TerraSAR-X ELEVATION Product Suite

Infoterra GmbH, the wholly-owned subsidiary of EADS Astrium that holds the exclusive commercial exploitation rights for the high-resolution radar satellite TerraSAR-X, has announced the first element of its TerraSAR-X ELEVATION product suite.

Featuring a 10m grid spacing and an absolute height accuracy of up to 5m, the TerraSAR-X ELEVATION DSM (digital surface model) is now operationally available for areas as small as only 500 sqkm, and up to full regional coverage, worldwide. Particularly the unique reliability of the weather-independent radar sensor makes this an ideal complement to the established Spot Infoterra portfolio of elevation data sets such as Reference 3D, based on SPOT HRS optical data.

"In addition to this unique reliability and the resulting time- and cost-efficient data acquisition, customers will particularly appreciate our flexible delivery concept;" Dr. Gertrud Riegler, Product Manager for Digital Elevation Models at Infoterra, explains: "It allows the users to adapt the scope of delivery to their individual requirements, as a set of auxiliary layers and the corresponding orthorectified image are optional additions to our TerraSAR-X ELEVATION DSM."

As the propagation of the radar beam can be measured very precisely, with the satellite featuring a unique positional accuracy, the extracted height information is based on very solid input: TerraSAR-X StripMap stereo pairs, acquired in both ascending and descending orbit directions, are processed automatically, applying radargrammetry techniques. With algorithms specifically developed for this purpose, outliers, artefacts and gaps are identified and corrected. Water body features derived from corresponding TerraSAR-X image data are included and a subsequent manual editing of shorelines guarantees hydrological consistency.

This novel approach enables Infoterra to offer highly time-efficient production schemes: "Full data acquisition and production for our minimum order unit of 500 sqkm can be carried out within about one month. For areas of about 500.000 sqkm, customers can expect the delivery within a year after ordering," Dr. Riegler says, and then confidently assures the unique quality of the TerraSAR-X ELEVATION DSM products: "The product's performance and accuracy values were determined in an extensive validation and verification campaign. In order to asses various terrain and land cover types; we have covered more than 15 test sites worldwide, with high-quality reference data available for each."

Precise elevation data is the initial foundation of any accurate geospatial product, particularly when the integration of multi-source imagery and data is performed based upon it. Topographic mapping, communications network planning, hydrologic modelling, air traffic security and, last but not least, the reliable orthorectification of high-resolution satellite imagery are only examples of the wide range of applications that benefit from precise, reliable elevation data.

Infoterra is thus working towards expanding the Spot Infoterra elevation data portfolio even further: today, radar-based Digital Terrain Models (DTM), a representation of the ground surface as so-called bare-earth terrain, are available tailor-made. An operational processing facility to generate standardised DTMs (TerraSAR-X ELEVATION DTM) is currently under development and expected to be implemented in 2010.

Lastly, the upcoming TanDEM-X mission, where TerraSAR-X and its "twin" TanDEM-X will be collecting interferometric data synchronously, has significant potentials in store: Together, the twin satellites will be collecting the data basis for a complete global elevation model, unprecedented in coverage and accuracy. TanDEM-X is scheduled to be launched on June 21, 2010; global elevation data products are expected to be available from 2013.

Sample data sets are available for free download on www.infoterra.de.