Semi-automatic detection of burial mounds in forested areas

This paper describes a new method for the automatic detection of heap structures in airborne laser scanning data, and reports on a work in progress. The heaps could be ancient grave mounds, dating to 1500-2000 years ago. Such grave mounds are automatically protected in Norway. Several Norwegian municipalities are experiencing growing pressure on forested land for development, being it new residential areas, industry, tourism, or new highways. The traditional mapping of cultural heritage, mainly based on chance discovery and inaccurate positioning, has proven inadequate for land use planning. Therefore, the Norwegian Directorate for Cultural Heritage, in cooperation with some counties and municipalities, are investing in the development of new methods, using new technology, for a more systematic mapping of cultural heritage. Grave mounds are one of the most frequent types of archaeological structure in Norway. We have earlier developed a method for the automatic detection of circular soil marks and crop marks in cereal fields in satellite and aerial images. Several of these detections have been confirmed to be leveled grave mounds. Methods based on optical images are of limited value in forested areas, since the archaeology tends to be obscured by the tree canopies. However, by using lidar data, the forest vegetation can be removed from the data, making it possible to detect archaeology in a semi-automatic fashion, provided the archaeology manifests itself as structures in the digital elevation model of the lidar ground returns, and that these structures may be described using some kind of pattern. In the majority of Norway’s 19 counties, there are intact grave mounds in forested areas. This means that a semi-automatic method for the detection of grave mounds in lidar data would be an important tool in a more systematic mapping of archaeology in Norway. The automatic method has been applied on lidar data from Larvik municipality in Vestfold County, Norway. Preliminary results are promising, and indicate that this may be a very useful tool for archaeologist in Norway for a more systematic mapping of cultural heritage.