Accuracy assessment of the global TanDEM-X Digital Elevation Model with GPS data

Birgit Wessel,Martin Huber,Christian Wohlfart,Ursula Marschalk,Detlev Kosmann,Achim Roth

doi:10.1016/j.isprsjprs.2018.02.017

Birgit Wessel, Martin Huber + Show 4 more

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https://doi.org/10.1016/j.isprsjprs.2018.02.017

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Abstract

The primary goal of the German TanDEM-X mission is the generation of a highly accurate and global Digital Elevation Model (DEM) with global accuracies of at least 10 m absolute height error (linear 90% error). The global TanDEM-X DEM acquired with single-pass SAR interferometry was finished in September 2016. This paper provides a unique accuracy assessment of the final TanDEM-X global DEM using two different GPS point reference data sets, which are distributed across all continents, to fully characterize the absolute height error. Firstly, the absolute vertical accuracy is examined by about three million globally distributed kinematic GPS (KGPS) points derived from 19 KGPS tracks covering a total length of about 66,000 km. Secondly, a comparison is performed with more than 23,000 “GPS on Bench Marks” (GPS-on-BM) points provided by the US National Geodetic Survey (NGS) scattered across 14 different land cover types of the US National Land Cover Data base (NLCD). Both GPS comparisons prove an absolute vertical mean error of TanDEM-X DEM smaller than ±0.20 m, a Root Means Square Error (RMSE) smaller than 1.4 m and an excellent absolute 90% linear height error below 2 m. The RMSE values are sensitive to land cover types. For low vegetation the RMSE is ±1.1 m, whereas it is slightly higher for developed areas (±1.4 m) and for forests (±1.8 m). This validation confirms an outstanding absolute height error at 90% confidence level of the global TanDEM-X DEM outperforming the requirement by a factor of five. Due to its extensive and globally distributed reference data sets, this study is of considerable interests for scientific and commercial applications.

Highlights

Since September 2016 the new TanDEM-X Digital Elevation Model (DEM) can be seen as one of the most consistent, highly accurate and completest global DEM data sets of the Earth surface
The accuracy numbers of the measured TanDEM-X height differnces against kinematic Global Positioning System (GPS) (KGPS) are summarized in Table 3, while Fig. 2a shows the histogram of the height differences which indicates an approximatively uniform distribution around zero
In this study we analyzed the vertical accuracy of the TanDEM-X DEM (0.4” resolution, approx. 12 m) product globally using (a) kinematic GPS data with an accuracy of

Summary

Introduction

Since September 2016 the new TanDEM-X Digital Elevation Model (DEM) can be seen as one of the most consistent, highly accurate and completest global DEM data sets of the Earth surface. This novel product will play a major role in a wide range of various regional and global applications analyzing physical and biological processes of the Earth surface (Zink et al, 2014). The height information was derived by applying single pass Synthetic Aperture Radar (SAR) interferometry. Bi-static interferometry is applied by transmitting pulses from the antenna of only one of the satellites and by receiving the backscattered signals simultaneously with both. SAR interferometry is well suited to globally map the Earth’s surface in a short period of time, due to

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