The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Voi. XXXVII. Part Bl. Beijing 2008 
coordinates are oriented along flight direction and along ground 
range. A simple polynomial projection is performed in range to 
an ellipsoid in order to achieve approximately quadratic pixels. 
The advantage of this product is the fact that no image rotation 
to a map coordinate system has been performed and 
interpolation artefacts are thus avoided (Fig. 5). 
rg 
Fig. 5: Solothurn (Switzerland) - SL- MGD product 
1.2.3 The Geocoded Ellipsoid Corrected (GEC) product 
The product corresponds to the ERS-1/2 GEC or the ENVISAT 
SAR product called ASA_IMG_1P. 
The GEC is a multi-look detected product. It is projected and 
resampled to either UTM or UPS with WGS84 as reference and 
assuming one average terrain height. The pixel spacing is 
equidistant in northing and easting. 
As the ellipsoid correction does not consider a DEM, the pixel 
location accuracy varies due to the terrain. 
The GEC is the recommended product for marine and coastal 
applications where topography doesn’t affect the location 
accuracy (Fig 6). 
Fig. 6: Solothurn (Switzerland) - SL - GEC product 
1.2.4 Enhanced Ellipsoid Corrected (EEC) product 
The product corresponds to the ERS-1/2 GTC or the ENVISAT 
ASAR DLR-Value-added products. 
Like the GEC, the EEC is a multi-look detected product 
provided in UTM or UPS projection. WGS84 will be used as 
the geodetic datum. Terrain induced distortions are corrected 
considering a DEM of a moderately coarser resolution then the 
TerraSAR-X products. The pixel location accuracy in these 
products is highly precise. The geometric quality depends on the 
height accuracy and resolution of the DEM in combination with 
the type of terrain and the incidence angle. DEMs from SRTM 
(C-band and X-SAR), ERS-derived elevation models and 
GLOBE provide a global basis for a terrain correction service 
(Roth et al., 2004). The orbit precision will be the main factor 
for the achieved location accuracy. Depending on the time delay 
between acquisition and processing, predicted (±700 m), rapid 
(±2 m) or science orbits (±20 cm) will be used for the 
geocoding (Roth et al., 2004). 
Fig. 7: Solothurn (Switzerland) - SL- EEC product 
In contrast to ERS-1/2 and EN VIS AT/AS AR products, two 
resolution variants will be offered for each of the detected 
products MGD, GEC and EEC. One is optimised with respect to 
the spatial, the other with respect to radiometric resolution. The 
spatially enhanced (SE) product is designed for the highest 
possible ground resolution while the radiometrically enhanced 
(RE) variant improves the radiometry by multi-looking. 
2. TERRASAR-X VALUE-ADDED PRODUCTS 
The Value Added Products are based on TerraSAR-X Basic 
Image Products and can be generated from new acquisitions, 
catalogue orders, or a combination of both. They represent a 
higher level of image processing (also called Enhanced Image 
(El) Products). 
2.1 Value-Added Product Description 
2.1.1 Radiometrically corrected image - RaN SAR 
Calibration of the backscatter values is necessary for inter 
comparison of radar images acquired with different sensors, or 
even of images obtained by the same sensor if acquired in 
different modes or processed with different processors. 
The Basic Image Products GEC and EEC are delivered as radar 
brightness (Po)- Further radiometric corrections, compensating 
for effects of local pixel scattering area and local incidence 
angle on the local backscatter, can be carried out. Two different 
kinds of radiometric corrections; radiometric calibration and 
normalization will lead to an absolute measurement of the 
sigma naught (o°) or gamma naught (y°) coefficients 
respectively, depending on the customer’s selection. 
• Radiometric calibration: resulting in sigma naught 
(°o)-