Forms of topographic data Topography

1 forms of topographic data

1.1 raw survey data
1.2 remote sensing data
1.3 topographic mapping
1.4 digital elevation modeling
1.5 topological modeling

forms of topographic data

terrain commonly modelled either using vector (triangulated irregular network or tin) or gridded (raster image) mathematical models. in applications in environmental sciences, land surface represented , modelled using gridded models. in civil engineering , entertainment businesses, representations of land surface employ variant of tin models. in geostatistics, land surface commonly modelled combination of 2 signals – smooth (spatially correlated) , rough (noise) signal.

in practice, surveyors first sample heights in area, use these produce digital land surface model in form of tin. dlsm can used visualize terrain, drape remote sensing images, quantify ecological properties of surface or extract land surface objects. note contour data or other sampled elevation datasets not dlsm. dlsm implies elevation available continuously @ each location in study area, i.e. map represents complete surface. digital land surface models should not confused digital surface models, can surfaces of canopy, buildings , similar objects. example, in case of surface models produces using lidar technology, 1 can have several surfaces – starting top of canopy actual solid earth. difference between 2 surface models can used derive volumetric measures (height of trees etc.).

raw survey data

topographic survey information historically based upon notes of surveyors. may derive naming , cultural information other local sources (for example, boundary delineation may derived local cadastral mapping). while of historical interest, these field notes inherently include errors , contradictions later stages in map production resolve.

remote sensing data

as field notes, remote sensing data (aerial , satellite photography, example), raw , uninterpreted. may contain holes (due cloud cover example) or inconsistencies (due timing of specific image captures). modern topographic mapping includes large component of remotely sensed data in compilation process.

topographic mapping


a map of europe using elevation modeling

in contemporary definition, topographic mapping shows relief. in united states, usgs topographic maps show relief using contour lines. usgs calls maps based on topographic surveys, without contours, planimetric maps.

these maps show not contours, significant streams or other bodies of water, forest cover, built-up areas or individual buildings (depending on scale), , other features , points of interest.

while not officially topographic maps, national surveys of other nations share many of same features, , called topographic maps.

existing topographic survey maps, because of comprehensive , encyclopedic coverage, form basis derived topographic work. digital elevation models, example, have been created not new remote sensing data existing paper topographic maps. many government , private publishers use artwork (especially contour lines) existing topographic map sheets basis own specialized or updated topographic maps.

topographic mapping should not confused geologic mapping. latter concerned underlying structures , processes surface, rather identifiable surface features.

digital elevation modeling


relief map: sierra nevada mountains, spain



3d rendering of dem used topography of mars

the digital elevation model (dem) raster-based digital dataset of topography (hypsometry and/or bathymetry) of or part of earth (or telluric planet). pixels of dataset each assigned elevation value, , header portion of dataset defines area of coverage, units each pixel covers, , units of elevation (and zero-point). dems may derived existing paper maps , survey data, or may generated new satellite or other remotely sensed radar or sonar data.

topological modeling

a geographic information system (gis) can recognize , analyze spatial relationships exist within digitally stored spatial data. these topological relationships allow complex spatial modelling , analysis performed. topological relationships between geometric entities traditionally include adjacency (what adjoins what), containment (what encloses what), , proximity (how close something else).

reconstitute sight in synthesized images of ground,
determine trajectory of overflight of ground,
calculate surfaces or volumes,
trace topographic profiles,




^ see example publications of national geographic trails illustrated maps , delorme products.