A .dem file is a Digital Elevation Model (DEM) file, a raster-based geospatial data format used to represent terrain elevation. It stores elevation values for a regular grid of locations, providing a digital representation of the Earth's surface or other planetary surfaces. These files are crucial for various applications, including topographic mapping, hydrological modeling, landscape visualization, and geographic information systems (GIS). DEMs are often created from remote sensing data, such as satellite imagery or LiDAR, or from digitized topographic maps. The elevation values within the .dem file can be used to derive other terrain attributes, such as slope, aspect, and curvature. The format typically includes a header containing metadata about the data, such as the coordinate system, cell size, and data type. The data itself is usually stored as a grid of elevation values, with each value representing the elevation at a specific location. Different DEM formats exist, each with its own specific structure and encoding methods. The USGS DEM format is a common example.