Quality Assessment of the TanDEM-X Global Digital Elevation Model

Abstract

TanDEM-X is an innovative synthetic aperture radar (SAR) mission with the main goal to generate a global and homogeneous digital elevation model (DEM) of the Earth’s land masses. The final DEM product will reach a new dimension of detail with respect to resolution and quality. The absolute horizontal and vertical accuracy shall each be less than 10 m in a 90% confidence interval at a pixel spacing of 12 m. The vertical height specification for the TanDEM-X mission foresees a 90% point-to-point error of 2 m (4 m) for areas with predominant terrain slopes smaller than 20% (greater than 20%) within a 1° longitude by 1° latitude cell. The global DEM is derived from interferometric SAR acquisitions performed by two radar satellites flying in close orbit formation at distances of around 500 m. Interferometric performance parameters like the coherence between the two radar images per acquired scene have been monitored and evaluated throughout the mission. The paper will discuss the derived quality statistics and present global performance maps. The TanDEM-X mission concept foresees multiple coverages of the land masses which will be acquired by end of 2014. In a further step, the over 500,000 single SAR scenes are interferometrically processed, calibrated, and mosaicked into a global DEM product. By end of 2014, about 40% of the global DEM will be available with the full delivery expected early 2016. This paper will present first quality examples of the final DEM product in terms of relative and absolute height accuracy.