DEMs represent which type of elevations?

Digital Elevation Models (DEMs) represent elevations above the "bare earth" surface, meaning they illustrate the ground's topography without any structures, vegetation, or other objects that can obscure the true altitude of the terrain. This is crucial because DEMs aim to provide a clear representation of the terrain's changes, which is essential for various applications in GIS, such as hydrology, land use planning, and environmental analysis.

The concept of "bare earth" specifically indicates that the elevation values in DEMs are based on the natural surface of the terrain, offering an accurate foundation for analyzing landform characteristics. In this context, understanding the topography allows for effective modeling and analysis of geological phenomena, ecosystem dynamics, and more.

Other choices such as Mean Sea Level refer to a reference point rather than a depiction of the earth's surface; Lowest Point denotes specific features rather than a comprehensive model; and Average Terrain could imply a mixed representation that doesn’t convey the precise elevations that DEMs provide. Therefore, emphasizing the "bare earth" aspect links directly to the primary purpose of DEMs in visualizing and analyzing topography.