The TanDEM-X PolarDEM is a framework for the provision of derivatives of the global Digital Elevation Model (DEM) of the TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) mission. The global TanDEM-X DEM is a consistent data set with unprecedented accuracy. It was compiled from interferometric SAR data sets acquired between 2010 and 2014. The resulting global TanDEM-X DEM still faces some limitations that shall be tuned in the turn of this project, specifically for Polar Regions. The derivatives produced in TanDEM-X PolarDEM include edited DEM products, single year coverages and penetration bias corrected DEMs of Polar Regions.
The editing comprises
TanDEM-X PolarDEM 90 Products
The goal of the TanDEM-X PolarDEM 90 products is to produce an edited and gap-free version of the TanDEM-X global DEM in Polar Stereographic projection, a metric coordinate system with homogeneous pixel spacing of 90 meters.
The production steps comprised the following steps
Time Tagged TanDEM-X PolarDEM 90
The global DEM of the TanDEM-X mission is a compilation of several acquisition campaigns performed at different years and with different imaging conditions. Usually, the consideration of such multiple acquisitions increases the accuracy of the resulting DEM. An average height resulting from different acquisitions describes well the shape of a glacier or an ice shield but does not reflect the real situation of any of the single acquisition dates. The use of such a DEM e.g. for ice mass balances is limited.
The purpose of the Time Tagged TanDEM-X PolarDEM 90 is to provide the state for a single winter season to broaden the applicability of the elevation models. The calibration and mosaicking is performed in the original product spacing in geographic coordinates. The Time Tagged TanDEM-X PolarDEM is finally transformed into a cartographic system with a homogeneous metric spacing of 90 meters in northing and easting. An editing process is not applied.
In addition, SAR signals are usually not reflected directly on the surface of a glacier. They penetrate into the snow and ice surface which leads to a bias in the measured height. This height bias is dependent on the radar frequency, the imaging conditions like incidence angle and interferometric baseline length, and the physical and dielectric characteristics of the snow and ice layer. This limitation should be considered in a revised version of the Time Tagged TanDEM-X PolarDEM.
For further information, please consult the PolarDEM Product Description (see Downloads).
Status and availability:
Duration: 2017 – ongoing
The photo from Antarctica was kindly provided by Dr. Dana Floricioiu, DLR-IMF