  A first assessment of the TanDEM-X DEMs over Brazilian territory is presented
through a comparison with SRTM, ASTER GDEM and ALOS AW3D30 DEMs in seven study
areas with distinct geomorphological contexts, vegetation coverage and land
use. Visual analysis and elevation histograms point to a finer effective
spatial resolution of TanDEM-X compared to SRTM and ASTER GDEM. In areas of
open vegetation, TanDEM-X lower elevations indicate a better penetration of the
radar signal. DEMs of differences (DoDs) allowed the identification of issues
inherent to the production methods of the analyzed DEMs, such as mast
oscillations in SRTM data and mismatch between adjacent scenes in ASTER GDEM
and ALOS AW3D30. A systematic difference in elevations between TanDEM-X 12m,
TanDEM-X 30m and SRTM was observed in the steep slopes of the coastal ranges,
related to the moving-window process used to resample the 12m data to a 30m
pixel size. Due its simplicity, it is strongly recommended to produce a DoD
with SRTM before using ASTER GDEM or ALOS AW3D30 in any analysis, to evaluate
if the area of interest is affected by these problems. The DoDs also
highlighted changes in land use in the time span between the acquisition of
SRTM (2000) and TanDEM-X (2013) data, whether by natural causes or by human
interference in the environment.
