PROTOTYPE OF NATIONAL DIGITAL ELEVATION MODEL IN INDONESIA
Although medium scale mapping has been done for the entire territory of Indonesia, there has never been a DEM unification to produce seamless national DEM. The main problem to generate national DEM is multi-data-sources. Each of them has their own specification, so unification of data becomes not easy to do. This research aims to generate global DEM database in Indonesia. Because its coverage covers only one country, it is called National DEM. This study will be focused on the northern part of Sumatra island, precisely in the boundaries between Aceh and North Sumatra province. The principle method in this study was to rebuild DEM data by considering the height difference between ground elevation from masspoints and surface elevation from DSM. By setting up a certain threshold value, the filtering process was then performed. The output was generated by gridding process. Validation in this research was done by two methods: visual inspection dan statistical analysis. From visual inspection, the National DEM data becomes smoother than the input data, the reality of the data is maintained, and still shows the landscape of the DSM input. From statistical analysis, compared with 142 GCPs, it is obtained that Root Mean Square Error is 2.237 m, and vertical accuracy based on Indonesian Mapping Accuracy Standard is 3.679 m. The result is good for medium scale base map and, based on the standards in Indonesia, the data can be used for 1 : 25,000 scale mapping.