In this paper we propose a new methodology to estimate the absolute Digital Elevation Model (DEM) of an area by radargammetric-like processing of interferometric multi-baseline SAR data from two opposite-side surveys. First, two separate DEMs of the imaged area are obtained from two opposite-side tomographic SAR views. Both the DEMs thus obtained are affected by residual baseline errors. Coregistration of the DEMs is thus performed, so as to correct these errors. This methodology combines the great accuracy of multi-baseline interferometric processing with precise stereo plotting typical of opposite-side radargrammetry, requires no texture matching and no control points and can be applied also in the case of few a-priori information about the site topography.