1 Sat05_73.ppt, 2005-12-05. GPS Definition. Precise satellite navigation-system, which after 1993...
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Transcript of 1 Sat05_73.ppt, 2005-12-05. GPS Definition. Precise satellite navigation-system, which after 1993...
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Sat05_73.ppt, 2005-12-05. GPS Definition.
Precise satellite navigation-system,
which after 1993 will give users a 3-D position and velocity as well as a precise time
anywhere on and in the vicinity of the Earth
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Sat05_73.ppt, 2005-12-05. GPS
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Sat05_73.ppt, 2005-12-05. GPS
3 SEGMENTS:
Space-segment
Control-segment
User-segment
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Sat05_73.ppt, 2005-12-05. GPS, Configuration
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Sat05_73.ppt, 2005-12-05. GPS Constallation
18 satellites and 4 reserve in 6 planes
Lifetime: 7.5 years
6 planes, 600 separated
Inclination: 550
Semimajor axis: 26000 km
Period: 11 hours 58 min
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Sat05_73.ppt, 2005-12-05. Satellitbaner GPS, i= 550.
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Sat05_73.ppt, 2005-12-05. GPS satellite
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Sat05_73.ppt, 2005-12-05. GPS satellite
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Sat05_73.ppt, 2005-12-05. GPS, Observation principle
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Sat05_73.ppt, 2005-12-05. GPS signal
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Sat05_73.ppt, 2005-12-05. GPS position and velocity determination.
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Sat05_73.ppt, 2005-12-05. GPS signal
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Sat05_73.ppt, 2005-12-05. GPS Signal (II)
L1: 154 x 10.23 MHz = 1.57542 GHz
L2: 120 x 10.23 MHz = 1.22760 GPz
Whar is the wave-length ?
Modulated with P-Code: 10.23 MHz = ca. 30 m,
Repeated after 266 days = 7 days for 1 satellite
Zero at 0.0 UT Saturday/sunday
Only L1 modulated with C/A code: 1.023 MHz =
Ca. 300 m
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Sat05_73.ppt, 2005-12-05. Satellite-orbits– orbit changes.
16 parameters,
Updated every
hour
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Sat05_73.ppt, 2005-12-05. Satellite orbit parameters for GPS
• Mean-anomali
• Mean-anomaly change
• Excentricity
• Square-root semimajor axis
• Rectacensionen
• Inclination at t0e
• Perigæums argument
• Tidsændring af rectac.
• Time-change of i
• Corection of f+
• Correction of r
• Reference-time
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Sat05_73.ppt, 2005-12-05. Satellite orbit error - relative positioning
Influence of orbit-error
on position determination
Reduced if we determine
difference-vector
Relativ precision:
db/b dr (m) b(km) db
1 ppm 20 10 1cm
0.1 ppm 2 10 0.1
100 1
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Sat05_73.ppt, 2005-12-05. GPS, error-sources.
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Sat05_73.ppt, 2005-12-05. Differentiel GPS
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Sat05_73.ppt, 2005-12-05. GPS, position-error.