The TanDEM-X DEM Change Maps is a project developed by the Institute Remote Sensing Technology (IMF) at the German Aerospace Center (DLR) within the activities of the TanDEM-X Mission. Between 2016 and 2022, the TanDEM-X mission acquired an additional complete coverage of the Earth's landmass to deliver a temporally independent coverage within a well-defined time span. These new acquisitions not only provide more up-to-date elevation information, but also a great dataset to show the changes that have occurred during the years separating this new coverage from the coverages acquired to generate the TanDEM-X global DEM (between 2011 and 2014). This product - the TanDEM-X 30 m DEM Change Maps - shows the changes between the edited first global TanDEM-X DEM (TanDEM-X 30m Edited DEM) and the newly acquired time-tagged DEM scenes. In order to keep a unique timestamp, two change maps are available per tile: one with the change to the oldest pixel in the new dataset - the first DEM change, and another with the change to the newest pixel of the new dataset - the last DEM change. The two maps differ only when there are multiple coverages. Users must be aware that a given elevation change measured in the DEM change maps corresponds to a topographic change with respect to TanDEM-X 30m EDEM, but cannot be associated with a corresponding physical height change of the same magnitude. This is due to the fact that the global TanDEM-X DEM reflects an averaged elevation derived from the combination of different images, acquired over a period of several years but also because the radar waves penetrate differently in the surface depending on the attributes of the land cover. This is especially important over vegetated and snow-covered regions.

The TanDEM-X PolarDEM is a project developed by the German Remote Sensing Data Center (DFD) at the German Aerospace Center (DLR) within the activities of the TanDEM-X mission. It is a framework for the provision of derivatives of the global Digital Elevation Model (DEM) of the TanDEM-X mission for Polar Regions. The TanDEM-X PolarDEM 90m of Antarctica is a gap-free and edited version of the TanDEM-X 90m digital elevation model (DEM). The TanDEM-X PolarDEM 90m of Antarctica is provided in Antarctic Polar Stereographic projection (EPSG:3031) with a pixel spacing of 90 meters. The DEM elevation values represent ellipsoidal heights relative to the WGS84 ellipsoid. The majority of the data were acquired between April 2013 and October 2014. The TanDEM-X PolarDEM 90m of Antarctica is split into four tiles. For more information concerning the TanDEM-X PolarDEM, the reader is referred to: https://www.dlr.de/eoc/en/desktopdefault.aspx/tabid-11882/20871_read-66374/

TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) is an Earth observation radar mission that consists of a SAR interferometer built by two almost identical satellites flying in close formation. With a typical separation between the satellites of 120m to 500m a global Digital Elevation Model (DEM) has been generated. The main objective of the TanDEM-X mission is to create a precise 3D map of the Earth's land surfaces that is homogeneous in quality and unprecedented in accuracy. The data acquisition was completed in 2015 and production of the global DEM was completed in September 2016. The absolute height error is with about 1m an order of magnitude below the 10m requirement. The TanDEM-X 90m DEM is a product variant of the global Digital Elevation Model (DEM) acquired in the frame of the German TanDEM-X mission between 2010 and 2015, and has a reduced pixel spacing of 3 arcseconds (90m at the equator). It covers all Earth’s landmasses from pole to pole. For more information concerning the TanDEM-X 90m DEM, the reader is referred to: https://tandemx-90m.dlr.de/ For more information concerning the TanDEM-X mission, the reader is referred to: https://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10378/