1 Sat07_73.ppt, 2007-10-23. GPS Definition. Precise satellite navigation-system, which after 1993 will give users a 3-D position and velocity as well as.

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Sat07_73.ppt, 2007-10-23. 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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Sat07_73.ppt, 2007-10-23. GPS

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Sat07_73.ppt, 2007-10-23. GPS

3 SEGMENTS:

Space-segment

Control-segment

User-segment

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Sat07_73.ppt, 2007-10-23. GPS, Configuration

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Sat07_73.ppt, 2007-10-23. 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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Sat07_73.ppt, 2007-10-23. Satellitbaner GPS, i= 550.

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Sat07_73.ppt, 2007-10-23. GPS satellite

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Sat07_73.ppt, 2007-10-23. GPS satellite

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Sat07_73.ppt, 2007-10-23. GPS, Observation principle

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Sat07_73.ppt, 2007-10-23. GPS signal

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Sat07_73.ppt, 2007-10-23. GPS position and velocity determination.

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Sat07_73.ppt, 2007-10-23. GPS signal

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Sat07_73.ppt, 2007-10-23. 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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Sat07_73.ppt, 2007-10-23. Satellite-orbits– orbit changes.

16 parameters,

Updated every

hour

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Sat07_73.ppt, 2007-10-23. 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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CC

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,

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Sat07_73.ppt, 2007-10-23. 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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Sat07_73.ppt, 2007-10-23. GPS, error-sources.

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Sat07_73.ppt, 2007-10-23. Differentiel GPS

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Sat07_73.ppt, 2007-10-23. GPS, position-error.