Contribution of Automatic Processing of LiDAR Data to Accelerate Topographic Map Updating

The process of topographic maps updating in the Moroccan Agency for Land Registration, Cadaster and Cartography (ANCFCC) is essentially performed by manual 2D or 3D plotting based on aerial or satellite images. In this chapter, we use data from airborne LiDAR to automatically extract some map features for the purpose of speeding up the map updating process. We processed LiDAR data with both ArcGIS and QGIS Grass software to automatically generate some map data layers like contour lines and hydrography streams. The obtained features were compared by overlapping other data such as orthoimages, manually stereoplot map and contour lines generated after automatic photogrammetric correlation in the same area. The comparison of all datasets showed that LiDAR can bring a significant advantage in some areas like shaded areas of aerial images or areas of complex topographic structures like cliffs as well as in dense forest zones or even relatively urban areas where classic stereoplotting often presents difficulties. However, automatic processing of LiDAR data requires adapted parameters to avoid poorly or over detailed maps, particularly with hydrographic features even if the automatically obtained hydrographic streams present the advantage of being ordered following the stream size. We conclude that automated LiDAR data processing is of high value in terms of accelerating map updating and the extracted features like contours and hydrographic streams are of better quality than traditional methods.