# Presentation: 491021

## CGSIG  MEETING

**CGSIG  MEETING**

**PRAGUE.1999**

## POSSIBILTIES  &  LIMITATIONS

- DIFFERENTIAL  GPS

## PRECISION  AND ACCURACY

***PRECISION  AND ACCURACY***
*** ******PRECISION OF GPS***
***ACCURACY OF GPS***

## ρ = c .τ

***ρ = c .τ***
***Δρ = c . Δτ***
***Δρ = 3.10******8 ******m/s . 10****** -12 ******s***
***Δρ = 0.3 mm***

***PRECISION OF THE GPS SYSTEM***

## Tipical satellite path without S/A

- 6om

***Tipical satellite path without S/A***

- 0

- 11:54

**U**

**U= User equivalent range error**

## ACCURACY OF THE GPS SYSTEM

***SPS USER EQUIVALENT ERROR [m]***

***ACCURACY OF THE GPS SYSTEM***

**SA                AS                 C/A             RT MAX**

**YES**
**NO**
**YES**
**NO**

**YES**
**YES**
**NO**
**NO**

**100(150)**
**40(60)**
**100(150)**
**40(60)**

**300(450)**
**120(180)**
**300(450)**
**40(60)**

## Tipical satellite path with S/A

- 1oom

***Tipical satellite path with S/A***

- 0

- 11:54

**U= User equivalent range error**

**U**

## Slide 8

## Postioning accuracy vs Observation time

**1min**

**1****0min**

**1hour**

**12hours**

**1day**

**100**

**300**

**Pos. error**

**Obs. time**

**1m**

**3m**

**Postioning accuracy vs Observation time**

## RTCM

**3min**

**0**

- PRC

- RRC

**RTCM**
**SC 104**
**Ver 2.0**

## POSITONING COST vs ACCURACY

**COST**

**ACCURACY 1σ**

- 100m

- 10m

- 1m

- 10cm

- 1cm

- 1mm

- 0.3mm

**POSITONING COST vs ACCURACY**

## POSITONING COST vs ACCURACY

**Demand**

**ACCURACY 1σ**

- 100m

- 10m

- 1m

- 10cm

- 1cm

- 1mm

- 0.3mm

**POSITONING COST vs ACCURACY**

**DGPS**

**RTK**

**POSTPROCESSING**

## Slide 13

## DGPS Corrections I.

- C/A  code

- PRCi = ρ’i -| ***r*** - ***R*** |i
-  RRCi = PRCi - PRCi-1

- ρi = | ***r*** - ***R*** |i  +  PRCi
- ρi = ρi-1 + RRCi-1

- RTCM v2.0

- True range

**PRC : Pseudorange correction**
**RRC: Range rate correction**
**r : satellite position**
**R : reference position**
**ρ’ : pseudorange**
**ρ : corrected range**

**BASE**

**REC**

## DGPS Corrections II.

- Carrier phase

- CFCi = Φ**’****i** - **FRAC(** ρi /(N*λ))
- N = INT (ρi / λ)
- DFCi = CFCi - CFCi-1

- Φi = Φ**’****i**  +  CFCi
-    Φi = Φi -1 + RFCi -1

- RTCM v2.1

- True phase

**CFC : Carrier Phase Correction**
**RPC: Rate of Phase Correction**
**N : resolved ambiguity**
- Φ**’ : raw phase**
**ρ : corrected range**
- Φ : **correct phase**

**BASE**

**REC**

## Slide 16

## Geostationary satellite                Terrestrial radio

**	****   ****	****           ****	****            ****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**

## Slide 18

## FM BROADCASTING SITES