Dem Evaluation Generated from Hrs Spot5 Data

The purpose of this project is to test High Resolution Stereoscopic (HRS) data of SPOT5. This project is done in the framework of the “HRS study Team” international test, supported by ISPRS-CNES. The Digital Elevation Model (DEM) was derived from the HRS data and was evaluated by using a 3D reference data set. The study site for HRS data is located in Manosque, France. It is a countryside landscape, with fields and villages. The height relief is medium and in some areas considerably intensive. The HRS data was acquired on 14 August 2002. A number of different DEM generation experiments were carried out, in order to examine the influence of different processing parameters on the final accuracy of the DEM. Thus: 1) The same date acquisition of the stereo-pair reduces the radiometric variations of images; nevertheless, the fact that the images are captured by two different sensors has led us to apply a histogram matching technique for image pre-processing, in some experiments. 2) The georeferencing and the stereo model set-up of the images were established in four different ways: by using only the metadata; by using the metadata and tie points that have been generated automatically; by using the metadata, tie points that have been generated automatically and some tie points that have been derived manually; The same as the second solution but in the triangulation process 6 GCP’s (XYZ coordinates) have been used. For the extraction of the GCP’s an additional procedure has been performed, which consisted basically of the production of an orthoimage based on the reference DEM. The study of the accuracy statistic results of 8 different derived DEM,s showed that the elevation accuracy was better, about 0-5 m, in flat and even areas than in mountainous and steep areas.