[gdal-dev] [GDAL TerraSAR-X] TDX products

[Usseglio Gaelle (THALES SERVICES NUMERIQUES)]

Hello,

I am using GDAL through OTB (the Orfeo Toolbox) to process TSX/TDX products with the specific driver: COSAR/COSAR Annotated Binary Matrix (TerraSAR-X).

With TSX products, the driver works fine.
I have also tried to read CoSAR files from TDX products. Data have a huge difference with a floating point data format instead of integer values. This floating format is a specific format called "Half Precision Floating Point" for each of the complex values. Thus, TDX products are not well-interpreted. Further information are available in TD-GS-PS-3028_TanDEM-X-Experimental-Product-Description_1.2. The annotations seem to be the same than TSX products.

I need your help to include this new format in GDAL and so in OTB.

As far as I can understand, the specific driver for CoSAR binaries is implemented in https://github.com/OSGeo/gdal/blob/master/gdal/frmts/cosar/cosar_dataset.cpp. The data type is set to GDT_CInt16. I think that explains why TDX are not well-interpreted. In my opinion, in order to include TDX products a conversion has to be made before assigning the buffer. I have found an algorithm to convert "half float" to single float : http://blog.schmorp.de/data/binary16/fasthalffloatconversion.pdf

Do you think, is it possible to implement this feature in GDAL?

Regards,
Gaëlle.

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Gaëlle Usseglio -Thales Services
Responsable de prestation : Support HPC (Portages, Optimisations, Audits, Expertises, etc.)

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