Topographic surveying consists of representing the surface - planimetric and/or altimetric - on a map or plan of notable points or geographical features, as well as other relief, vegetation or construction details, by means of high-precision georeferenced measurements, using various equipment such as: Optical Total Stations (manual or robotic, GNSS (commonly known as GPS), 3D Laser Scanner's, UAV/Drones, among other sensors, tools and software for calculation, adjustment, drawing or 3D or BIM modelling.
They are usually carried out by a professional in the area of geographical sciences and are a fundamental element, which is present in the various phases of a project, whether in the initial phase as a basis for the study of the project to come, or in the execution, verification, supervision of the work and the representation of the final canvas of the completed project.
The scales used vary depending on the detail required, which usually range from 1/200, 1/500, 1/1000, 1/2000, 1/5000 and very occasionally 1/10000. From this last scale onwards we enter the field of Cartography, for representations of regional or national scope.
There are three types of topographic survey:
- Planimetric - surveying measurements on a plane: X,Y;
- Altimetric - when the vertical coordinates of the place are added: Z;
- Plani-altimetric - union of the two previous types, it allows a more complete mapping with three-dimensional information.
What does a topographic survey usually contain?
- Geographic or geodetic coordinates are of a curvilinear character and are therefore given in degree, minute and second, known as latitude and longitude or plane coordinates are those which are projected from the curved medium (ellipsoid) onto the cartographic plane chosen as a function of the location on the earth's surface and objective;
- Indication of cartographic and/or geographical north;
- Land boundaries (walls, fences, property marks, etc.);
- Heights and contour lines showing the relief/morphology of the terrain;
- Location of buildings and respective elevations, eaves and ridge points;
- Location of infrastructures (water, sanitation, storm water, electricity, telephones, gas, etc.) and respective thresholds;
- Location of accesses (roads, paths, tracks, etc.);
- Location of landscape elements and main tree species (especially if they are protected species).
