A digital surface model (DSM) is a topographic elevation model of the Earth surface that provides a geometrically highly accurate representation for the purpose of overlaying the model with a wide range of GIS data. DSM provides a surface elevation of every natural and artificial feature visible within the image area. DSM forms the basis for creating true orthophoto production and 3D models.

A digital elevation model (DEM) is a representation of ground surface topography. It is usually generated using remote sensing techniques, but is also commonly created using land surveying. The DEM is an extraction of the DSM with all elevations not representing ground surface (bare earth) removed. The DEM data is used to create a terrain surface, terrain orthorectification and contour depiction. AutoCAD and AutoCAD Land Desktop are the most common applications used to read the DEM. In AutoCAD Land Desktop, the user can generate contours.

A digital terrain model (DTM) is created using the DEM and the addition of breaklines or higher density points that define adequately all natural and artificial changes in surface slopes. A DTM enables the generation of contours to reflect actual terrain surfaces and to render computerized 3D terrain visualization techniques.

First Base Solutions has an inventory of DTM that has been divided into tiles and is provided in DWG format with 3D polylines. The capture of the topographic model of the surface includes elevations on a 40 m to 50 m grid spacing with an accuracy of +/- 40 cm. Breaklines were added along visible terrain impacting features such as the edge of roads, drainage and centerline of railways. Some of the areas available from our 2002 dataset include Niagara, Hamilton, Halton, Peel, Toronto, York, Durham, Simcoe and Kawartha.

To browse our selection of DTM datasets, visit our MapWarehouse.

Custom topographic mapping is also available through our mapping team.