DEM generation from native stereo VENµS acquisitions

VENµS is an Earth observation mission which main purpose is to acquire images over 123 scientific sites spread around the world to monitor vegetation and land surface processes. In order to fulfil this goal, VENµS provides 5m resolution orthorectified images acquired every two days with constant viewing angle for multi-temporal analysis. Images contains 12 bands: 11 different spectral shortwave bands, and 1 redundant band (B06) which has the same spectral content as B05. Their B/H is 0.025, allowing us to compute a Digital Elevation Model from a single acquisition.

The DEM is computed from a single product in the sensor geometry of the two spectral bands B05 and B06. Radiometric corrections are applied (equalization, straylight correction). The geometric model is refined using ground control points computed between the current image and Venµs reference image. This allows to correct attitude restitution errors.

A subpixel correlation is computed between B05 and B06 bands to find homologous points. Images are not resampled in order to avoid adding noise from the resampling process. The shift due to the acquisition time difference between B05 and B06 is taken into account directly into the correlation process. Then, the intersection of viewing directions is assessed from each couple of homologous points found, providing altitudes.

Due to residual restitution attitude errors, we study the benefit of adding other bands correlation in the DEM creation process. The purpose is to robustify the calculation of viewing direction intersection and improve DEM quality. DEM quality is assessed compared to an external reference DTM.