Editing Topography (section)

===Field survey===
[[File:Vermessungspunkt.jpg|thumb|upright=0.7|right|A surveying point in [[Germany]]]]
{{Further|Surveying|Geodesy}}

Surveying helps determine accurately the terrestrial or [[three-dimensional space]] position of points and the distances and [[angle]]s between them using [[leveling instrument]]s such as [[theodolite]]s, [[dumpy level]]s and [[clinometer]]s.
[[GPS]] and other [[global navigation satellite systems]] (GNSS) are also used.

Work on one of the first topographic maps was begun in France by [[Giovanni Domenico Cassini]], the great Italian astronomer.

Even though remote sensing has greatly sped up the process of gathering information, and has allowed greater accuracy control over long distances, the direct survey still provides the basic control points and framework for all topographic work, whether manual or [[GIS]]-based.

In areas where there has been an extensive direct survey and mapping program (most of Europe and the Continental U.S., for example), the compiled data forms the basis of basic digital elevation datasets such as [[USGS DEM]] data. This data must often be "cleaned" to eliminate discrepancies between surveys, but it still forms a valuable set of information for large-scale analysis.

The original American [[Topographical surveys|topographic surveys]] (or the British "Ordnance" surveys) involved not only recording of relief, but identification of landmark features and vegetative land cover.