Digital Elevation Model

There exists many different resolutions for DEM datasets, ranging from 30 m to 1 km. GTOPO30 with 1 km resolution DEM is used in this work. It has a horizontal grid spacing of 3000 (corresponding approximately to 1 km) and vertical units represent elevation in meters above mean sea level. It covers latitudes from 90◦ north to 90◦ south, and longitudes between 180◦ west to 180◦ east. The DEM data set has 33 smaller pieces, or tiles in GEOTIFF format.