Lidar Filtering: Testing of an Automatic Procedure Developed in the Free Open Source Gis Grass

The goal of this study was to analyze the filtering performance of LiDAR data of an algorithm implemented by our group of research. The algorithm is completely automatic and needs only the raw data classified as first and last pulses. It was implemented in the open source software GRASS and it is composed of three functions that have to be launched in sequence: v.lidar.edgedetection, v.lidar.growing and v.lidar.correction. Starting from the classified points, the algorithm can performed a grid DTM/DSM. The check of the algorithm quality was carried out with a dataset that represents a real case, being already used to create a DTM/DSM along some urbanized areas of Sardinia Region Coast, in Italy. The first control regarded the filtering performance of the implemented algorithm. It was performed by comparing our results with those one obtained by TopScan, a German company which executed the same processing on behalf of Sardinia Region, using a preliminary automatic algorithm followed by a manual correction. Sardinia’s products were checked by visual comparison with high resolution orthophotos (12.5 cm) and with terrain survey measurements. We assumed Sardinia’s classification as a reference. Another control was then carried out to check the gridded products (DTM and DSM) with GPS measurements.Lastly, we checked the computational performances in terms of time when the adopted resolution of the grid DTM/DSM varies.