The standard M7-GX GPS tracking transponder has 2 separate reporting rates, the TXRATE and the IDLERATE. In many deployments the TXRATE and IDLERATE are identical. However, in some deployments the IDLERATE is set to transmit position less frequently than the TXRATE unless a specified event occurs.
Some of these events include:
Speed of travel greater than a user specified value (TRIGSPEED parameter)
Distance of travel greater than a user specified value (TRIGDX parameter)
Proximity to another GX transponder less than a user specified value (PROX parameter).
Here are three examples of using this flexibility in your system.
Example – Using TRIGSPEED
Picture a police squad car sitting idle or cruising slowly through a neighborhood on patrol. In this instance it may not be important for the vehicle to transmit a position report more frequently than every 2 minutes. If this is the case IDLERATE can be set for 120 (seconds). However, the same squad car may later be move at higher speeds and reporting more frequently becomes important . In our example the system administrator has set the fastest reporting frequency at 10 seconds (TXRATE 10). When the car speed exceeds a certain threshold, let’s say 40kph (TRIGSPEED 40) the TXRATE is invoked and reports are now sent every 10 seconds. When the car slows down, the IDLERATE again takes over, and transmissions are less frequent.
Example – Using TRIGDX
Your public works department has a number of vehicles out every day serving the community. A vehicle and crew may stop for a while and work at a particular site. While at the site they may even move the vehicle around a bit, to aid in the work. While on the site a position report rate frequency of 5 minute intervals is perfectly adequate. However, when they pick up and start moving to a new site, you’d like to be able to track their progress and know where they are more frequently, once they’ve moved 100 feet or so. In this case your maximum system reporting frequency is twice a minute , or TXRATE 30 (seconds) Set IDLERATE 300 (seconds), and TRIGDX 30 (meters). 30 meters is roughly 100 feet.
You drive aheavy equipment in an open pit mine, or on a construction site. The visibililty from your cab isn’t all that great, and you drive and operate your equipment as carefully as possible at all times. In a move to further improve safety your company has placed a tracking display in your vehicle, allowing you to display the location of all of your other RavTrack transponders within radio range. Your system administrator has set the following parameters in all of your transponders:
IDLRATE 10 (seconds)
TXRATE 2 (seconds)
PROX 15 (meters)
During your normal activities the display in your vehicle updates the location of all other transponders every 10 seconds. Somewhere along the line, one of your coworkers, while on foot, comes close to your equipment. Your co-worker (Jim) is wearing on his belt the ATLAS PL personal locator. When he gets within 50 feet of you (about 15 meters) your transponder, which was transmitting at 10 second intervals, starts transmitting positions ever 2 seconds – and so does his ATLAS PL unit. Now the blip on your display that represents your Jim starts pulsing every 2 seconds, perhaps a light has also lit on your dashboard, or a buzzer sounds in your cab, alerting you to Jim’s nearby presence.
We will cover the integration of warning lights and buzzers in another tech blog.
For the more technically minded, here is the logic flow chart the GPS transponder tests internally every TXRATE.