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

2. 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

3. 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

4. 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

5. Run 1

6. Run 2

7. Run 3

8. Run 4

9. Run 1 and Run 2

10. Run 3 and Run 4

11. Mean and Standard Deviations for all runs
Run 1
Run 2
Run 3
Run 4
XStandard Deviation
X Mean Deviation
YStandard Deviation
Y Mean Deviation
ZStandard Deviation
Z Mean Deviation

12. 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