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 DEM Change Maps - is available in 30m posting and show 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 penetrates differently in the surface depending on the attributes of the land cover. This is especially important over vegetated and snow-covered regions.
DLR © 2023