The Digital Elevation Model (DEM) holds elevation values in a raster format dataset. The topography of the terrain is important to consider because it may influence (positively or negatively) the speed of travel over a given land cover depending on the travel scenario. This is especially true when patients are walking or using a bike to reach a health facility.
In AccessMod 5, the DEM is also used as the reference grid for each individual analysis and is therefore the layer that needs to be provided when creating a new project (see Section 5.3.2). The extent, projection and resolution of all the other layers to be imported in the project will be based on the DEM. It is therefore important to pay particular attention to this layer.
The DEM is not used when conducting isotropic analysis (i.e. no influence of slopes on speed of travel), but the DEM is mandatory in order to do an anisotropic analysis (i.e. when slopes affect the assumed speed of travel).