ABSTRACT
Due to the turbulent history extremely reach and unique resources of military architectural objects (modern fortification complexes) are located in Poland. The paper presents results of analysis of utilization of aerial laser scanning data for identification and visualization of forts in Poland. A cloud of point from the ISOK Projects has been utilized for that purpose. Two types of areas are distinguished in this Project, covered by products of diversified standards: standards II - laser scanning of the increased density (12 points per sq.m.), standard I - laser scanning of the basic density (4 points per sq.m.). Investigations were carried out concerning the quality of geospatial data classification with respect to further topographic analysis of fortifications. These investigations were performed for four test sites, two test sites for each standard. Objects were selected in such a way that fortifications were characterized by the sufficient level of restoration and that at least one point located in forest and one point located in an open area could be located for each standard. The preliminary verification of the classification correctness was performed with the use of ArcGIS 10.1 software package, basing on the shaded Digital Elevation Model (DEM) and the Digital Fortification Model (DFM), an orthophotomap and the analysis of sections of the spatial cloud of points. Changes of classification of point clouds were introduced with the use of TerraSolid software package. Basing on the performed analysis two groups of errors of point cloud classification were detected. In the first group fragments of fortification facilities were classified with errors; in the case of the second group - entire elements of fortifications were classified with errors or they remained unclassified. The first type error, which occurs in the majority of cases, results in errors of 24 meters in object locations and variations of elevations of those fragments of DFM, which achieve up to 14 m. At present, fortifications are partially or entirely covered with forests or invasive vegetation. Therefore, the influence of the land cover and the terrain slope on the DEM quality, obtained from Lidar data, should be considered in evaluation of the ISOK data potential for topographic investigations of fortifications. Investigations performed in the world proved that if the area is covered by dense, 70 year old forests, where forest clearance is not performed, this may result in double decrease of the created DTM. (comparing to the open area). In the summary it may be stressed that performed experimental works proved the high usefulness of ISOK laser scanning data for identification of forms of fortifications and for their visualization. As opposed to conventional information acquisition methods (field inventory together with historical documents), laser scanning data is the new generation of geospatial data. They create the possibility to develop the new technology, to be utilized in protection and inventory of military architectural objects in Poland.