DEM Extraction from High Resolution Satellite Stereopairs to Investigate the Hydraulic Hazard of Area Subjected to Rivers Flood

As far as the monitoring of the hydraulic hazard of flat areas is concerned, a very important role is played by studies concerning the outflow of water after river floods or downpours. Such studies are based on complex forecasting hydraulic models, which need an accurate and detailed DSM as input together with planimetric and altimetric data regarding all the natural and anthropic objects, as riverbanks or roads in relief, which may interfere with the outflow of water. The aim of this work is the evaluation of DSMs extracted from high resolution stereo pairs for their application in hydraulic hazard analysis. The advantages arising from the use of satellite images are mainly relative low costs and fast elaboration. The investigation has been carried out on an in-track Ikonos stereopair acquired over the area of the town of Ferrara (Northeastern Italy, near the Po delta) on July 2004. The best workflow to generate the DSM has been evaluated: the orientation has been performed both with the commercial software PCI Geomatics OrthoEngine v10.2 and with the scientific software SISAR, developed by La Sapienza University of Rome. Image matching and DSM extraction have been performed with PCI Geomatics and SISAR matching facility but also, for the image matching, with the scientific software DPCOR, developed by Leibniz University of Hannover. The DSM accuracy has been evaluated comparing a reference DSM derived from a recent photogrammetric flight with all the extracted DSMs.