Monitoring of Cable Corridors and Anchor Tree Dimensions In Cable Yarding Using Personal Laser Scanning

Cable yarding is one of the most relevant technologies that enables efficient and sustainable use of timber resources in mountainous areas. A traditional standing skyline setup in uphill operation with a tower yarder includes at least a skyline, a mainline and guylines with corresponding anchor trees. The planning for this setup is commonly done in advance based on crew experience and can be supported by using smart tools integrated into geographic information system. In practice, the actual exact location of the tower yarder, the rope configurations and the position of the anchors are usually different compared to the planning situation. Exact cable corridor layouts as well as the dimensions of the anchor trees of cable yarding systems are difficult to record and are usually not documented.

The goal of this study was to automatically detect and measure the courses of the skylines and guylines of cable yarding systems using a mobile personal laser scanner (PLS). The cable corridors were selected in such a way that a broad variation in forest type (broadleaved, coniferous, and mixed), forest structure (one- or two layered) and silvicultural treatment was represented. The point clouds captured with a GeoSLAM ZEB Horizon (GeoSLAM Ltd. Nottingham, UK) personal laser scanner were classified, clustered and segmented in order to analyze the skyline and guylines independently of the rest of the 3D environment (terrain, trees, other vegetation, etc.). Region growing algorithms were used to segment and trace the cable corridor in the 3D point clouds. By tracking the guy lines, the anchor trees of the cable yarding system can also be automatically detected and measured (tree position, dbh, height). Subsequently, the geometries (corridor length, rope angle, mounting position of supports, skyline deflection) of the system can be reconstructed and documented on the basis of this data. A precise digital representation of the real cable yarding corridor configuration is created (digital twin). Manual segmentation of the cable corridors and manual measurements of the anchor trees served as reference data.

This study shows that such systems can provide important digital information for the planning, operation, supervision and documentation of timber extraction and serves as input data for more precise planning of future cable yarding operations.