Digital Terrain Model Reconstruction in Urban Areas from Airborne Laser Scanning Data: the Method and the Example of the Town of Pavia (northern Italy)

Lidar techniques represent a new and fruitful approach in the determination of digital surface models. One of the goals in processing this data is to set up filtering methods allowing to automatically extract the ground and the features (buildings, vegetation,...) superimposed on the terrain itself. In our work the emphasis is posed on the first topic. The method implemented took advantage of the use of spline functions regularized by means of Tychonov functional in a least squares approach. The DSM pixels have been classified in order to previously detect the edges of the non terrain features; the second step is the identification of all the pixels corresponding to the ground, by means of a region growing algorithm and its correction. By a new interpolation only made from the ground pixel we finally get to the digital terrain model. In the paper the processing methodology is discussed and a first large real example is presented.