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CGSIG MEETING

CGSIG MEETING. PRAGUE.1999. DIFFERENTIAL GPS. POSSIBILTIES & LIMITATIONS. PRECISION AND ACCURACY PRECISION OF GPS ACCURACY OF GPS. PRECISION OF THE GPS SYSTEM. ρ = c .τ Δρ = c . Δτ Δρ = 3.10 8 m/s . 10 -12 s Δρ = 0.3 mm. Tipical satellite path without S/A. U. 6om. 0. 11:54.

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CGSIG MEETING

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  1. CGSIG MEETING PRAGUE.1999

  2. DIFFERENTIAL GPS POSSIBILTIES & LIMITATIONS

  3. PRECISION AND ACCURACY • PRECISION OF GPS • ACCURACY OF GPS

  4. PRECISION OF THE GPS SYSTEM ρ = c .τ Δρ = c . Δτ Δρ = 3.108 m/s . 10 -12 s Δρ = 0.3 mm

  5. Tipical satellite path without S/A U 6om 0 11:54 U= User equivalent range error

  6. ACCURACY OF THE GPS SYSTEM SPS USER EQUIVALENT ERROR [m] SA AS C/A RT MAX YES YES NO NO YES NO YES NO 100(150) 40(60) 100(150) 40(60) 300(450) 120(180) 300(450) 40(60)

  7. Tipical satellite path with S/A U 1oom 0 11:54 U= User equivalent range error

  8. Postioning accuracy vs Observation time Pos. error 300 3m 100 1m Obs. time 1min 10min 12hours 1day 1hour

  9. RTCM SC 104 Ver 2.0 RRC PRC 0 3min

  10. POSITONING COST vs ACCURACY COST ACCURACY 1σ 100m 1mm 10m 1m 10cm 1cm 0.3mm

  11. POSITONING COST vs ACCURACY Demand DGPS RTK POSTPROCESSING ACCURACY 1σ 100m 1mm 10m 1m 10cm 1cm 0.3mm

  12. DGPS Corrections I. C/A code PRCi = ρ’i -| r - R |i RRCi = PRCi - PRCi-1 BASE RTCM v2.0 ρi = | r - R |i + PRCi ρi = ρi-1 + RRCi-1 True range REC PRC : Pseudorange correction RRC: Range rate correction r : satellite position R : reference position ρ’ : pseudorange ρ : corrected range

  13. DGPS Corrections II. Carrier phase CFCi = Φ’i - FRAC(ρi /(N*λ)) N = INT (ρi / λ) DFCi = CFCi - CFCi-1 RTCM v2.1 BASE True phase Φi = Φ’i + CFCi Φi = Φi -1 + RFCi -1 REC CFC : Carrier Phase Correction RPC: Rate of Phase Correction N : resolved ambiguity Φ’ : raw phase ρ : corrected range Φ : correct phase

  14. DIFFERENTIAL CORRECTIONS • for • REALTIME PRECISE NAVIGATION • Geostationary satellite Terrestrial radio • Wide area coverage Contry to continental • Availabilty in high seas Availabilty in urbanareas • Accuracy 5 - 10 m Accuracy submeter • Latency  6 sec Latency  0.1 sec • Low elevation Topographic warmholes • Expensive antenna Inexpensive antenna • Sophisticated receiver Simple pager receiver

  15. FM Multiplex signal spectrum Deviation (%) 75 50 0 19 5776 Frequency (KHz)

  16. FM BROADCASTING SITES

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