What is a Digital Elevation Model (DEM)?
A Digital Elevation Model is a representation of the earth’s surface for a geographic area stored in a digital file containing regularly spaced point locations with an elevation attribute. The United States Geological Survey (USGS) DEM is a specific data product which adheres to standards defined by the National Spatial Data Infrastructure. USGS DEMs can be downloaded for use in the ArcView Spatial Analyst.
Digital elevation models (DEMs) are collections of elevation points for an area. Among other things, certain software can display DEMs to show the terrain surface in three dimensions and from a choice of viewpoints. DEMs are created by collecting elevations and referencing them to corresponding points in the mapped area. The elevations add a Z value to the ground’s X and Y horizontal coordinates. A systematic grid pattern or a stratified method of data collection is used to gather elevation coordinates. These two methods are often referred to as regular and irregular grids respectively. A regular grid has points equally spaced regardless of the shape of the terrain. An irregular grid samples extra points or a larger percentage of points in areas of increased relief variation, such as along ridges, mountains, and valleys. The spacing and density of the elevations points directly effects the accuracy of a DEM. The higher the density of elevation points recorded results in the model’s dep
A Digital Elevation Model (DEM) is digital cartographic/geographic data in raster form. The terrain elevations for ground positions are sampled at regularly spaced horizontal intervals. DEMs are derived from hypsographic data (contour lines) and/or photogrammetric methods using USGS 7.5-minute, 15-minute, 2-arc-second (30- by 60-minute), and 1-degree (1:250,000-scale) topographic quadrangle maps.
