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Numeryczne dane wysokościowe misji TanDEM-X

Woroszkiewicz M.

Biuletyn Wojskowej Akademii Technicznej

2015

Vol. 64, nr 1

33-46

Zapoczątkowana w 2010 roku misja TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) jest pierwszą satelitarną misją radarową, w ramach której zostały pozyskane dane interferometryczne w trybie bistatic InSARstripmap przez dwa bliźniacze satelity TerraSAR-X (TSX) oraz TanDEM-X (TDX) tworzące formację Helix. Realizacja tej konfiguracji ma na celu budowę numerycznego modelu pokrycia terenu (NMPT) o zasięgu globalnym w standardzie HRTI-3 (High Resolution Terrain Information). W artykule przedstawiono opis i specyfikację podstawowych produktów misji, jakimi są m.in. numeryczne modele pokrycia terenu, a także dodatkowych komponentów w postaci warstw informacyjnych i masek. Opisane zostało również zastosowanie techniki interferometrii radarowej w procesie budowy numerycznego modelu pokrycia terenu w postaci cyfrowej.

Started in 2010 TanDEM-X mission (TerraSAR-X add-on for Digital Elevation Measurement) is the first space borne radar interferometer mission that acquires interferometric data in bistatic InSARstripmap mode with two spacecrafts TerraSAR-X (TSX) and TanDEM-X (TDX) flying in Helix formation. That configuration enables generation of a global digital elevation model compatible with the HRTI-3 standard. This paper presents an overview and specification of primary products of the TanDEM-X mission, i.e. digital elevation models and additional components such as information layers and masks. Moreover, the use of radar interferometry techniques for generation of the digital elevation model (DEM) and applications of InSARare discribed.

Optimizing the minimum cost flow algorithm for the phase unwrapping process in SAR radar

Dudczyk J., Kawalec A.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2014

Vol. 62, nr 3

511--516

The last three decades have been abundant in various solutions to the problem of Phase Unwrapping in a SAR radar. Basically, all the existing techniques of Phase Unwrapping are based on the assumption that it is possible to determine discrete ”derivatives” of the unwrapped phase. In this case a discrete derivative of the unwrapped phase means a phase difference (phase gradient) between the adjacent pixels if the absolute value of this difference is less than π. The unwrapped phase can be reconstructed from these discrete derivatives by adding a constant multiple of 2π. These methods differ in that the above hypothesis may be false in some image points. Therefore, discrete derivatives determining the unwrapped phase will be discontinuous, which means they will not form an irrotational vector field. Methods utilising branch-cuts unwrap the phase by summing up specific discrete partial derivatives of the unwrapped phase along a path. Such an approach enables internally cohesive results to be obtained. Possible summing paths are limited by branch-cuts, which must not be intersected. These branch-cuts connect local discontinuities of discrete partial derivatives. The authors of this paper performed parametrization of the Minimum Cost Flow algorithm by changing the parameter determining the size of a tile, into which the input image is divided, and changing the extent of overlapping of two adjacent tiles. It was the basis for determining the optimum (in terms of minimum Phase Unwrapping time) performance of the Minimum Cost Flow algorithm in the aspect of those parameters.