Objekttolkning i laserdata : En undersökning av möjligheten att ersätta eller komplettera ortofoton i topografisk kartering

Today, the rate of topographic map production is limited by the acquisition rate of orthophotos. To increase the rate at which topographic maps can be supplied, the production rate of orthophotos needs to be improved. An alternative is to utilse other acquisition methods for topographic map production, such as LiDAR. To assess whether,and to what extent LiDAR can substitute, complement, and enhance orthophotos, various data layers are derived. The layers are LiDAR intensity, traditional monodirectional hillshade, multidirectional hillshade, slope and a composite layer. Five object types have been selected to examine the interpretability across the orthophoto and LiDAR-derived layers. The object types are minor road, tractor path, foot path, turnaround point and watercourse. For these object types, 3, 2, 2, 5 and 1 objects were selected, respectively. For the minor road, tractor path, foot path, and watercourse objects, line representations were created from the interpreted extent of the features. The interpretation of each object, across all layers, wasmeasured by two values: one statistical discrepancy value, CE90 and one evaluation grade assessing the visual interpretability of an object.The results indicate that orthophotos are superior in field terrain, however, intensity and composite are good alternatives for interpretation. In forest terrain, intensity is the most potent, but in dense forests, the two hillshades and slope layers provide better interpretability. In irregular terrain, the interpretability is mostly like other terrain types for thetwo hillshades and slope layers. The CE90 discrepancies are all within the positional accuracy specified for all objects that were interpreted. This study concludes that LiDARdata could substitute orthophotos, even though some limitations are present; that lidar can be an important complement to orthophotos, especially in forest and shaded areas; and that the combination of orthophoto and LiDAR tried in this project, is not the most efficient layersin any application. Alternating between layers may therefore be a more sensible approach.