# Presentation: 865385

## Progress of the real-time GNSS software development at GFZ

**Junping Chen**, Maorong Ge, Markus Vennebusch,
- Zhiguo Deng,Gerd Gendt, Markus Rothacher
- Department of Geodesy and Remote Sensing,
-  GeoForschungsZentrum, Postdam
- Contact:  junping.chen@gfz-potsdam.de
- IGS Workshop 2008
- Miami Beach, Florida, USA
- 2-6 June, 2008

- IGS Workshop 2008,4 June,2008

##  Content

**Prototype software**
**Real-time investigations**
- Orbit influence
- Network influence
- Tropospheric parameter estimation
**Real-time implementation**
- Satellite clock estimation
- Kinematic PPP solution
- Network solution
**Conclusions**

*** ******Content***

- IGS Workshop 2008,4 June,2008

## Background

**GFZ real-time activities**
**Hardware development**
**Data streaming (21 stations)**
**Real-time software development**
- providing satellite orbits and clocks in real-time
- kinematic monitoring of station positions in real-time
**different procedures**
- PPP mode (satellite orbit/clock estimation, PPP for single station)
- Network mode** **(station coordinates)
**G-SEIS(GPS - SurfacE Deformations withIn Seconds** **)**
**IGS-RT pilot project**
**Details in Poster:**
- M. Vennebusch, M. Ramatschi, J. Chen, C. Falck, M. Ge, Th. Nischan, M.Rothacher
**Real-time GNSS activities at GeoForschungsZentrum Potsdam**

- IGS Workshop 2008,4 June,2008

## Structure of GFZ prototype system

**Strategies**
**        ****Clock estimation: **epoch-wise differences
**        ****Estimator: **Square Root Information Filter
**Parameters**
**        **Sat. orbits & clocks; station coordinates & clocks, troposphere;ambiguities

- Processing kernel

**Wuhan University,China** is
- acknowledged for providing
- PANDA software as the basis of our current processing kernel.

- USER

- GFZ

- IGS Workshop 2008,4 June,2008

## Simulated real-time investigations

**        ****data** **streaming based on daily rinex file, Doy 318,2007, sampling:30 sec**
**Orbit influence**
- Clock estimation using different orbits
- Kinematic coordinates using different orbit & clock
**Network influence**
- Clock estimation from different networks
- Kinematic coordinates using different clock (from different network)
**Tropospheric parameter estimation**

***Simulated real-time investigations***

- IGS Workshop 2008,4 June,2008

## Orbit influence: clock estimation

**Selected network (IGR network as processed by GFZ,75 stations)**

***Orbit influence: clock estimation***

**Std.=0.14ns**

**IGS orbits: Std. =0.11ns**

**Prediction**

**Prediction**

**Orbit prediction:** less than 6 hours is recommended.

- For satellites without manoeuvre

**Std.=0.12ns**

**Clock differences compared to IGS final clock**

- IGS Workshop 2008,4 June,2008

## Orbit influence: kinematic PPP

**A: IGS orbit, clock estimated from IGS orbits ****(consistent)**
**B: IGS orbit, clock estimated from IGU_00 orbits****(inconsistent)**
**C: IGU_00 orbit, clock estimated from IGU_00 orbits****(consistent)**

| Africa | N-S(cm) | E-W(cm) | H(cm) |
| --- | --- | --- | --- |
| A | 2.41 | 4.16 | 11.96 |
| C | 2.71 | 4.32 | 12.55 |
| B | 3.21 | 5.31 | 13.04 |

| Australia | N-S(cm) | E-W(cm) | H(cm) |
| --- | --- | --- | --- |
| A | 1.71 | 3.56 | 8.19 |
| C | 1.94 | 3.83 | 9.23 |
| B | 2.47 | 4.59 | 8.08 |

**RMS of kinematic coordinates (compared to IGS weekly solution)**

**Similar precision, using consistent orbits and clocks. **
**Precision degraded, inconsistent orbits and clocks.**
**Regions with better station distribution, better results.**

| Africa | N-S(cm) | E-W(cm) | H(cm) |
| --- | --- | --- | --- |
| A | 2.41 | 4.16 | 11.96 |
| C | 2.71 | 4.32 | 12.55 |
|  |  |  |  |

| Australia | N-S(cm) | E-W(cm) | H(cm) |
| --- | --- | --- | --- |
| A | 1.71 | 3.56 | 8.19 |
| C | 1.94 | 3.83 | 9.23 |
|  |  |  |  |

- IGS Workshop 2008,4 June,2008

## Network influence: clock estimation 

**Different networks**

**IGR network **
**(as processed by GFZ)**

**Real-time network**

**Clock estimation (based on IGU_00 orbit, 24 h prediction)**

**Satellite clock precision degraded in real-time!**

**Std.=0.33ns**

**Std.=0.19ns**

- IGS Workshop 2008,4 June,2008

## Network influence: kinematic PPP 

***Network influence: kinematic PPP***

| Africa | N-S(cm) | E-W(cm) | H(cm) |
| --- | --- | --- | --- |
| Real-time | 5.34 | 8.54 | 13.42 |
| IGR | 2.71 | 4.32 | 12.55 |

| Australia | N-S(cm) | E-W(cm) | H(cm) |
| --- | --- | --- | --- |
| Real-time | 3.08 | 4.74 | 8.37 |
| IGR | 1.94 | 3.83 | 9.23 |

**RMS (horizontal) using real-time is almost ****twice ****as the solution using IGR network.**

**RMS of kinematic coordinates (compared to IGS weekly solution)**
**IGU_00 orbit, clock estimated from different networks (based on IGU_00 orbits)**

- IGS Workshop 2008,4 June,2008

## Troposphere estimation 

**Correlation between Trop. and station height (Station: TALA)**
-    Coef.= -0.6

***Troposphere estimation***

**New strategies are needed to be implemented in epoch-wise estimation!**

- IGS Workshop 2008,4 June,2008

## Real-time implementation 

**Satellite Clock estimation**
**Data: **real-time network(2008,May,8), 52 real-time stations
**Orbit: **IGU_00
**Parameters: **
-        	Station clocks; troposphere, satellite clocks, ambiguities
**Processing time: **~0.2s CPUT per epoch on IBM T60
**Kinematic PPP solution**
**Data: **real-time data streaming(2008,May,8)** **
**Orbit: **IGU_00
**Clock: **real-time clock
**Network solution**
**Data: **real-time data streaming (European network,2008,Feb.,1),30 stations** **
**Orbit: **IGU_00
**Parameters:**
-          	station coordinates & clocks; troposphere; satellite clocks; ambiguities

- IGS Workshop 2008,4 June,2008

## Real-time: Satellite clock & kinematic PPP

**Clock estimation (compared to IGS AC’s clock)**

***Real-time:*** ***Satellite clock & kinematic PPP***

| mean (ns) | Std. (ns) |
| --- | --- |
| -0.05 | 0.36 |

**Coordinates (compared to IGS weekly solution)**

**Similar clock and PPP precision as in investigation.**
**Clock jumps due to data problems.**
**Coordinate jumps occur at the same epoch.**

|  | N-S(cm) | E-W(cm) | H(cm) |
| --- | --- | --- | --- |
| Bias | 0.6 | 1.6 | 1.6 |
| Std. | 2.2 | 3.9 | 5.5 |

- IGS Workshop 2008,4 June,2008

## Real-time: Network solution

***Real-time:*** ***Network solution***

**Network:**
-   Real-time GNSS Data Stream in Europe.
-   30 stations were processed (15 station fixed,12 as static, 3 as kinematic);

|  | X(cm) | Y(cm) | Z(cm) |
| --- | --- | --- | --- |
| Bias | 2.2 | 1.2 | -2.3 |
| Std. | 2.0 | 1.1 | 1.3 |

- IGS Workshop 2008,4 June,2008

##  Conclusions

**Simulated real-time investigation****	**
- Satellite clock precision (using IGR network): ~0.1ns
- Orbit update: less than 6 hours is recommended.
- Regions with a good station distribution achieve better results in PPP.
- Network: Stations in Africa, Asia and South America are needed to be updated to real-time (21 GFZ real-time stations implemented already!).
**Performance of prototype software (in real-time)**
- Satellite clock estimation precision : ~0.3ns
- Kinematic coordinate precision (PPP): <10 cm
- Network solution precision : <3 cm
**Further works**
- Preprocessing strategy
- Troposphere estimation strategy
- Filter initialization
- Products services

- IGS Workshop 2008,4 June,2008

## Thank you!

- IGS Workshop 2008,4 June,2008