I have a new dGPS sensor that I’m using with the NXT-G 2.0 Education version. Generally it works well, but I’m having a problem. My project is to drive a small autonomous boat around the waters here in Bahrain (yes, in the Middle East). Besides the dGPS, I have a Mindsensors AGC accel/gyro/compass on another sensor port, and a Mindsensors relay driver on a motor port. The setup has the Mindstorms brick atop the boat in a small waterproof case (see attached photo) with a battery and motors below the case.
The program uses the dGPS navigation block to determine desired heading to a waypoint and the boat navigates there. What I’ve found is that after a few minutes (10+) the reported GPS coordinates become erroneous. They start to “walk off” in a direction different from where the boat really is located. I know this from the log file and from the reported heading that’s clearly in error. I’ve only been able to confirm this behavior on the boat after several minutes of operation,. I haven’t had the time to try to reproduce it (e.g. in my car). I’ve reflashed the NXT brick and there’s no memory space issue even with the log file being written.
Any ideas? Could it be a bad dGPS unit? I purchased it via Amazon two months ago.