International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
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Figure 8: Difference between TanDEM-X and ICESat on 
amplitude mosaick, tile N39W79, range of values [-3; 3] 
  
TanDEM-SRTM Yet ape 13 12.47 M23 
  
  
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Figure 9: Difference between TanDEM-X and SRTM-C, 
tile N39W79, range of values [-20; 20] 
Differences-Between-Meighbors EEE 
  
   
   
  
Figure 10: Difference between neighboring acquisitions, 
tile N39W79, range of values [0; 6] 
     
  
  
  
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4. ADDITIONAL PRODUCT LAYERS 
Along with the digital elevation model, which is the main 
product of the TanDEM-X mission, additional information 
layers will be available. These additional layers are congruent 
with the DEM and have the same nominal spacing of 0.4 
arcseconds. As mentioned above, the products are delivered in 
1°x1° tiles and comprise the following layers: 
Height Error Map — HEM: 
The values represent the random height error for each DEM 
pixel in form of the standard deviation. The value is derived 
from the interferometric coherence and geometrical 
consideration and thus represents the result of rigorous error 
propagation. 
Layover and Shadow Mask — LSM: 
The values represent flags where layover and shadow areas are 
identified. The shadow information is based on (SRTM-C and 
GLOBE) and will therefore only be a rough estimate for many 
regions. The layover is based on the TanDEM-X DEM. 
Void Mask — VOM: 
The values represent flags where larger height inconsistencies, 
like differences above a predefined threshold (e.g. 10m) 
between different DEM acquisitions occur. These pixels should 
be masked out in the elevation model in order to obtain a more 
reliable DEM. 
Water Indication Mask — WAM: 
The values represent flags where water bodies are identified 
during processing. Water is identified by three different 
extraction methods: 
- with a strong amplitude threshold, normally < 40 digital 
number (DN) 
- with a more relaxed amplitude threshold, normally < 60 DN 
- with a coherence threshold, normally < 0.23 
The number of occurrences reflects the number of single 
acquisitions fulfilling the respective threshold. The maximum 
number of annotated occurrences for each method is three. 
Interpolation Mask — [PM: 
The values indicate pixel where small spikes and wells were 
interpolated. 
Coverage Mask — COV: 
The values indicate the number of acquisitions contributing a 
valid DEM pixel to the elevation model. 
Amplitude Mosaick - AMP: 
The values represent the mosaic of the geocoded SAR 
amplitude images corresponding to the active channel of the 
DEM acquisitions. 
Detailed information about the TanDEM-X product (DEM and 
additional layers) can be found in the “TanDEM-X DEM 
Product Specification" (TanDEM-X Ground Segment 2011). 
In the following a subset of approximately 8km x 8km was 
extracted in full 0.4 x 0.4 arcsecond resolution 30 km east of 
Jacksonville, North Carolina from the tile N34W78 (center of 
subset — 34?46"N, 77?9"W). The result of the WAM extraction 
is exemplarily depicted for tis subset. The amplitude image 
shows a river expanding towards its water mouth into the 
Atlantic (Figure 11). The corresponding height values in the 
DEM appear noisy as interferometric data sets have generally 
low coherence over water (Figure 12). On the over hand details 
like the clear-cut for the railroad route running from east to west 
are clearly visible (slightly left of the center). 
Figure 13 shows the Height Error Map where bright values 
indicate larger height error and lower coherence, respectively.