Abstract
Topographic data obtained by airplane-based surveys is spatially disordered. There are both high and low density portions in the topographic data, and some data are redundant. A graphical terrain model or a digital elevation model (DEM) is generally generated from raster data, and the decimation (reducing the level of redundancy in data) is based on that data structure. However, this approach is not useful when rasterizing topographic data derived from laser range finders because imposing a raster data structure introduces visual and numerical errors. In this research, topographic data was obtained using a one-axis laser range finder mounted on an unmanned helicopter. The collected data were not evenly spaced over a regular grid as rasterized data are. This paper describes methods that can automatically generate triangular mesh from a topographic data set, and simplify the data while maintaining accuracy. These methods were evaluated by examining the topographical feature error resulting from simplifying the 507 raw data points obtained by the helicopter-based survey. When a data set of 107 points were generated (79% size of the original raw data), topographical error was less than 0.12 m. By way of comparison, when 400 data points were eliminated at random, the corresponding error was 1.35 m. Furthermore, when 110 points data were generated by rasterizing, the error was 0.88 m. Consequently, it was concluded that the developed method was very effective.
