TerraSAR-X/TanDEM-X

Long name TerraSAR-X/TanDEM-X
Short name COS
Sensor type Synthetic-aperture radar (SAR)
Platform TerraSAR-X, TanDEM-X
Frequency 9.65 GHz
Band (wavelength) X (3.1 cm)
Polarization VV, HH, HV, VH
Key file name (use to open data set) *.xml
Supported file extensions *.xml, *.cos, *.tif, *.png, *.txt
Data distributor German Aerospace Center and ASTRIUM (now EADS)
Sections

Data product name and description
Distribution disk files
Returned data for supported format
References

Note: The TanDEM-X satellite, used to measure digital elevation, is twin to the TerraSAR-X satellite.

Data product name and description

The acquisition modes of the TerraSAR-X sensor are as described in the following tables.

Note: The information provided herein is based on the TerraSAR-X reference documentation cited under References.
Mode Swath width (km) Resolution (range x azimuth, m)* Polarization Description/notes
Spotlight [SL] 10

1.2 x 1.1 (Single polarization)
1.2 x 2.2 (Dual polarization)

Single (VV or HH)
Dual (VV and HH)

The Spotlight imaging mode uses phased-array-beam steering in azimuth direction to increase the illumination time; that is, the size of the synthetic aperture, which, however, restricts the image size, scene size, or both.
High-Resolution Spotlight [HS] 10 0.6 x 1.1 Single (VV or HH) Acquisition mode derived from the basic Spotlight [SL] mode.
Staring Spotlight [ST] 4 0.6 x 0.24 Single (VV or HH) Acquisition mode derived from the basic Spotlight [SL] mode.
StripMap [SM]

30 (Single polarization)
15 (Dual polarization)

1.2 x 3.3 (Single polarization)
1.2 x 6.6 (Dual polarization)

Single (VV or HH) Acquisition mode derived from the basic Spotlight [SL] mode.
ScanSAR [SC] 100 1.2 x 18.5 Single (VV or HH) The ScanSAR [SC] mode electronicaly steers the antenna elevation to acquire adjacent, slightly overlapping coverage with different incidence angles that are processed into one scene. A swath width of 100 km or greater is achieved by scanning four adjacent ground subswaths with quasi-simultaneous beams, each with a different incidence angle.
Wide ScanSAR [WS] 270 1.7 x 40 to 3.3 x 40 Single (VV or HH or HV or VH) A swath width of up to 270 kilometers is achieved by scanning six adjacent ground subswaths. Due to the switching between the beams, only bursts of SAR echoes are received, resulting in a reduced bandwidth and, therefore, reduced azimuth resolution.

* Resolution is always single-look complex (SLC) unless noted otherwise.

TerraSAR-X data sets are available for various processing levels, as described in the following table.

Processing level Acquisition mode Description/notes

1B
Single-look, slant range, complex (SSC)

[SL], [HS], [ST]

[SM]

Geometric projection: Azimuth - slant range (time domain).

SSC is a single-look product of the focused radar signal. The pixels are spaced equidistant in azimuth (according to the pulse repetition interval PRI=1/PRF) and in slant range (according to the range sampling frequency). The data is represented as complex numbers containing amplitude and phase information. Each image pixel is processed to zero Doppler coordinates in range direction; that is, perpendicular to the flight track. Due to the nature of azimuth/slant-range coordinates, no geocoding is available.

1B
Multi-look, ground range, detected (MGD)

[SL], [HS], [ST]

[SM]

[SC], [WS]

Geometric projection: Azimuth - ground range (without terrain correction).

MGD is a detected multi-look product with reduced speckle and resolution cells that are approximately square. The image coordinates are oriented along the direction of flight and along ground range. The pixel spacing is equidistant in azimuth and in ground range. With the slant-to-ground-range projection the WGS84 ellipsoid and an average, constant terrain-height value are used.

The advantage of this product is the fact that no image rotation to a map coordinate system has been performed and, therefore, interpolation artefacts are avoided. This product is useful, if you want to geocode or orthorectify the imagery.

1B
Geocoded ellipsoid corrected (GEC)

[SL], [HS], [ST]

[SM]

[SC], [WS]

Geometric projection: Map geometry with ellipsoidal corrections only (without terrain correction).

GEC is a multi-look detected product, which is resampled and projected to the WGS84 reference ellipsoid assuming one average height. The image is represented in map geometry with ellipsoidal corrections only, and no terrain correction is performed. Available grid formats are Universal Transversal Mercator (UTM) and Universal Polar Stereographic (UPS). Because the ellipsoid correction does not use height information from a digital elevation model (DEM) for geometric correction, the pixel location accuracy varies depending on the local terrain. With other types of relief, the terrain-induced SAR-specific distortions are not corrected and significant location shifts can appear, particularly with strong relief, steep incidence angles, or both.

1B
Enhanced ellipsoid corrected (EEC)

[SL], [HS], [ST]

[SM]

[SC], [WS]

Geometric projection: Map geometry with terrain correction using a DEM.

EEC is a multi-look detected product, which is resampled and projected to the WGS84 reference ellipsoid. Image distortions caused by varying terrain height are corrected using an external DEM. The image is represented in map geometry with terrain correction. The available map projections are UTM or UPS.

TerraSAR-X data is also distributed as various enhanced image products, such as ORISAR, RANSAR, MCSAR, OISAR, and ADMSAR, representing a higher level of processing in radiometric correction and orthorectification, mosaics, subsets and merges. Such products have not been tested by PCI Geomatics.

Distribution disk files

TerraSAR-X complex data (SSC) is distributed in COSAR format. Detected data (MGD, GEC, EEC) is distributed in GeoTIFF format.

Warning: Data sets for this sensor are organized in a specific folder structure on disk. GDB uses this structure and the file names to identify the data product type. Do not alter the folder structure or any file names prior to data ingestion to ensure the image data and auxiliary information are imported correctly.
Table 1. COSAR
File name Format Required Contents/details
*.cos Binary Yes

DLR-defined COSAR binary format. Contains image data. One file per polarization.
(IMAGEDATA folder)

*.xml Extensible Markup Language Yes Key file name. Main product annotation file.
GEOREF.xml Extensible Markup Language Yes

Georeference file.
(ANNOTATION folder)

Table 2. GeoTIFF
File name Format Required Contents/details
*.tif GeoTIFF Yes

Image data. One GeoTIFF file per polarization.
(IMAGEDATA folder)

*.xml Extensible Markup Language Yes Key file name. Main product annotation file.
GEOREF.xml Extensible Markup Language Yes

Georeference file.
(ANNOTATION folder)

Returned data for supported format

TerraSAR-X data can be opened directly in its raw vendor format or imported into a PCIDSK (*.pix) file using the key file (*.xml). For optimal processing, use the PCIDSK format.

In the following table, the data structure after it is imported into a PCIDSK file is described (supported processing levels only).

Data product Data returned Details
SSC (Single)

1 x [C16S] raster channel (uncalibrated)
—or—
1 x [C32R] raster channel (calibrated)

1 x [GCP] ground control points
1 x [TEX] main product annotation
1 x [ORB] orbit segment
1 x [BIN] rational function model from state vectors
1 x [ARR] incidence angle array

Data can be calibrated in sigma, beta, or gamma nought.
SSC (Dual)

2 x [C16S] raster channels (uncalibrated)
—or—
2 x [C32R] raster channels (calibrated)

1 x [GCP] ground control points
1 x [TEX] main product annotation
1 x [ORB] orbit segment
1 x [BIN] rational function model from state vectors
1 x [ARR] incidence angle array

Data can be calibrated in sigma, beta, or gamma nought.
SSC (Quad)

4 x [C16S] raster channels (uncalibrated)
—or—
4 x [C32R] raster channels (calibrated)

1 x [GCP] ground control points
1 x [TEX] main product annotation
1 x [ORB] orbit segment
1 x [BIN] rational function model from state vectors
1 x [ARR] incidence angle array

Data can be calibrated in sigma, beta, or gamma nought.
MGD (Single)

1 x [16U] raster channel (uncalibrated)
—or—
1 x [32R] raster channel (calibrated)

1 x [TEX] main product annotation
1 x [ORB] orbit segment
1 x [BIN] rational function model from state vectors
1 x [ARR] incidence angle array

Data can be calibrated in sigma, beta, or gamma nought.
MGD (Dual)

2 x [16U] raster channels (uncalibrated)
—or—
2 x [32R] raster channels (calibrated)

1 x [TEX] main product annotation
1 x [ORB] orbit segment
1 x [BIN] rational function model from state vectors
1 x [ARR] incidence angle array

Data can be calibrated in sigma, beta, or gamma nought.

GEC (Single)
EEC (Single)

1 x [16U] raster channel (uncalibrated)
—or—
1 x [32R] raster channel (calibrated)

1 x [TEX] main product annotation
1 x [ARR] incidence angle array

Data can be calibrated in beta nought.

GEC (Dual)
EEC (Dual)

2 x [16U] raster channels (uncalibrated)
—or—
2 x [32R] raster channels (calibrated)

1 x [TEX] main product annotation
1 x [ARR] incidence angle array

Data can be calibrated in beta nought.

References

German Aerospace Center (DLR), TerraSAR-X Ground Segment: Level 1b Product Format Specification. Issue 1.2, March 27, 2006.

German Aerospace Center (DLR), TerraSAR-X Ground Segment: Basic Product Specification Document. Issue 1.4, June 10, 2006.

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