GPS Project Dr. Glen Lightsey - UT Aerospace Engineering
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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