Quality Assessment of Dtm and Orthophoto Generated by Airborne Laser Scanning System Using Automated Digital Photogrammetry

The approach of using an airborne laser scanning for DTM generation has made great progress recently. However, it is not always clear the reliability and the quality of the geometry that characterise the generated DTM. Thus, a special test was conducted to assess the quality and the reliability of the generated DTM via an airborne laser scanning system. To perform this test, an airborne laser scanner aligned with an airborne digital camera was mounted on a Helicopter (TopEye AB system). The test was performed in Italy and the flying height was about 200 meter. An overlap percentage of 50% were maintained between two successive images. The digital camera is a Hasselblad camera with 2Kx3K resolution. An INS/GPS system is integrated and used for position and orientation determination. A series of tests were done to check the DTM quality. The main approach used is based on comparing it to the DTM generated from the digital aerial photogrammetry (automatic and semi-automatic matching approaches). Additional comparison is conducted between the Orthophoto created by stereoscopic model and the one created by the laser data and digital images. The test results will be presented and discussed.