THE STUDY OF MOBILE LASER SCANNING DATA ADJUSTMENT RESULTS FOR LARGE SCALE TOPOGRAPHIC MAPPING
Keywords: Mobile laser scanning, Large scale topographic mapping, Adjustment, Accuracy estimation, Control points, GNSS signal
Abstract. Mobile laser scanning (MLS) data are widely used for solving various tasks. To be sure that these data are appropriate for a specific task it is necessary to adjust data with a certain accuracy. Large scale topographic mapping is one from the tasks often solved by MLS data. Necessary accuracy of creating topographic plans is determined with a requirements document. Topographic plans are always created in a certain coordinate system. For this reason, MLS data should be previously transformed in the required one. For transformation control points measured with other more accurate methods should be applied. The quantity of necessary control points depends on a surveying area. For urban areas a lot of control points are required due to bad quality of GNSS signal. Much research has been conducted for these areas. For areas with open view of the sky it is required significantly fewer control points. Moreover, there are not so many vertical objects in areas with open view of the sky. Large errors can take place in the result of automatic adjustment of point cloud’s multi-passes. The results of both relative and absolute MLS data adjustment are given for the area with a good GNSS signal. The paper presents the results of accuracy estimation with different quantity of control points. The main goal of the paper is to determine the minimum number of control points for MLS data to be appropriate for creating topographic plans at a scale of 1:500 with a contour interval of 0.25 m.