Build 3D Urban Model for Noise Mapping

GIS(Geographic Information System) data is widely used as basic data for building noise maps. However, GIS is usually written in 2-Dimension because it is primarily aimed at storing information in the form of an object. In the case of noise mapping, the road model, especially in 3-Dimension, can contribute to accurate noise prediction. In this study, airborne LiDAR(Laser Detection and Ranging) was used to build precise 3D road. LiDAR can be used to construct a 3D road, but if the road crosses vertically, such as the Spaghetti Junction, the exact height of the road can not be calculated for the road passing downward. In order to solve this problem, we used a method to detect the actual height and other vertices and to correct by weighting the distance according to the vertex height immediately before and after the vertex. Nevertheless, this method could not be applied in case of start point and end point, or if vertices other than the actual height exist in succession. Especially, this situation occurred frequently on local road. This happens because the local road often covers trees. Therefore, in order to exclude the influence of the height of the tree, estimating the original altitude by searching the altitude around a certain range of the vertex. By this method we could obtain a more accurate 3D road.