Assessment of Lidar Dtm Accuracy in Coastal Vegetated Areas

Digital terrain models (DTM’s) are widely used in coastal engineering. Reliable height information is necessary for different purposes such as calculating flood risk scenarios, change detection of morphological objects and hydrographic numeric modelling. In this specific field light detection and ranging (lidar) replaces step by step other methods such as terrestrial surveying. However, some new problems are associated with lidar technology. For instance, in vegetated areas the accuracy of the lidar DTM decreases. In this paper the influence of different types of coastal vegetation on the accuracy of the lidar height information is investigated. For that purpose this research starts with a comparison of terrestrial control measurements and the lidar data in order to detect problematic areas with respect to the accuracy of the DTM. Based on the resulting height differences the influence of different attributes of the vegetation, i.e. type, height, density, is analysed. In the next step typical features, which are able to describe the attributes, are extracted from the available remote sensing and GIS data (ranging from laser heights and intensity information to multispectral images and biotope mapping). These features were used to perform a classification of the lidar data in different categories of accuracy. Finally, first results for two test areas are presented.