NMEA Converstion from Garmin USB Protocol

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NMEA Converstion from Garmin USB Protocol

Stephen Wayne Stanaland

Hi Everyone,

This is my first email on the GPSBabel email list. I have an application that reads all the NMEA streams from the serial output of a GPS via a COM port. I am now looking to utilize the Garmin USB protocol for the same effect.

Using the program, "GPSGate", I am able to convert the Garmin USB protocol to a NMEA stream and push it to a COM port. This does everything I need it to EXCEPT publish $GPRMB data.

I have been working on my own Garmin reader and am accurately receiving the PVT data. The idea is to build my own NMEA converter or just push the data directly to my application. I have been using GPS Babel to see the capabilities of the Garmin devices (their information seems pretty limited). I can gather all the waypoints, but not error correction data.

Is it possible to retrieve all the information to accurately build a $GPRMB string given only the data from the Garmin USB? If so, how would I get started?



Here is an example RMB string:

Example GPRMB message.


RMB     Recommended Minimum Navigation Information



1 2  3   6      7 8       9 10 11 12 13|

| |  |   |      | |       | |  |  |  | |



1) Status, V = Navigation receiver warning

2) Cross Track error - nautical miles

3) Direction to Steer, Left or Right

4) TO Waypoint ID

5) FROM Waypoint ID

6) Destination Waypoint Latitude

7) N or S

8) Destination Waypoint Longitude

9) E or W

10) Range to destination in nautical miles

11) Bearing to destination in degrees True

12) Destination closing velocity in knots

13) Arrival Status, A = Arrival Circle Entered

14) Checksum

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