Vertical Assessment of Public Global Digital Elevation Models Including 1"SRTM Generally, and in Eight Sample Land Covers and Terrains of Tanzania
Recent public global digital elevation models (GDEMs) include, , and . GDEMs have many useful applications in many areas. Many developing countries are not in position to determine their own reliable digital elevation models (GDEMs). Often a resort is to search for public GDEM that suits its purpose better. The search for a suitable DEM for Tanzania has been going on for more than a decade. In this paper, a review of search for a better GDEM for Tanzania in the past five years through vertical assessment of public GDEMs is given. The method used is the statistical assessment of the differences of GDEM and GPS control point heights relative to EGM96 geoid model. The assessment used between 127 and 222 GPS control points scattered over Tanzania. Always two GDEMs were compared and validated, often was one of the GDEMs. In 2012 and 2013, the comparison and assessment was general over the whole country. In 2014, in addition to the general assessment, three representative land covers and terrains were also involved. In 2015, the representative land covers and terrains were increased to six and in 2016 they were eight. The other public GDEMs involved are , and. and proved in their first assessments to be much inferior to and . The overall fit of to the GPS controls is about 7m while for the and is around 10m. is close to the two 3-arc seconds GDEMs by about 6m.
Performance of is the best in flat and almost bare land where STD is 1.5m and RMS is 2.4m, and is the worst in rough, mountainous and forested terrain where the STD is 10m and RMS is 10.5m. performance is superior to all the GDEMs validated until 2016 and therefore the best DEM for Tanzania.
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