GPS Project Dr. Glen Lightsey Investigation of How Accuracy of GPS Measurements is Affected by Errors in the Navigation Data

General Error Sources Space Segment Control Segment User Segment Satellite clock stability Predictability of satellite perturbations Control Segment Ephemeris prediction error Thruster performance User Segment Atmospheric delay (ionospheric, tropospheric) Multipath

Project Error Source Project error from control segment Input error into navigation message Diverge IODE/IODC Four different runs Single satellite/all satellites Data collected

Analysis Performed Used Matlab script to generate: X, Y, Z residuals X, Y, Z mean and standard deviations PDOP The following plots show the results

Run 1

Run 2

  Run 3

Run 4

Run 1 and Run 2

Run 3 and Run 4

Mean and Standard Deviations for all runs   Run 1 Run 2 Run 3 Run 4 XStandard Deviation 2.839260665295466 4.272239014080701 4.406938111010710 3.210611943544223 X Mean Deviation -1.810899195591854 2.238524831074054 1.452102527436283 2.196910571407352 YStandard Deviation 2.081125597206021 2.951748558515313 2.749183333205866 3.271725145171435 Y Mean Deviation 2.109895809803447 1.272517605795222 1.813049299283367 1.244333143827680 ZStandard Deviation 1.535638959253165 1.168424213523795 1.124988085860343 1.363715962099733 Z Mean Deviation -2.532220018706219 8.770300506681473 -4.110255008356439 6.321518295255373

Conclusions In general, run 2 was noisier than most Run 4 was less noisy than either 2 or 3 Runs 2,3,and 4 were noisier than 1 Runs 2 and 3 were not very different The accuracy was degraded by approximately 2 to 5 meters