Mr.RC-CAM
May 03, 2006, 01:01 AM
This is a perhaps a good question for the RCAP community. I continue to see an odd problem with the 201's cross track Steering field flag. It is in the $GPRMB sentence and is the third field; it can be either L or R (steer left or right). On some occasions (it is very intermittent) it will point in the wrong direction. It eventually points correctly, usually after the bearing error becomes larger.
I can see the problem in the demo mode as well as with live data. The LCD display is correct (arrow accurately points to the direction of required travel). Only the NMEA sentence is goofy.
Fortunately, the waypoint destination bearing data is always accurate. So, I've ignored the data field and wrote some steering vector software that cures the problem. However, it is such a weird problem that I would really like to understand what is going on.
Edit: I have come to the conclusion that the steering field is a special flag for use with the XTRAK value, rather than for basic waypoint steering. It's not a big deal to compute the steering vector from the bearing and heading, so I guess there isn't a need to dig any deeper.
I can see the problem in the demo mode as well as with live data. The LCD display is correct (arrow accurately points to the direction of required travel). Only the NMEA sentence is goofy.
Fortunately, the waypoint destination bearing data is always accurate. So, I've ignored the data field and wrote some steering vector software that cures the problem. However, it is such a weird problem that I would really like to understand what is going on.
Edit: I have come to the conclusion that the steering field is a special flag for use with the XTRAK value, rather than for basic waypoint steering. It's not a big deal to compute the steering vector from the bearing and heading, so I guess there isn't a need to dig any deeper.