INTERACTIVE EXTRACTION OF LINEAR STRUCTURES FROM LIDAR RAWDATA FOR ARCHAEOMORPHOLOGICAL STRUCTURE PROSPECTION

A new detection and visualization tool to inspect raw LiDAR data for archaeological prospection is introduced in this paper. It allows the supervised extraction of linear structures (ridge or hollow) from the 3D ground points, for on-line detailed analysis of their cross and longitudinal profiles. Using raw data provides a richer information than an interpolated digital terrain model. In particular, the extraction process is made aware of point repartition irregularities caused by dense canopies in forested environments. The tool is based on a recent curvilinear structure extraction framework with fast execution time, that ensures a good interaction. Additional performance is achieved through the detection of the local terrain trend around the structure, that allows finer characterizations of the extracted structure. The suitability to several application purposes has been evaluated by archaeologists through real context experiments. The tool was first applied to the survey of a well-known medieval wall and to the identification of its less preserved parts, that are still undisclosed in the forested landscape. Then it was used in the scope of a prospective work about man impacts on its environment to detect and analyze old holloways and to get a better understanding of their local sunkness or the cause of their local deviations. Potential and limits of the tools are discussed. Open source and executable codes are left available for more extensive exploitation and possible integration into GIS softwares.