D., 2012.
i-channel
ng, IEEE
. Glacier
tracking.
pp. 394—
Gay, M.,
Jombrun,
1d Bolon,
by multi-
irements.
ote Sens-
ng: from
, G. and
by maxi-
iE Trans.
à K, $.,
cher, in-
; pp. 87-
tochastic
lorn, R.,
e aletsch
y. Geo-
419—430.
1, E. and
it alpiner
rometrie.
130.
mler, R.,
xploiting
1 of Pho-
olarimet-
logy 17,
; F. and
n. Geo-
p. 2861—
aracteris-
ournal of
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
THE GLOBAL TANDEM-X DEM:
PRODUCTION STATUS AND FIRST VALIDATION RESULTS
M. Huber* *, A. Gruber*, A. Wendleder “, B. Wessel ?, A. Roth *, A. Schmitt?
* DLR, German Aerospace Center, 82234 Wessling Oberpfaffenhofen, Germany - (martin.huber, astrid.gruber,
anna.wendleder, birgit.wessel, achim.roth, andreas.schmitt)@dir.de
KEY WORDS: TanDEM-X, DEM, InSAR, Global, Calibration, Mosaic, Block Adjustment, Validation
ABSTRACT:
The TanDEM-X mission will derive a global digital elevation model (DEM) with satellite SAR interferometry. Two radar satellites
(TerraSAR-X and TanDEM-X) will map the Earth in a resolution and accuracy with an absolute height error of 10m and a relative
height error of 2m for 90% of the data. In order to fulfill the height requirements in general two global coverages are acquired and
processed. Besides the final TanDEM-X DEM, an intermediate DEM with reduced accuracy is produced after the first coverage is
completed. The last step in the whole workflow for generating the TanDEM-X DEM is the calibration of remaining systematic
height errors and the merge of single acquisitions to 1°x1° DEM tiles. In this paper the current status of generating the intermediate
DEM and first validation results based on GPS tracks, laser scanning DEMs, SRTM data and ICESat points are shown for different
test sites.
1. INTRODUCTION
The final product of the TanDEM-X mission (Krieger et al.
2007) will be a global digital elevation model (DEM) with an
absolute height error of 10m and a relative height error of 2m
for 90% of the data, respectively. For this purpose at least two
global coverages will be acquired with SAR interferometry.
Areas with undulated terrain will be also observed from
ascending and descending orbits, where necessary.
As a pre-version, the intermediate DEM (IDEM) will be
produced for selected areas utilizing the first global coverage
only. Even though the IDEM will not have the final TanDEM-X
DEM accuracy, it provides a first impression on the prospective
quality of this product.
In Chapter 2 the Mosaicking and Calibration Processor which
stands at the end of the whole workflow for generating the
TanDEM-X DEM is outlined. Then in Chapter 3 the current
production status and validation results for different test sites
and different reference data are shown. Additional product
layers like height error map, amplitude image, water indication
mask, coverage map, layover and shadow mask, interpolation
mask and void mask are presented in Chapter 4.
2. MOSAICKING AND CALIBRATION PROCESSOR
Smaller systematic errors in the order of a few meters still
remain in single acquisitions, although intensive instrument
calibration and high precision orbit and baseline determination
are conducted (Hueso et al. 2011).
Based on these acquisitions, which can be hundreds of
kilometers long, the Integrated TanDEM-X Processor (ITP)
generates single interferometric DEMs (Fritz et al. 2008). This
so-called RawDEMs, having a size of typically 30km by 50km,
serve as input for the Mosaicking and Calibration Processor
(MCP). The MCP consists of three components which are
working independently from each other.
* Corresponding author.
45
2.1 MCP Preparation
The first MCP component, the DEM Preparation processor, is a
data-driven process. A first analysis of the RawDEM is
performed which comprises a height discrepancy detection to a
reference DEM (e.g. SRTM), a water body detection
(Wendleder et al. 2012) and the extraction of calibration points
(Huber et al. 2009, Huber et al. 2010) as input for the DEM
calibration processor. After interactive quality control the result
is stored for later processing.
2.2 MCP Calibration
The second component, the DEM Calibration Processor, is
initiated by an operator. A processing request for a dedicated
region is generated and sent to MCP. During the DEM
Calibration a block adjustment procedure calculates offsets and
tilts for each DEM acquisition (Gruber et al. 2009, Wessel et al.
2009). Therein, the elevation of tie-points in overlapping
regions and ICESat points collected during MCP preparation
are used to assure the relative and absolute height accuracy
requirement. After quality control the correction parameters are
stored within the annotation information for each RawDEM.
2.3 MCP Mosaicking
The third processor, the DEM Mosaicking Processor, is also
initiated by an operator. A request for a defined region is
generated and sent to MCP. Then, the DEM layers and
additional information layers of all RawDEMSs are mosaicked.
After final quality control the mosaicked DEM is divided into
DEM product tiles and archived.
