FIG Peer Review Journal


Evaluation of the TanDEM-X Digital Elevation Model by PPP GPS - Analysis and Intermediate Results (4045)

Juergen Schweitzer, Bimin Zheng, Volker Schwieger and Detlev Kosmann (Germany)
Ms. Bimin Zheng
Scientific Assistant
University of Stuttgart
Geschwister-Scholl Str. 24D
Corresponding author Ms. Bimin Zheng (email: bimin.zheng[at], tel.: + 49 711 68584061)

[ abstract ] [ paper ] [ handouts ]

Published on the web 2010-01-14
Received 2009-11-19 / Accepted 2010-01-14
This paper is one of selection of papers published for the FIG Congress 2010 in Sydney, Australia and has undergone the FIG Peer Review Process.

FIG Congress 2010
ISBN 978-87-90907-87-7 ISSN 2308-3441


From mission TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X) of the German Space Agency (DLR) a global digital elevation model (DEM) will be derived using satellite SAR interferometry. Two radar satellites (TerraSAR-X and Tandem-X) are going to map the earth in such a resolution and accuracy that was not possible in any earlier missions: the aim is an absolute height error of 10m or a relative height error of 2m respectively for 90% of the data. One method to evaluate the accuracy is the use of kinematic Precise Point Positioning (PPP) GPS measurements. The required accuracy is around 0.5 m. The evaluation of the tracks is carried out using the software GIPSY 5.0 of the Jet Propulsion Laboratory (JPL), USA, as well as using the online service of the Natural Resources of Canada named CSRS-PPP. Both results are combined, thus defining the final solution. After the presentation of results for the first track from Munich, Germany, to Sao Martinho, Portugal in 2009, the intermediate results of five tracks located in Europe, China and South America are described and analyzed in this paper. The final average RMS is calculated to 0.49m and the availability rate is determined to 61%. These values justify the characteristics of the first drive and fulfill the requirements. A second focus of the paper is the analysis of the standard deviations provided by the software packages used for this purpose and the processing services respectively. The authors will show that these numerical values are indicators for the actual accuracy, but not in a reliable way. One track in Africa has been processed recently. For the future further tracks should be acquired and processed for India, Russia, North America and Australia.
Keywords: GNSS/GPS; Positioning; Precise Point Positioning; TanDEM-X