A topographical survey is an assessment to determine the configuration of the earth’s surface. It generally concerns the relief of the earth (or moon, planet or asteroid), which can also include artificial and natural feature such as hills, valley, depressions, streams, bridges and buildings. The recording of terrain involves determining the terrestrial or three-dimensional space position of points and the distances and angles between them. A graphic representation of the relief of an area is called a topographic map, which will be constructed from data which shows the vertical and horizontal locations plotted in the survey. A 3D representation of the topographical survey can be created, called digital surface models, which are with objects such as plants or buildings, or digital terrain models, which are without.
A topographical survey is a form of land surveying which measures the elevation of plots on a particular piece of land, which are then presented as contour lines on a plot. A direct topographical survey will accurately determine the relief using the positions of certain points, and find the distances and angles between them. This is done using levelling instruments such as astheodolites, dumpy levels and clinometers. Direct surveys such as these can be manual or GIS-based, the latter being a computerised system used to capture, store, manipulate, analyse, manage and present the findings of the topographical survey.
A topographical survey may be conducted for a number of reasons. The plotting of points in a horizontal coordinate system such as latitude, longitude and altitude may be commissioned by architects or engineers before building or installing drainage Topographical surveys are also carried out for other reasons such as archaeological digs, military planning and geological exploration and mapping.
There are other types of topological survey than a direct survey. Some studies are carried out at a distance from the subject area, called remote sensing. Aerial and satellite imagery are a part of geovisualisation. Aerial and satellite imagery use a non-visual spectra of light to determine the lie of the land, showing vegetation and other land use information in a more detailed way. Photogammetry can be used to create surveys of a 3D surface by using a number of photographic images taken from different positions, usually from different passes of an aerial flight.
Radar and sonar are used to generate Digital Elevation Models. Sonar maps which determine the terrain of the ocean floor are an example of these topographical surveys in use. A light detection remote sensing technique is another method being used in topography, which uses a laser instead of radio waves.
Topography is also used in medical practice, for brain mapping, measuring the curvature of conea, and superficial human anatomy. It is also used in mathematics when measuring the variables in a map or space.
SUMO Surveying Services are a multi-disciplinary survey business committed to maintaining the highest standards in all aspects of surveying. SUMO’s services include topographical surveys, as well as utility detection, utility mapping and measured building surveys.