Ascending-descending orbit combination for DEM generation is very promising technique which can be used to fill in ome gaps in the DEMs caused by the geometric deformations or SAR images. The benefits from the combination over layover and foreshortening areas are evident thanks to the new data made available over these areas from the opposite pair. However, other areas in the image will also improve its quality because of the averaging between the ascending and the descending pass. This paper shows an ascending descending orbit combination using ERS data. Two ascending and descending DEMs have been calculated independently and a combined DEM has been obtained from them on a coherence basis. The obtained DEMs have been compared with a high accuracy DEM (2m height rms) available. Results show an error reduction in the combined DEM over the ascending and descending ones. Ascending-descending orbit combination SAR interferometry assessment (DEM).