012 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
de e dE Ce A 3.2.2 Test Site Virginia, USA: The second test site consists
of 7 acquisitions covering an area from North Carolina up to
Lake Ontario. Figure 6 shows the amplitude mosaick
superimposed by the color shaded DEM of tile N39W79 and
the RawDEM outlines (red). Note that RawDEMs with
insufficient quality, e.g. because of large phase unwrapping
errors, have to be reprocessed and were not used for IDEM
generation.
The selected DEM tile N39W79 is located in the Appalachian
Mountains and thus hilly and forested. The coherence in the
SAR image is generally lower over forested areas. This causes
noisy DEM values and has also an impact on the quality of
calibration points. The calculated offsets and tilts are below 4m
and 3cm/km respectively.
A high resolution USGS Seamless DEM is available for this
Um : T. area. The USGS Seamless data is a terrain model and therefore
: ; T o. > has to be compared with caution to the TanDEM-X DEM,
Figure 4: Difference between TanDEM-X and SRTM-C which is actually a surface model. This explains the “high”
tile N49W98, range of values [-10; 10] mean offset of almost 10m (Table 2). However, in areas with
less vegetation (green areas in Figure 7) the difference is in the
SEN AS range of about 2m. The comparison to ICESat results in a mean
pu difference of -3.67m with a standard deviation of 6.68m (Figure
m 8). The difference to SRTM shows a mean offset of 6.33m and a
standard deviation of 4.51m (Figure 9).
bs The relative height accuracy, estimated by calculating the
absolute differences between neighboring acquisitions, is well
below 3m (Figure 10).
Diffotencas-Datwonon-Neighbors
irked red,
reen
Reference Mean Std.dev | LE90 | # points
[m] [m] [m]
USGS 9.94 8.20 12.39 all
E: ICESat -3.67 6.68 10.94 1140
SRTM 6.33 4.51 6.85 all
x Neighbor 2.67 2.72 3.00 all
: Sg QUEE $ æ Table 2: Differences of IDEM tile N39W79 to reference data
"S on Figure 5: Difference between neighboring acquisitions, (mean, standard deviation, linear 90% point-to-point error,
98 - area tile N49W98, range of values [0; 3] number of points)
TundEM-x + Mich. Roc, RofDen
Figure 7: Difference between DEM tile N39W79 and USGS
Seamless reference DEM (range of values [-20; 20])
4E crus ; E Le
Sat on Figure 6: Overview test site Virginia. Color shaded DEM of tile
ES: 5] N39W79 superimposed on amplitude mosaick, RawDEMs
marked red
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