Overview
Over-the-air position/status messages that the M7 GX transceiver and the Personal Locator may receive are sent out the serial port using Raveon’s proprietary message format called the $PRAVE message. The $PRAVE message is used to pass the tracked vehcile’s ID, location, speed, and status. The $PRAVE message format is the default message format when the unit is configured for GPS mode 2.
Structured like a standard NMEA GPS message, the $PRAVE message contains a rich set of location and status information. The $PRAVE message is sent out the serial port of the radio, each time the radio receives a position message over-the-air.
Please note, the $PRAVE message is not transmitted over-the-air. Raveon transmits over-the-air a highly compressed form of the data held in the $PRAVE message. When an M7 GX receives this over-the-air position/status report, the received information is decompressed and the data is sent out the serial port, in one of a number different formats. One of these formats is this $PRAVE message. Other options are the NMEA $GPWPL message and the $GPTLL message. These are covered in the user manual for the M7 GX radio transponder.
$PRAVE Message Format
The $PRAVE message is sent out the RV-M7 GX when it is configured for GPS 2 mode of operation. This mode is typically used with the RavTrack PC program, or other computer programs that can process position and status information. GPS mode 2 instructs that the output be sent at 38.4K bytes/second out the serial port.
Along with ID and position information, the $PRAVE contains a host of other status information. The length of this message may exceed he standard NMEA limit of 79 characters. Any product or software that uses this message must take this into account.
Following is a list of the fields sent in this message
|
Field |
Usage |
Comments |
|
1 |
$PRAVE |
Raveon Proprietary Header |
|
2 |
From ID |
The ID of the transponder that transmitted its position over the air. It is a decimal number, 0 – 9999. |
|
3 |
To ID |
The ID that this position report was sent to. It is a decimal number, 0 – 9999. |
|
4 |
Latitude |
dddmm.mmmm format. It is signed. + is north, – is south. No sign means north. Note: typically there are 4 decimal places, but as few as 0 decimal places are possible. Null field if no GPS lock. |
|
5 |
Longitude |
dddmm.mmmm format. It is signed. + is east, – is west. No sign means east. Note: typically there are 4 decimal places, but as few as 0 decimal places are possible. Null field if no GPS lock. |
|
6 |
UTC time |
The UTC time at the time the transmission was made. Hhmmss format. Null field if no GPS lock. |
|
7 |
GPS Status |
0=not valid position. > 0 is valid GPS. 1=GPS locked and valid position, 2=GPS locked with WAAS corrections applied |
|
8 |
Num Satellites |
The number of satellites in view |
|
9 |
Altitude |
The altitude in meters. Null field if no GPS lock. |
|
10 |
Temperature |
The internal temperature of the RV-M7 in degrees C. Typically this is 5-20 degrees above ambient. |
|
11 |
Voltage |
Input voltage to the device that sent this position. |
|
12 |
IO status |
A decimal number representing the binary inputs. |
|
13 |
RSSI |
The signal-strength of this message as measured by the receiver, in dBm. Note, if the message went through a repeater, it is the signal lever of the repeated message. |
|
14 |
Speed |
The speed of the device in km/hour, 0-255 |
|
15 |
Heading |
The heading of the device 0-360 degrees. |
|
16 |
Alerts |
Alert codes for alerts currently indicated in the device. NULL means no alerts. “P” means a proximity alert. “A”means alert. “C” means critical alert, “M” means man-down. |
|
17 |
Spare |
A spare field. May be used for UTC date in the future. Typically NULL. |
|
18 |
* |
The “*” NMEA end-of-message identifier. |
|
19 |
Checksum |
The NMEA 0183 checksum. |
Example Sentence:
$PRAVE,0001,0001,3308.9051,-11713.1164,195348,1,10,168,31,13.3,3,-83,0,0,,*66
This example shows a unit at 33° 8.9051 north latitude and 117° 13.1164 east longitude. It is not moving (0 speed). Its signal strength was -83dBm. Its altitude is 168 meters.
For your curiosity or testing purposes, below is a capture of vehicle 0003 driving around the Raveon office in Vista, California.
$PRAVE,0003,0001,3308.9077,-11713.1259,154656,1,8,200,24,11.6,0,-69,0,0,,*76
$PRAVE,0003,0001,3308.9082,-11713.1262,154716,2,8,199,24,11.6,0,-64,0,0,,*7C
$PRAVE,0003,0001,3308.9084,-11713.1267,154736,2,8,198,24,11.6,0,-64,0,0,,*7C
$PRAVE,0003,0001,3308.9092,-11713.1288,154756,2,9,198,24,11.6,0,-61,4,-298,,*52
$PRAVE,0003,0001,3308.9225,-11713.1239,154816,2,8,195,25,11.6,0,-62,8,-18,,*65
$PRAVE,0003,0001,3308.9418,-11713.1146,154836,2,9,190,26,11.6,0,-85,3,-14,,*6D
$PRAVE,0003,0001,3308.9532,-11713.1314,154842,2,9,186,26,11.6,0,-96,38,-294,,*65
$PRAVE,0003,0001,3308.9654,-11713.1665,154846,2,9,182,26,11.6,0,-102,61,-292,,*53
$PRAVE,0003,0001,3308.8880,-11713.1500,155010,2,9,179,29,11.6,0,-86,19,-40,,*5B
$PRAVE,0003,0001,3308.9120,-11713.1327,155030,2,9,183,30,11.6,0,-72,1,-206,,*57
$PRAVE,0003,0001,3308.9116,-11713.1304,155050,2,9,191,31,11.6,0,-71,0,0,,*7C