any particular TDMA cycle, cycles longer than 1 second would allow the addition of 10 more time 100msec slots for each second added to the cycle. Thus a fleet using 100msec time slots can provide reports from 19 vehicles every 2 seconds, 29 vehicles every 3 seconds, and so forth. Similar logic applies to other RavTrack timing schemes.

If your fleet is quite large and you want faster updates than the 100msec timeslot scheme allows, you can double your fleet size if local regulations allow you to use wideband transmissions that yield a 50msec time slot.  In many deployemnets a fleet can scale much larger and still preserve fast report cycles simply by using multiple frequencies.  As transponders on different frequencies will not interfere with one another even if transmitting simultaneously, a properly architected system using five frequencies can report five times faster than the same system using only one frequency.

When setting up your fleet timing it is a good idea to leave a little extra capacity in your timing scheme to allow the easy addition of new vehicles to the fleet.

Finally, if you want to use the RavTrack transponders to transmit not only position data, but extra data as well (e.g. from an on-board telemetry device), you will need longer time slots to send this extra data. Please contact us in this regard, and we are happy to help you in architecting a solid system.

For a more technical programming perspective on TDMA time slots as used by RavTrack see the following articles: http://ravtrack.com/GPStracking/tdma-transmission-overview/361/  

http://ravtrack.com/GPStracking/tdma-time-slots/71/ 

or consult your technical manual.

How do I rectify an image file and convert it to a Geotiff?

Raveon’s customers have a wide variety of applications for our GPS tracking system. Whether you run a golf course consisting of a few dozen vehicles, or a large fleet that spans an entire city, you may find that you require a specific image for use with the RavTrack Software. The following is an example of how to rectify an image. Rectifying an image translates into the process of converting a standard image into a usable map coordinate system. The map coordinate system will output in the form of a Geotiff file that can be loaded into RavTrack. Our example will be of a simple map image of Vista, Ca. We will use Global Mapper 12 to rectify the image.

1. First start Global Mapper 12 and select download free maps. Select an aerial map or street map, depending on the image you are trying to convert. Download only the area that you are trying to cover. This will be your reference map coordinate system.

2.  Now select rectify imagery under the file tab.

3. Set the configuration with Export and Geotiff selected as shown in the following image. Then select OK.

4. Determine the location of your map image and open it.

5. The image rectifier will open. We will began the process of selecting ground control points on our reference aerial map, and matching the point on our image. This will allow the image rectifier to know the geophysical location of the points on our map. With at least three of these points, the image rectifier will be able to convert the image to a usable Geotiff file for us to use with RavTrack.

6.  Set the projection by selecting the option in the bottom right of the screen. Configure the projection to match your reference coordinate system. Then select OK. For our example we are using UTM zone 11.

7. Find an area on your map image that you can locate as well on your reference coordinate system. Set a ground control point on the reference coordinate system by clicking on the location. Find the exact location on your map image and set the equivalent ground control point.

It is important to ensure that the locations match. You may have to zoom in or out in order to achieve the best match.

Once done, select add point to list. Do this for three different locations that are spaced far away from each other. For example, a control point in the upper left hand side of the image, the upper right hand side, and the center of the map.

8.  Once you have at least three ground control points, select OK. Your image will be converted to a map coordinate system and stored in the same directory from which your map image was retrieved.

For more information on how to use Geotiff files with RavTrack PC, or for more information on UTM zones, please refer to our Tech Blogs in the Map and Imagery Section.

Raveon’s RavTrack GPS tracking system is the ideal golf cart tracking system to track golf-carts and golf course maintenance vehicles. Golf Cart Tracking

RavTrack GPS tracking delivers helpful, real-time location information and displays it on a map image of your golf course. You can track the carts, mowers, trucks, and workers.  You can see where you mowed each hour, day, or week. You can quickly locate carts to deliver food and beverages.

It also can detect potential theft or abuse of your carts and equipment.  You can configure keep-out zones and many other rules to notify the ranger or security if a rule is violated.

Because Raveon’s RavTrack system uses VHF and UHG licensed UHF radio frequencies, you can easily cover your whole course and have no monthly air-time fees.  The RavTrack system is also available on the VHF MURS radio band, which is license-free.  It works where GSM radio-based systems don’t and because the airtime is free, your update-rate of cart position and status is the fastest in the industry.  You can easily track 75 carts with 15-second update rates.

And unlike the short-range 900Mhz and 2.4gHz solutions, RavTrack will cover your course, and reliablye show you where your vehciles are.

RavTrack GPS tracking improves golf course operations by:

A comparison of GPS tracking and AVL systems.  RavTrack versus cellular GSM or GPRS.

Most GPS tracking systems use a “cellular” wireless telephone carrier system to collect position information from the fleet in the field and transport that information back to headquarters.  You may see acronyms such as GSM or GPRS describing the system.  The RavTrack system uses a very different approach, that of local user based radio.  These two approaches will often appeal to different types of users.  However, one thing is clear; if RavTrack can meet your needs it is by far the superior choice over cellular.  Here are some of the most common reasons why.

Total cost of ownership

Every cellular system has recurring service fees, typically on a per vehicle per month basis.  The RavTrack system has no monthly fees.  Consider how long they will want to have a tracking system.  Likely you will want it “forever” and you should recognize that once you have RavTrack installed you have no more expenses.  In some cases it may cost more to initially purchase and install RavTrack versus a cellular system but over several years time it can cost much less, even if the monthly fees the operators charge are not very high. 

Also, RavTrack protects your tracking system from budget cuts.  If you determine RavTrack and the celluar systems both cost the same over 3 years, RavTrack is the only of the two systems you know you can keep.  If you are forced to cut your budget next year or later, then your cellular system, and any investment you have made is at risk.  RavTrack is not at risk.

Performance

RavTrack will provide very frequent and very fast updates.  Both are important.  With RavTrack you can hear back from the fleet at very frequent intervals.  How does this compare to the cellular system?  Perhaps you feel frequent updates are unimportant, but if later things change can the cellular system even provide these faster updates?  If so, does the monthly charge increase?

RavTrack updates are not only frequent but fast as well.  When a vehicle sends the current position with RavTrack you can receive this position right away (often less than one second later).  Many cellujlar systems will take 15 seconds, 30 seconds, or even several minutes before the operator receives the position report from the vehicle

Both of these factors are important to operations that serve in emergencies such as police, fire, and ambulance.

Capability

With RavTrack you can track fleet fleet or personnel from other vehicles or mobile posts?  Any RavTrack vehicle can receive from the other vehicles or personnel automatically, and with a proper display can see the other members on a map in real time.  Even personnel on foot can be provided a hand-held display.  Almost no other system has this capability.  This is an important benefit to supervisors in the field or any time teams need to work together.  You can have this capability now, or add it later.  You do not lose this capability, nor general tracking capabilities if part or all of your fleet travels into an area where cellular service is not available.

Reliability

The celllular service is a shared service used both for voice and data.  Any high demand or peak use of the cellular system, either at a single receiver or on the system overall, such as can be caused by a disaster or just a popular event, can overwhelm the cellular system and may cause the system to be too overloaded to be useful for tracking.  Often, this occurs when you need your tracking capabilities most.  The RavTrack system is dedicated to your fleet and not subject to peak use concerns.

Security

RavTrack messages can be encrypted with 128 bit AES, making them indecipherable to outside parties.  Furthermore, RavTrack data is stored only on the customer devices and not available to unauthorized users, including those that might be in a 3^rd party data center.

Powerful Software

RavTrack PC software is extremely rich with features, unmatched by most other software packages.  RavTrack provides extensive geofences, rules, and alarm capabilities.  RavTrack PC enables sophisticated user security measures to ensure only the right people have access to important information, and features in depth historical logging, playback, and reporting capabilities.  For a detailed list of RavTrack PC features and functions refer to http://ravtrack.com/RavTrack-PC-Functions.html

Flexibility

As the customer you are always in control of the RavTrack system and can make adds, deletes, and changes whenever you need.  You do not have to submit a request to a vendor and wait for the vendor to perform (or mis-perform) on either routine on uncommon requests.  Furthermore, as a RavTrack software implementation is specific to each customer and not shared, we are capable of providing you something unique or special to meet your individual needs, and do not need to be concerned about a specific change affecting other parties.

Adaptability

With RavTrack you are not limited to the map your vendor provides.  Almost any map can be converted into a RavTrack map, including aerial photographs!  Choose the map or view that best meets your needs, when you need it.  If your environment changes RavTrack allows you to bring in the latest map with the latest data, providing uncompromised adaptability.

Options

The RavTrack system is supported by more than 10 other software packages from parties other than Raveon, giving you far more choices than any other system on the market.  Most cellular systems provide only one software option.

The RavTrack system includes devices for both vehicles as well as personnel.  Many other systems only provide equipment to track vehicles.

How can I convert this high precision map that I used with my previous tracking software, the map info is stored in .dat format?

We can easily convert over data files that have stored map information. We will use Global Mapper 12 to load the files into our editable area, set our projection, and then export as a usable Geotiff. We will then convert that Geotiff into .Maplib Format.

The following steps outline the procedure:

1. Start Global Mapper 12 and select (Open all files in a Data Tree).

For our example, we have have a set of data files stored in a local directory. Select (open all files in a directory tree) and choose the directory your files are stored in.

2. Set Options for your .Dat File

The ASCII options window will show for each data file that loads. For our example, we will leave the default values and select OK. Repeat this for each Data File that loads. Note, depending on the data file and stored vector data, not all data may successfully transfer over. You may see a window that asks "Cancel all remaining data file loads", select no and continue loading your files.

3. Map is Now Loaded Into Global Mapper.

The data files have successfully loaded. We can now edit and export the map image.

4.Set Projection

We must now set the correct projection. Select (Configure) under the Tools menu. Then Select the (Projection Tab). Set the projection and zone your map covers. For our example we are using UTM, ZONE 50. There are many reference maps that can be found online with outlined UTM zones. It is very important that you select the correct projection and zone in order the the exported map image to be usable with RavTrack PC. Select OK when finished.

5. Export Geotiff

Select (Export elevation grid format) under the file menu. In the following windows select Geotiff as your export format. We will now export the map file.

6. Select Output Options

The export options window will allow us to adjust the output settings. Our focus is on the sample spacing/scale option, and the world file option highlighted in the above screen shot. The scaling option will allow you to adjust the output resolution of your image. Increase the values for smaller resolution maps, and decrease these values for larger resolution maps. Select the generate world file option and click OK. Save to a known directory that you can easily find again.

7.

Open RavTrack PC. Click (Map Creation Tool) under the tools menu. We will now take our Geotiff and convert it to .MapLib. Select (New Map).

8. Select your .tif Image

Find the directory in which you saved your Geotiff. Select and open you .tif image.

9. New Map Settings

Leave the new map settings defaulted and select OK.

10. Set Projection Settings

Set the Country, Grid, and Zone that the map covers. Note, these parameters must match the settings you placed when creating the Geotiff. Select Next when complete.

11.Save Your MapLib

Your Geotiff has now been converted. Select (Save Maplib as) under the file menu. Save your completed map into your RavTrack PC map directory. This directory location can be found by selecting Help>About RavTrack under RavTrack PCs help menu. After the Save is complete, exit the map creation software.

12. Select Your New Map

Your Map is now ready to be used with RavTrack PC. Select (Program Properties) under the file menu in RavTrack PC. Your map should be located in the lower left hand area of the window. Select your Map and click Save and Exit.

13.Success!

The conversion is complete. Select (Go to Map) under the view menu. Center your map, and your done.

INTRODUCTION:

WASS (Wide Area Augmentation System) is the next generation standard for implementing higher accuracy GPS systems. As demand for GPS continues to grow, the US government has implemented a more robust system to meet the needs of next generation tracking and improved reliability while still maintaining standard equipment in the field. Raveon Technologies has taken advantage of this new standard by adding WAAS to both their M7 GPS transponders and their industry leading RavTrack precision tracking solution.  

BRIEF HISTORY OF LORANC/GPS/DGPS/WAAS:

In an effort to support military and commercial aircraft, LoranC was the first implementation of modern GPS technology. Employing multiple ground based radar towers (sometimes compared to as bowling pins) typically near airports and larger cities, LoranC provided excellent positioning for its time as a method to keep track and position aircraft. The downside of LoranC was that it was less available in rural areas and completely unavailable over large bodies of water. LoranC was also not accurate enough to support extremely bad weather and non visual approaches.

GPS technology was next on the scene providing a 10x and greater improvement of positioning while solving the aforementioned approach problems. Using satellites and a low cost receiver approach, GPS took tracking from an expensive professional solution to a system that is now available in most cars, watercraft, and personal equipment.

Adding a differential mathematical approach, a specialized receiver, and land based FM towers, DGPS further improved positioning by another 10x. The downside of the approach is that it relies on line-of-site (to the towers) and provides spotty coverage in smaller towns and rural areas that don’t have the luxury of piggybacking on towers of local FM radio stations. Also of note is that a DGPS receiver is not compatible with a off the shelf consumer GPS unit.

WAAS is the latest approach and by far the most accurate. Using a combination of GPS satellites, ground stations, and geo-stationary satellites (see below for greater detail), accuracies up to less than 1M can be attained using standard off the shelf GPS equipment. With this type of spec, WAAS allows for new markets and solutions requiring a higher level of accuracy previously unattainable with existing solutions.

Some of these markets that Raveon Technologies WAAS enabled GPS transponders now support include vehicle collision avoidance, precision vehicle tracking and navigation, tighter and more specific geo-fencing, more accurate personal tracking, precision agriculture plotting, along with several other position dependent solutions.

TOPOGRAPHYOF A WAAS SYSTEM AND HOW IT WORKS:

WAAS is a combination of ground base stations and satellite transceivers used to greatly improve the accuracy and performance of conventional GPS. Conventional GPS relies on using satellite transceivers “only” which are subject to ionosphere disturbances (billows), satellite orbit errors, timing, and clocking errors. By augmenting ground based stations, the errors associated with GPS are greatly minimized if not eliminated while also adding monitoring and real time adjustment of the GPS satellites themselves.

The system installed in North America is as follows: 35 plus ground base stations called Wide area Reference Stations (WRS) along with the existing satellites provide correlation data that is sent to 2 Wide area Master stations (WMS) on each coast to create a corrected signal. This corrected signal is then retransmitted by a geo-stationary satellite called a Ground Uplink Station  (GUS) that is fixed at the equator.

The system provides for guaranteed accuracy of  3 meters or less with typical accuracies approaching sub 1 meter (multiple samples may be accumulated to achieve even better specs). Adding to the accuracy improvement, uptime approaches 99.999% with a downtime of 5 minutes per year while conventional GPS can only guarantee 4 days per year of downtime.     

SPECIFICATIONS OF WAAS VERSES STANDARD GSP, DGPS, AND LORANC:

The following is a table of specifications and observed lab measurements of the various positional methods used in the US. 

As can be seen from the table, Raveon Technologies WAAS enabled transponders provide the most accurate tracking and positioning available while employing standard GPS gear. DGPS comes in at second, but as discussed, is only employed and is dependable in cities and urban areas where FM towers are available and line of site can be attained using the specialized DGPS gear. Standard GPS will continue its success in supporting the large consumer but lower precision auto, marine, and personal tracker market. LoranC, although the least precise, has a large installed base in the personal and small aircraft segment. 

Below is a comparison of the position error of a GPS tracking system using WAAS augmentation and DGPS.  In this test, the horizontal accuracy was very good with each method. The WAAS system had much better verticle accuracy. 

CONCLUSION:

By implementing a WAAS GPS M7 or RavTrack system from Raveon Technologies, precision accuracy approaching sub 1 meter is attainable and repeatable using existing GPS receiver systems allowing for new applications and end-products in the positioning and tracking space.

The purpose of this tech blog entry is to guide a RavTrack PC user in acquiring a usable Geotiff Map File from Global Mapper 12. This Geotiff can be converted to .Maplib format and displayed on RavTrack PC.  Please note that earlier versions of Global Mapper, including version 10.02 and 11.00, can be utilized for the same operation, however, some specific  WMS data sources are not built in.

Global Mapper 12 is a powerful mapping software that allows access to high resolution geospatial imagery which can be downloaded, edited, and extracted. We are going to focus on the downloading and extracting aspect of the software.  Most RavTrack users have applications that require the use of street, satellite (Aerial), topographic, and similar maps. Obtaining these maps can become somewhat difficult; however, with software packages such as Global Mapper, you can easily obtain a usable Geotiff that can be displayed on RavTrack PC.

To accomplish this please follow these steps:

1. Start up Global Mapper 12.

Ensure you have the registered version. The trial version may limit your ability to extract the geotiff map image.

2. Select (Download free maps/imagery)

Select the type of map you wish to use. Common maps include openstreetmap.org and NAIP Color Imagery. Enter the area location details in the (Select download area) section. The amount of area selected is proportional to download time, larger areas will take longer to process and download.

3. Configure Projection

After your map image has loaded on the screen, select (Configure) under the tools menu.

4. Set the Projection Parameters.

Select (UTM) and the (Zone) for your map’s area. There are many reference maps online which outline the UTM Zones. For our example we are using UTM projection in Zone 11. After you have selected UTM and your Zone, click (OK). Your map is now in the correct projection.

5. Select (Export Raster/Image Format) in the file menu.

Your Map is now ready to export. Ensure you have selected the area you wish to cover.

6. Select Geotiff as your export format.

7. Set Export Options

This is where you can adjust the map image you are exporting. For our example we are going to focus on the (Sample Spacing/Scale) and (World File) option. The scaling option allows you to control you resolution. If you wish to have a high resolution map (More Detail and lower elevation) decrease these values, for lower resolution and a smaller map file, increase these values. Ensure you select (Create TFW (World File)). Once this is done, click OK.

8. Start RavTrack PC and select Map Creation Tool

After the Geotiff export is complete, open RavTrack PC. Select (Map Creation Tool) in the tools menu. We will now begin to convert the Geotiff to a usable RavTrack Image (.MapLib format).

9. Select New Map

This is the map creation software that will convert the geotiff to .maplib.

10. Select the Geotiff Image

Find the directory of the Geotiff image and select the .tif image that exported by Global Mapper. Once selected click OK and the geotiff will be loaded into the map creation tool.

11. Select OK to the Default Settings.

Click OK to the default settings here and select OK.

12. Click Yes to World File

The map creation tool will ask you wif you would like to use the world file you selected in Global Mapper. Click Yes.

13. Select Grid

This section is vital, incorrect values will cause the map image to display incorrect coordinates. Enter your (Region), (Grid), and (Zone). For our example we are located in the United States, using UTM North, and in Zone 11. Once complete, click next.

14.Verify Coordinates

You have completed the conversion process. Click anywhere on the map and the coordinates of that location will display on the lower left hand side. You can verify these coordinates by referencing them with known locations from an alternate source such as Google Earth.

15. Save your Map

Select save MapLib as under the file menu.

16. Locate your RavTrack Map Directory.

Locate your RavTrack PC map directory. You can find the specific location of this folder by selecting ABOUT RAVTRACK under the RavTrack PC help menu. Save your .MapLib.

17. Open Program Properties

Open Program Properties located under the file menu in RavTrack PC. Your Map will be located on the lower right hand side. Select your Map file and click save and exit.

18. Success!

You have successfully converted a Geotiff to .Maplib. If your map does not show on the screen immediately, select VIEW>GO TO MAP. Your map will display and you can now use it with RavTrack PC.

So, you set up RavTrack PC and connected your base station to the computer running RavTrack PC.  And yet, nothing is happening. This article describes some common solutions to communication problems in a RavTrack GPS tracking system.

Connection/COM port issues

When the system is running, select View > Communication Statistics from the main screen.  This will show you how the various RavTrack PC communication channels are operating.  In the second column of the communication statistics is a message counter with two numbers AAA/BBB.  AAA is the number of NMEA messages from the local radio connected to RavTrack PC.  BBB is the number of PRAVE messages that came into RavTrack PC through this channel.  A PRAVE message occurs whenever the “base” radio receiver connected to RavTrack receives a GPS position report over-the-air.

If the message counter shows 0/0, then there is no communication with the base radio.  This is probably due to on of the following things, and will have to be remedied:

1. The Base radio is off.
2. The base radio is not connected to the PC running RavTrack PC.
3. The COM port that the base radio is plugged into is not configured correctly (Program Properties > Congure I/O to repair it).
4. The cable connecting the base to the PC is bad, or is a “Null modem”. For most computers, the connection will be a USB or a 9-pin serial cable wired 1:1.
5. The COM port that the base is connected to is in use by another software program.

No Over-the-Air Reception

If the message counter in the Communication Statistics window shows  NNN/0 where NNN is some non-zero number, and the second number is 0, this means the base radio is communicating with RavTrack PC sending NMEA messages, but nothing is being received over the air.   The COM port and cables are fine, but there is a problem receiving the over-the-air messages.  The most common problems that will cause this and need to be corrected are:

1. No antenna is connected to the base radio.
2. The base antenna cable or connector is broken.
3. The KEYPHRASE is not set.  The KEYPHRASE encryption code must be the same in all radios.  The factory default KEYPHRASE is “RAVEON”.
4. The base receiver is not set to the correct frequency. Note: the base’s STAT LED will blink green each time it receives a message from a GPS transponder.
5. The TOID (ATDT) in the mobile transponders are not set to the base station’s ID.  Note: you can set the base station address mask to ATMK 0000 to receive all messages regardless of TOID.
6. The mobile transponders are not transmitting.  Reasons for them not transmitting may be:
   A. No power to the transponder.
   B. No GPS satellite lock.  The transponder’s GPS antenna must be able to see the sky.
   C. The transmit frequency is incorrect.
   D. The KEYPHRASE is wrong.
   E. Their antenna or coax cable is broken or disconnected.

Common Configuration Errors

From the factory, all Raveon GPS transponders and base stations are configured to work out of the box.  You will not need to set anything just to verify they work.  But, you may bave to modify some settings for your particular installation before you put them in the field. The following parameters within the base station and GPS transponders must all be set correctly and to the same settings on all units for your system to work:

1. KEYPHRASE
2. Over-the-air baud radio. Do not change without consulting the factory.
3. TOID of the transponder must be the ID of the base.
4. Group number (ATGP).  The factory  default is none, and is typically left at none (ATGP 0).
5. TDMATIME and SLOTTIME parameters.

The U.S. Department of Commerce requires that all exportable GPS products contain performance limitations so that they cannot be used in a manner that could threaten the security of the United States. The following limitations are implemented on the Trimble Copernicus receiver receiver.

Immediate access to satellite measurements and navigation results is disabled when the receiver’s velocity is computed to be greater than 1000 knots, or its altitude is computed to be above 18,000 meters. The receiver continuously resets until the COCOM situation is cleared.

If the Raveon GPS transponder will be used in aviation applications, the unit should be put into the AIR mode.  See the posting “gps-receiver-dynamics” for information about the AIR, LAND< and SEA modes.

The GPS receiver in Raveon’s M7 and Atlas PL GPS transponder may be configured for different situations. By default it is configured for LAND operation.
Selecting the correct operating parameters has a significant impact on GPS receiver performance.  GPS receiver dynamics may be optimized for LAND, AIR, or SEA operation.
  
  LAND  = 1    Maximum speed the GPS will receive at is 233knots/268mph/430kmh
  SEA = 2    Maximum speed the GPS will receive is not specified.
  AIR = 3   Maximum speed the GPS will receive at is 1000knots/1150mph/1800kmh
 
The default setting for the GPS receiver used in Raveon’s M7 series of GPS transponders and Atlas PL Transponders is LAND.
The default LAND operating parameters allow the receiver to perform well in most environments. Transponders with firmware version C12 or higher are able to view the GPS receiver’s configured dynamics, and change the dynamic mode between AIR, LAND, and SEA. Upon power up, the firmware reads the internal GPS receiver’s current configuration.

The user can optimize the internal GPS receiver in the transponder to a particular application.  If the receiver is then taken out of this environment, the specifically tuned receiver may not operate as well as a receiver with the default options.
The dynamics feature default setting is LAND mode, where the receiver assumes a moderate dynamic environment. In this case, the satellite search and re-acquisition routines are optimized for vehicle type environments. In SEA mode, the search and re-acquisition routines assume a low acceleration environment. In AIR mode, the search and reacquisition routines are optimized for high acceleration conditions. 

Reading the GPS Receiver Configuration

The GPS receiver configuration may be determined by using the GX command to show the overall configuration of the M7 or Atlas PL transponder. The “Dynamics” command will also return a string in the following format that indicates how the GPS receiver in the transponder is currently configured.   

MMM, EE.E, SS.S

 MMM: dynamic mode AIR, LAND, or SEA
 EE.E: Elevation Mask
 SS.S: Signal Mask  

Elevation Mask

This is the minimum elevation angle for satellites to be used in a solution output by the receiver. Satellites which are near the horizon are typically more difficult to track due to signal attenuation, and are also generally less accurate due to higher variability in the ionospheric and tropospheric corruption of the signal. When there are no obstructions, the receiver can generally track a satellite down to near the horizon. 

Signal Mask

This mask defines the minimum signal strength for a satellite used in a solution. There is some internal hysteresis on this threshold which allows brief excursions below the threshold if lock is maintained and the signal was previously above the mask.

Configuring the Dynamics

Use the DYNAMICS command to set or read the dynamics.  DYNAMICS with no parameter will return the configuration.  The following commands may be used to set the dynamics:

DYNAMICS 0    (factory default dynamic mode)
DYNAMICS 1    (LAND)
DYNAMICS 2    (SEA)
DYNAMICS 3    (AIR)

When issuing the DYNAMICS x command, give the GPS receiver a few seconds to execute it.  The M7’s firmware will also send a “flash save” command to the GPS receiver after the dynamics configuration is changed so that the change becomes permanent in the GPS receiver.  Upon power-up, the GPS receiver will use the new dyncamics setting. 

To verify the dynamics setting was saved, cycle power on the M7 or Atlas PL, enter the CONFIG mode, and enter the GX command to view the overall configuration of the device. The GPS receiver dynamics will be displayed.

Advanced GPS Receiver Configuration

To facilitate the advanced user, Raveon added a command “PASS” in the C12 firmware.  PASS will pass the parameter of the command to the internal GPS receiver in NMEA format. The GPS receiver used in the M7 transponder and ATLAS PL personal locator is a Trimble Copernicus II.  The technical manual for the Copernicus II contains details on how to configure it using NMEA type messages.  

For example, to set the GPS receiver to AIR mode, issue the following command while in the command mode.
    PASS $PTNLSCR,0.60,5.00,12.00,6.00,0.0000020,0,3,1

The command’s paramter is a NMEA formatted sentence without the * or the checksum.  The M7 or Atlas will append the * and the checksum to the sentence before sending it to the internal GPS receiver.  To set the dynamics, use the DYNAMICS x command, not the PASS command. The PASS command is provided to the advanced user who wished to reconfigure the receiver’s low-level configiruation paramters such as signal and elevation masks. 

If you change the GPS receiver’s configuration with the PASS command, do not forget to issue the save configuration command to the GPS reciever. The save command for the GPS receiver in the M7 and ATLAS PL is:
 PASS  $PTNLSRT,H,2,7,0

Overview

The M7 GX series of GPS transponders may be directly connected to a Garmin Oregon 450. When connected, the Garmin display map will show the location of the vehicle it is in PLUS the location of all other M7 transponders within radio range.  This unique feature allows one to quickly, easily, and inexpensively, make a mobile AVL system for tracking cars, trucks, race cars, construction equipment, or any thing Raveon’s M7 GX transponder may be installed on.

The Garmin Oregon 450 has a built-in interfaces for a “NMEA 0183? devices, which is another way of saying that they can connect to other devices using a serial cable.   The NMEA 0183 is an RS232 serial connection that typically operates at 4800 baud.  It is used to exchange way point and other information between displays, GPS devices, and transponders.

When Raveon’s M7 GX transponder is connected to the Oregon using the NMEA 0183 connection, the M7 transponder can put icons on the screen of the Garmin display.  As the transponder received updated positions from other vehicles, it updates the position of the icons on the Garmin display.

How NMEA 0183 works

Here is how their NMEA 0183 interface works:

NMEA 0183 Cable Connections

NMEA 0183 is a standard communications format for marine electronic equipment. For example, an autopilot can connect to the NMEA interface of a GPS and receive positioning information.  The GPS can exchange information with any device that transmits or receives NMEA 0183 data. See the following diagram for general wiring connections. Read your product’s owner’s manual for specific wiring information.

NMEA 0183 Wiring  (Data cable)

The Garmin Oregon 450 uses the yellow wire to transmit, the white wire to receive and the Black and green wire for ground.

The M7 DB9 Serial Connector

The 9-pin serial I/O connector on the M7 is a female 9-p D-sub miniature connector having the following pins configuration.

Front-view of DB-9 connector on modem (female)

Wiring the DB9

The Oregon’s “Data Cable” must be connected to the M7 transponder.  This connection will allow the M7 to put icons on the screen of the Oregon display, showing the location of other tracked vehicles.  The Raveon M7 GPS transponder uses a 9-pin “DB9? connector to connect to the Oregon.  Solder the Oregon data cable wires onto a DB9 connector and plug the DB9 into the M7 transponder as shown below:

The white wire goes to pin two of the DB9, the yellow wire to pin 3, the black and green wires get twisted together and both go to pin 5, and the red wire goes to pin 9 of the DB9. It is recommended that you keep the fuse on the red wire when setting up the DB9 connector.

Configuring the M7 GX Transponder

Raveon has a designed the M7 GX transponder to work with Garmin Oregon Display or any other NMEA 0183 display that can accept the “$GPWPL” NMEA message.   The $GPWPL is an industry standard message that the Garmin displays and many other GPS displays interpret as a way point command.  The M7 GX outputs this $GPWPL message to put icons on the screen of the Garmin, and to move the icons around on its screen.

To configure the M7 transponder to output the $GPWPL message, set the M7 GX to GPS mode 2.  To do this, put it into the configuration mode by send the +++ into the serial port.  The M7 will respond with an OK.  Type GPS 4 and press enter to put it into GPS 4 mode.  GPS 4 is the mode that causes the M7 GX to output $GPWPL messages whenever it receives a status/position message over the air.

Raveon Technologies Corporation

990 Park Center Drive, C

Vista, CA 92081

sales@raveontech.com

760-727-8004

With any complex communication system, there can be problems which cause it to not work as planned.  It could be a power failure,  electrical failure of a component, computer crash, cut cable, broken antenna, lightning damage, or a host of other unforseen issues.  Most of these are easy to deal with, but quickly being notified when they happen can be important.

You are able to monitor your GPS tracking system if your system uses RavTrack PC or any other GPS tracking software that allows you to create an alert if a vehicle does not report in.  By configuring your RF infrastructure components to also work as GPS transponders, the same tools used to monitor vehicles can be use to monitor your system.

For example, if you use a repeater in your system, configure it to periodially tranmsmit its GPS position also.  This way, if the antenna fails, power goes out, or it just stops working, your GPS monitoring software will send an alert.

With RavTrack PC, you can setup an Alarm and Monitoring Rule to help you monitor your radio network, server, or system operation.  Using the “No Reports” parameter monitoring feature, you can configure an alert to send an email to IP or Management personnel if your system stops working.

Monitoring System Components

To determine if part of all of the GPS tracking system is working, the periodic GPS position messages sent over the air may be monitored, and if they stop coming in, an alert can be generated to notify personnel of a potential system problem.

The easiest way to monitor the radios in your network is to configure them to report their GPS positions over-the-air.  Then configure an Alarm and Monitoring Rule using the No Reports parameter monitor to send an email if the item being monitored does not report in within a preset time period.  This will cause the Alert email to be sent if a part of the GPS tracking system fails such as broken antenna, cut cable, failed power supply, lightning damage, and unplugged serial cable.

Most radio transceivers, such as the M7 GX series of radios, which are used at a base station site may also be configured to output standard NMEA GPS position messages every 5 seconds.  This periodic local NMEA GPS message can also be used to determine if the base station radio is alive and operational.  To use the NMEA GPS position in an alert, you must configure the Communication Channel to interpret the NMEA GPS data as a tracked object in your system.  There is an option to Interpret GPS data w/o ID as ObjectData in the Systems Communications configuration tab.  If this enabled, RavTrack PC will create a new tracked vehicle with an ID 900X where X is the communications channel.  RavTrack PC will place the location of the vehicle 900X at its GPS position.

If there is a GPS transponder in the network that always is powered on and working, then the position report from that unit may also be used to check for system operation.

Monitoring a Server running RavTrack PC

The technique described above will work to monitor individual system components such as receivers, cabling, repeaters, and antennas.  But if a main server running RavTrack PC fails, the failed server cannot report itself failing.  A solution to this dilemma is to also run RavTrack PC on a management workstation, and then configure the same No Reports Alert on the workstation.  If the a server fails, causing the RavTrack system to stop recording GPS tracking data, the workstation’s No Reports Alert will then trigger, send an email, and/or alert the operator.

The M7 GPS transponders and the Atlas PL personal locators may be configured to output NMEA 0183 GPS messages from its internal GPS receiver.  For GPS tracking, these GPS transponders can receive GPS position reports from other radios, and they may also be configured to output their own GPS location via their serial port.

Following is a list of the NMEA messages that are available (as of revision C2 of the Firmware).

Refer to the product’s technical manual to see which NMEA messages are sent out in the various operating modes.  Once you set the “GPS Mode” of the radio using the GPS X command, you can change the NMEAMASK parameter to modify with of the NMEA sentences will come out the serial port.

For example, to have only the RMC sentence come out the serial port, use the following command”

NMEAMASK  256

To have the GGA and GLL come out the serial port use this command:

NMEAMASK 3

The NMEAMASK parameter is the sum of all of the decimal values of the individual bits corresponding to the NMEA messages.

It is usually possible to upgrade the RavTrack PC AVL software program to a newer version without re-installing the software as long as the major revision number is the same.  (2.6 to 2.7, 3.1 to 3.3 …)  Most upgrades can be performed by simply replacing the RavTrackPC.exe file which is stored in the program directory on your computer. This quick upgrade method avoids having to perform a full re-install of the RavTrack PC AVL software when simply upgrading to the current version.

To perform the quick update:

1. Close RavTrack PC.    File > Exit
2. Click on the link below to download a copy of the latest .exe file:
   http://ravtrack.com/downloads/RavTrackPCexe.zip or use the .exe file emailed to you from Raveon tech support.
3. Open the .zip archive folder by double-clicking on it. 
4. Locate the directory on your computer that holds the RavTrack PC program. For most users the full path to this file is:  C:/programfiles/raveon/RavTrack PC/
5. Rename the current RavTrack PC.exe file file to RavTrack PCold.exe.
6. Copy the new file from the  named RavTrack PC.exe to your RavTrack PC program directory. For most users the full path to this file is:  C:/programfiles/raveon/RavTrack PC/RavTrack PC.exe

You may now run RavTrack PC as you have been, and the new version will be executed.  If there are data base upgrades to do, RavTrack PC will automatically perform the updates when it starts up.

The M7 GX series of GPS transponders may be directly connected to a Garmin 60C series of hand-held GPSs.  All members of the Garmin 60C family have an RS232 option that is compatible with NMEA 0183 messages.  This allows them to be used with Raveon’s RavTrack series of GPS radio transponders to make a complete GPS tracking system.

When connected to the M7 GPS radio transponder or the Atlas PLPersonal Locator, the Garmin’s map will show the location of all of the the user PLUS the location of all other transponders within radio range.  This unique feature allows one to quickly, easily, and inexpensively, make a portable AVL system for tracking cars, trucks, racecars, construction equipment, or any thing Raveon’s M7 GX or Atlas PL transponder may be installed on.

The Garmin 60C series of hand-held GPSs have built-in interfaces for a “NMEA 0183″ devices, which is another way of saying that they can connect to other devices using a serial cable.   The NMEA 0183 is an RS232 serial connection that typically operates at 4800 baud.  It is used to exchange way-point and other information between displays, GPS devices, and transponders.

When Raveon’s M7 GX transponder is connected to the Garmin display using the NMEA 0183 connection, the GPS radio transponder can put icons on the screen of the Garmin display.  As the transponder receives updated positions from other vehicles, it updates the position of the tracked vehicle icons on the Garmin’s display.

Garmin 60C, 60CS, 60Cx Wiring

From the Garmin technical manual, here is how their NMEA 0183 interface works:

NMEA 0183 Cable Connections

NMEA 0183 is a standard communications format for marine electronic equipment. For example, an autopilot can connect to the NMEA interface on the Garmin 60C and receive positioning information.  The Garmin 60C series can exchange information with any device that transmits or receives NMEA 0183 data.  See the following diagram for general wiring connections. Read yourother product’s owner’s manual for more wiring information.

NMEA 0183 Wiring  (Data cable)

Wiring the Serial Cable

The Garmin’s “Data Cable” must be connected to the M7 GPS transponder (or Atlas OL).  This connection will allow the M7 to put icons on the screen of the Garmin display, showing the location of other tracked vehicles.  The Raveon M7 GPS transponder uses a 9-pin “DB9″ connector to connect to the Garmin.  Solder the Garmin data cable wires onto a DB9 connector and plug the DB9 into the M7 transponder as shown below:

Connect the white wire(serial data from M7 into Garmin) from the Garmin’s Serial Cable goes to pin 2 of the M7’s RS232 DB9 connector.  You do not need to connect the brown wire(serial data from Garmin), so you can trim it off.  Connect the shield braid of the Garmin Serial Cable to pin 5 of the DB9.  The red wire optionally can connect to pin 9 of the Raveon GPS transponder’s DB9 to power the Garmin from the DC source that powers the M7.

If you do not wire your own cable, but instead use Garmin’s RS232 serial cable, you will need to connect the Garmin’s RS232 cable to the M7 GPS transponder using a “NULL Modem” adaptor.

Configuring the Garmin

Set the NMEA communication of the Garmin to 4800 baud.

Configuring the M7 GX Transponder

Raveon has a designed the M7 GX transponder to work with Lowrance Display or any other NMEA 0183 display that can accept the “$GPWPL” NMEA message.   The $GPWPL is an industry standard message that the Lowrance displays and many other GPS displays interpret as a waypoint command.  The M7 GX outputs this $GPWPL message to put icons on the screen of the Lowarance, and to move the icons around on its screen.

To configure the M7 transponder to output the $GPWPL message, set the M7 GX to GPS mode 2.  To do this, put it into the configuration mode by send the +++ into the serial port.  The M7 will respond with an OK.  Type GPS 4 and press enter to put it into GPS 4 mode.  GPS 4 is the mode that causes the M7 GX to output $GPWPL messages whenever it receives a status/position message over the air.

Creating a Map for RavTrack PC

Creating a map to be utilized by RavTrack PC can be completed in just a few steps.  We like to use a powerful mapping program called Global Mapper for development of our maps, however, there are several free programs and websites on the internet that allow you to obtain map images.  For this example, we use a program called Google Map Buddy that was downloaded from CNET.COM.  This blog provides  a short summary of how to obtain a map image, calibrate it with the Ravtrack Software, and then use it with Ravtrack.

                This process will include a quick overview of the program Google Map Buddy.  After which, we will take the image we have obtained and use Ravtrack PC to calibrate the image.  You will need to have Google Earth or a similar program in order to obtain coordinates of your calibration area. 

With Google maps open we begin by opening up Google map buddy:

Enter the exact address of where you want your map centered:

For this example we are centered at the City of Borger Texas:

Select the area that you want the Map to encompass and the zoom level.  Zoom levels go from 1 (low detail) to 19 (high detail) and will increase the file size of your image.   Decide on the level of detail you need and select it from the drop down box.

Click create map and choose a file name:

Google Map Buddy has the option of outputting the image as an aerial satellite view, road (street) map, terrain (Topo) map, or hybrid map.  Select the appropriate option and click OK:

Google Map Buddy will download the image and ask you if you would like to delete the tiles it has downloaded, select yes.

Your image is now created:

The image will be in a PNG file format and will have to now be calibrated to properly represent the latitude and longitude of the points on the map.

Open up Ravtrack PC and select  TOOLS > MAP CREATION TOOL:

Now you will have to open the map PNG image that you created with Google Map Buddy. To do this click MAP > NEW MAP:

The map creation tool will ask you a few questions about the settings. Click OK to the defaults:

Select the images country, Grid, and Datum. The settings illustrated below are correct for the City of Borger .  Click NEXT and proceed:

Select the projection. For smaller images (typically less than 100 miles across) such as the city of Borger, we will use Cartesian. For large land masses, polar would have to be used.  Click NEXT:

Your image will now require the lat/long calibration mentioned earlier.

The tool will ask you to click on a known coordinate (a clear point on the map, such as a road intersection or natural feature).  Before you do this you must be prepared with the precise latitude and longitude of the coordinate you will select:

If you don’t know the lat/long of your coordinate open Google earth and select your location. You will use Google Earth in order to obtain coordinates of 3 points. You will want to choose points towards the periphery of your image. For example, if you have a map of a city, you may select points towards the far upper left, bottom center, and upper right.

Align the map creation tool and Google Earth images side by side, and visually identify an initial coordinate point on each map. This will start the calibration. The calibration consists of finding points on Google earth that correspond to your image’s point on the map. Once you have found that exact map point, copy down the coordinates that are located at the bottom of the Google earth screen.  In the RavTrack PC  screen (the left side screen on the example below) you can now click on the exact location your coordinates correspond to:

The Scaling wizard will come up next. Now you can enter your coordinates. Ensure your coordinates are correct with the proper heading (West, East, North, and south). Click next to finish calibration of this point:

Repeat this step for two more coordinate points and you will receive a scaling complete message. After calibration, save your resulting MAPLIB file to your Ravtrack map directory.  Now you can load your map and use it with Ravtrack!

Here’s a quick list of free programs and websites:

http://download.cnet.com/Google-Map-Buddy/3000-20426_4-10962144.html

http://atlas.ca.gov/imagerySearch.html

http://www.nationalatlas.gov/natlas/Natlasstart.asp

http://www.google.com/mapmaker

http://monarch.tamu.edu/~maps2/

There are many programs and sites that will give you a map image that can be used for calibration.

Overview

Many different types of batteries may be used with Raveon’s M7 series of GPS transponders.  This Technical Brief describes how well some common battery types will work with the M7 radios.

Actual battery life will vary based upon how often the M7 GPS transponder transmits, but the data in this Technical Brief may be used to predict the battery life of most configurations.

Test Setup

For the tests in this brief, a UHF GPS transponder, model RV-M7-UC-GX was configured in GPS mode 2 to transmit its position every 10 seconds.  In GPS mode 2, the radio’s receiver is on 100% of the time, and the current draw of the M7 was an average of 90mA.  The peak current draw was 2.1 amps for 68mS each time the M7 transmitted its GPS position.

Summary Data

Duracell Alkaline

These batteries are the common Duracel batteries found at most department stores.

Test Result Summary

Initial Voltage:                                   12.57 volts

Voltage at ½ discharge:                   10.2 volts

Usable life (hours)                           18 hours

Voltage drop when transmitting       2.4V  (1.1 ohm resistance)

Approximate mAh capacity             1600mAh

Discharge Curve

Transmit Transient

The plot below shows the dip in voltage as the transmitter turns on and off.

Summary

The Duracell is an OK battery to power the M7 transponder.  But its high internal resistance will reduce the RF power output after the first few hours of operation.  The DC to the radio should stay above 9V while transmitting for full power, above 8V for 3-4 watts.

Energizer Lithium

These batteries are the common Energizer Lithium batteries for cameras and digital electronics found at many department stores.

Test Result Summary

Initial Voltage:                                      12.1 volts  (14V for a few moments)

Voltage at ½ discharge:                      12.0 volts

Usable life (hours)                              28 hours

Voltage drop when transmitting          3.5V  (1.6 ohm resistance)

Approximate mAh capacity                2520mAh

Discharge Curve

Transmit Transient

The plot below shows the dip in voltage as the transmitter turns on and off.

Summary

Even though the internal resistance of the cell is higher than the alkaline, the Energizer Lithium is a good battery to power the M7 transponder.  Its high internal resistance will not reduce the RF power output because its voltage is fundamentally fairly high.  The DC to the radio should stay above 9V while transmitting for full power, above 8V for 3-4 watts, so the 3.5V dip means the radio will have full power at 12.5V, and 3-4 watts out at 11V DC at the battery pack.

Lenmar R2G NiMH pack, 2150mAh cells

These batteries are Nickel Metal Hydride rechargeable batteries.  They were fully charged before the test.

Test Result Summary

Initial Voltage:                                      11.0 volts

Voltage at ½ discharge:                      10.3volts

Usable life (hours)                              17 hours

Voltage drop when transmitting          2.0V  (.95 ohm resistance)

Approximate mAh capacity                1500mAh

Discharge Curve

Summary

These batteries should be a good power source for the M7 GX transponder.

The internal cell resistance is low, but the voltage is also low. The RF power output stayed at full power for most of the life of the battery, dropping to about 4 watts at the end of the battery life.  The double dip at end of live was due to the fact the radio keep working down to 6 volts (albeit with almost no RF output because the RF PA is off), and the batteries keep putting our very low voltage for another couple hours.

Raveon Technologies Corporation

990 Park Center Drive, C

Vista, CA 92081

sales@raveontech.com

760-727-8004

TDMA, or Time-Division-Multiple-Access is a very effective way of allowing a lot of radios to share one radio channel.  Used extensively in GSM cellular and APCO public-safety systems, TDMA excels at allowing quick and reliable access to radio channels.  It allows 2-10 times more radios to share a radio channel than conventional carrier-sense methods.  This allows 2-10 times more tracking radios on one channel, as compared to radios that do not have TDMA capability.

The following diagram illustrates how it works.

When a RV-M7 GX wants to report its position and status, it waits until its assigned time-slot, and then transmits its data.  By default, TDMA time slot positions are assigned by unit-ID, so RV-M7 GX with ID 1 uses the first slot, and ID 2 uses the second slot, and so on.  This default slot assignment can be overriden by the SLOTNUM command or by using Raveon’s Radio Manager software, allowing each GX to have an ID that is different than the slot assignment.

A TDMA “Frame” time is the time it takes all units to transmit once.  This is configured with the TDMATIME xx command.  The factory default is 10 seconds, so every 10 seconds, each RV-M7 GX may transmit.  The TDMA frame must be set long enough for all units to transmit.  For example, if you have 50 RV-M7s, and use 200mS TDMA slots, then the TDMATIME should be set to 10 seconds.  The simplest way to set it the TDMATIME is to make it equal to the TXRATE, the rate you wish to report position

The duration of a TDMA time slot is programmed into the RV-M7 GX with the SLOTTIME command. If SLOTTIME is set to 200 milliseconds (factory default), then every 10 seconds, the RV-M7 will have a 200mS window to report its position in.

All TDMA frames are synchronized automatically in all RV-M7 GX Transponders to the top of the minute.  Slot 0, frame 0 is at the top of each minute. They use the internal GPS receiver to determine the current time, and calculate when their are supposed to transmit their position and status information.

A unit may be allocated additional time slots.  The SLOTQTY command sets the number of slots each unit receives.  It is normally set to 1.

After searching for and testing several UHF radios to upgrade a municipal water department’s wireless SCADA system, RAVEON’s Fireline modem was chosen as the best performance/value solution. The simple and versatile ability of the Fireline to be quickly configured easily beat out the other radios on the market. Thirty + radios have been installed and in service continuously operating with no problems for over two years.

Regards.

Chris Carda

President

Criterion Industrial