The Larry Project

4/3/2005

gps coordinates

Filed under: Senior Project — von der Lord Larry @ 11:18 pm

I spent 6 hours today trying to fix the problem with the coordinate system. I tried a few different things. I tried scaling the output to match the scale of the velocity output, but the scale factor was dependent on the direction of travel and was useless. I verified that the lat/long numbers were being read and converted properly. I put in a different set of expressions to change from lat/long/alt to ECEF with no results. I have looked over the rotation matrix for the ECEF-SEZ transformation. It looks ok. Currently the East coordinate is being calculated correctly, but the South coordinate is off by a factor that ranges from 3.16 to 3.5 or so. I need to output the ECEF coordinates and verify them by taking a series of measurements over time at a constant simulated velocity. Then find the magnitude of the change in position. I will take this distance divided by time and compare with the magnitude of the velocity reported by the GPS. If they Are the same, I will be fairly certain that the lat/long to ECEF conversion is OK. Then I will verify all of the intermediate calculations and the transformation matrix to SEZ.

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