Operational process interferometric for the generation of a digital model of ground Applied to the couple of images ERS-1 ERS-2 to the area of Algiers F. Hocine, M.Ouarzeddine, A. Belhadj-aissa, , M. Belhadj-aissa, , Y. Smara Faculty of Electronics and Computer Science Houari Boumediene University of Sciences and Technology, Image Processing and Radiation Laboratory, Algiers Faiza_ho@yahoo.fr , m.ouarzeddine@lycos.com , h.belhadj@lycos.com , mbelhadjaissa@yahoo.com , y.smara@lycos.com , ABSTRACT The data used is a couple of SLC (Single Look Complexe) images acquired in the Tandem mission of the ERS1 (3 January 1996 ), ERS2 ( 4 January 1996 ) satellites. The area is a part of Algiers. Three basic steps in the interferometric procedure are necessary: the coo-registration using the orbital parameters, the interferometric product and the correction of the interferogram from the flat earth effect and the third step is the phase unwrapping which has been realised using the least square method. In parallel the coherence map has been generated to assess the interferogram quality. 1 INTRODUCTION Radar interferometry is a technique which allow the evaluation of the altitude of a point in the ground and detect the small displacement of the ground. This technique is based on the use of two radar images of the same scene acquired by two antennas separated by a distance named the baseline [1]. We present the interferometric process we have developed to obtain a Digital Terrain Model (DTM). 2 FORMULATION The phase of SAR image is rich of information but difficult to be explored. The phase difference ) ( p φ ∆ measured between the two acquisitions is given by Eq.1. ) ( 4 ) ( ) ( ) ( B A B A R R p p p − = − = ∆ λ π φ φ φ (1) The phase difference between the two signals is directly related to the elevation h:                 − = B R R B A arcsin cos R - H h A (2) Where: B Component of the baseline λ Wavelength θ Incidence angle (23° To the centre of the scene) A B R R − : R ∆ range difference