Transcript GPS Project Dr. Glen Lightsey - UT Aerospace Engineering

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


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
Single Frequency Code Position Accuracy-GPS Simulation (run1)
-10
-20
-30
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
y-residual
30
25
20
15
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
z-residual
5
0
-5
-10
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
32
30
RSS
Run 1
x-residual
0
28
26
5.1912
5.1912
5.1912
5.1912
Time(sec)
5.1912
5.1912
5.1912
4
x 10
Single Frequency Code Position Accuracy-GPS Simulation (run2)
25
20
15
10
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
y-residual
20
15
10
5
0
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
z-residual
60
40
20
0
-20
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
50
40
RSS
Run 2
x-residual
30
30
20
10
5.1912
5.1912
5.1912
5.1912
5.1912 5.1912
Time(sec)
5.1912
5.1912
5.1912
4
x 10
Single Frequency Code Position Accuracy-GPS Simulation (run3)
20
15
10
5
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
y-residual
25
20
15
10
5
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
z-residual
60
40
20
0
-20
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
50
40
RSS
Run 3
x-residual
25
30
20
5.1912
5.1912
5.1912
5.1912
5.1912 5.1912
Time(sec)
5.1912
5.1912
5.1912
4
x 10
Single Frequency Code Position Accuracy-GPS Simulation (run4)
25
20
15
10
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
y-residual
20
15
10
5
0
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
z-residual
60
40
20
0
-20
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
5.1912
4
x 10
60
50
RSS
Run 4
x-residual
30
40
30
20
5.1912
5.1912
5.1912
5.1912
Time(sec)
5.1912
5.1912
5.1912
4
x 10
Run 1 and Run 2
Single Frequency Code Positioning: PDOP (run1)
Single Frequency Code Positioning: PDOP (run2)
3.2
4
3
3.5
2.8
3
PDOP
PDOP
2.6
2.4
2.5
2.2
2
2
1.8
1.6
5.1912
5.1912
5.1912
5.1912
Time
5.1912
5.1912
5.1912
4
x 10
1.5
5.1912
5.1912
5.1912
5.1912
5.1912
Time
5.1912
5.1912
5.1912
5.1912
4
x 10
Run 3 and Run 4
Single Frequency Code Positioning: PDOP (run4)
Single Frequency Code Positioning: PDOP (run3)
3.6
4
3.4
3.5
3.2
3
PDOP
PDOP
3
2.8
2.6
2.5
2.4
2.2
2
2
1.5
5.1912
5.1912
5.1912
5.1912
5.1912
Time
5.1912
5.1912
5.1912
5.1912
4
x 10
1.8
5.1912
5.1912
5.1912
5.1912
Time
5.1912
5.1912
5.1912
4
x 10
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