Maastamalli

Maastamalli is a representation of the Earth's surface used in geography, cartography, civil engineering and environmental modeling to analyze terrain and surface processes. It focuses on relief and elevation, and can be used to simulate water flow, slope, and terrain accessibility. Depending on context, a maastamalli may emphasize bare ground or include surface objects such as vegetation and buildings.

There are several forms of maastamalli. A digital terrain model (DTM) or digital elevation model (DEM) depicts the bare earth surface, removing vegetation and man-made structures. A digital surface model (DSM) includes objects on the surface, such as trees and buildings. A terrain model can also be represented as a triangulated irregular network (TIN) for irregularly spaced data. In practice, DEM is often used as a general term for gridded elevation data, while DTMs stress the absence of elevated objects.

Data sources for maastamallit include airborne and terrestrial LiDAR, photogrammetry from stereo imagery, radar interferometry, and multi-view satellite imagery. Data are processed through filtering and interpolation to produce a grid or mesh at a chosen resolution. The vertical datum and the coordinate reference system determine accuracy and interoperability with other geospatial datasets.

Applications of maastamallit span hydrological modeling, flood risk assessment, slope stability analysis, urban planning, transportation engineering, forestry, and environmental studies. They enable simulations of water flow, soil erosion, landform change, and line-of-sight or accessibility analyses. Limitations include data gaps, occlusion by vegetation or buildings, and errors arising from sensor noise and interpolation.

See also: Digital elevation model, Digital terrain model, Digital surface model, LiDAR, Geographic information system.