Land surface

From Wikipedia, the free encyclopedia

Land surface (ground surface) is the upper surface of the solid earth. It is formed by interchanging geological (migration of tectonic plates, faulting and faulting, volcanic eruptions), erosional (water and wind erosion, landslides) and extra-terrestrial (falls of meteors) processes and events. Land surface is, by its nature, fractal, anisotropic and non-periodic. This means that similar shapes and properties of land surface can be observed at various scales and in various directions. Land surface can be rather smooth but also very rough and dissected and complex. Areas of land surface that have relatively homogeneous morphometric properties are called landforms. Land surface is the object of study of geomorphology, geomorphometry, geology and similar geo sciences.

Land surface is commonly modelled either using vector (Triangulated Irregular Network or TIN) or gridded (Raster image) mathematical models. In the most applications in environmental sciences, land surface is represented and modelled using gridded models. In civil engineering and entertainment business, the most animated representations of land surface employ some variant of TIN models. In geostatistics, land surface is commonly modelled as a combination of the two signals - the smooth (spatially correlated) and the rough (noise) signal.

In practice, surveyors first sample heights in an area, then use these to produce a Digital Surface Model (also known as a digital elevation model). The DLSM can then be used to visualize terrain, drape remote sensing images, quantify ecological properties of a surface or extract land surface objects. Note that the contour data or any other sampled elevation datasets are not a DLSM. A DLSM implies that elevation is available continuously at each location in the study area, i.e. that the map represents a complete surface. Digital Land Surface Models should not be confused with Digital Surface Models, which can be surfaces of the canopy, buildings and similar objects. For example, in the case of surface models produces using the LIDAR technology, one can have several surfaces - starting from the top of the canopy to the actual solid earth. The difference between the two surface models can then be used to derive volumetric measures (height of trees etc).

Land surface parameters are quantitative measures of various morphometric properties of a surface. The most common examples are derivatives in different directions, which can the used to derive slope or aspect of a terrain or curvatures at each location. DLSM can also be used to derive hydrological parameters that reflect flow/erosion processes and climatic LSPs based on the modelling of solar radiation or air flow. Land surface objects are definite physical objects (lines, points, areas) that differ from the surrounding objects. The most typical examples are lines of watersheds, stream networks, ridges, break-lines, pools, borders of specific landforms etc. Each land surface object can also be quantified with various properties.

[edit] See also

Geomorphology; Geomorphometry; Landform; Geographic Information System;