Methods of identification and delimitation of concave terrain features based on ISOK-NMT data

Airborne Laser Scanning (ALS) products are now often used to study the terrain due to their numerous advantages such as relatively low cost and ease of data collection. The ISOK project (pl: Informatyczny System Osłony Kraju – national hazard protection information system) developed elevation data for about 65% of the Polish territory. Parallel to the airborne laser scanning point cloud collection, additional products, such as orthophotomaps, digital terrain models (DTM), and digital surface models (DSM) were created. This resource is not only a reference material for the project, but also a valuable source of the analysis used in various fields of economy and science. Important features of the ISOK-data are the availability and their standardized format based on uniform technical conditions. The article presents the results of an experiment in which an attempt was made to use the digital elevation model with a resolution of 1 m based on airborne laser scanning data to determine concave terrain features using GIS tools. The ISOK-DTM has a height accuracy of 0.15 m for the outdoor areas, which makes it a better representation of small terrain forms than previous products. The research area is located at an undeveloped open ground with comparatively little variation of its shape for a long period. Several methods were tested to classify the terrain shape based of topographic attributes. Those methods led to similar locations of the concave features and further on coincide with results of the pre-analysis. Also, attention was drawn to the selection of the analysis parameters and their influence on the result. The results show the usefulness of ISOK’s DTM for locating field concave terrain shapes.