Hi guys,
there is a commentary in the MAVLink protocol that describes some important gps parameters:
* @param lat Latitude in 1E7 degrees
* @param lon Longitude in 1E7 degrees
* @param alt Altitude in 1E3 meters (millimeters) above MSL
* @param eph GPS HDOP horizontal dilution of position in cm (m*100). If unknown, set to: 65535
* @param epv GPS VDOP horizontal dilution of position in cm (m*100). If unknown, set to: 65535
* @param vel GPS ground speed (m/s * 100). If unknown, set to: 65535
* @param cog Course over ground (NOT heading, but direction of movement) in degrees * 100, 0.0..359.99 degrees. If unknown, set to: 65535
* @param satellites_visible Number of satellites visible. If unknown, set to 255
I sorted my ArduPilot log in a excel file in a way that I can compare the values that are labeled with "groundspeed" with the one that are labeled "vel". The results are that on the one hand there are a lot more values for "groundspeed" than vor "vel" and on the otherhand these values are mostly not coincidence.
Does anybody know what this means or what the parameter "vel" is for?
Thanks and greets!
Martin
Replies
Hi,
Well the value really is just the GPS ground speed. You can see that in the file GCS_MAVLink.pde in ArduPlane in the ardupilot sources. Find the send_gps_raw procedure. It is OK readable even if you don't program computers.
You get more groundspeed values because this name is used for the same value in a different message, the vfr_hud message. That message gets sent more often. The 2 messages have different purposes but both purposes need a ground speed.
Regards
Soren