Traditional ground based RTK surveys or even satellite or aerial data from manned aircrafts may not provide a dense enough surface of points to model 30 cm contours. For small contour intervals, a high-resolution topographic map must first be produced in order to model the contours. A topographic survey generally consists of many points (topo points) with horizontal and vertical coordinates (X, Y, and Z). While this may not sound overly difficult, that level of precision requires even more accuracy and a very dense topographic survey. This is generally sufficient for design, but many astute engineers prefer even more precision and target contour intervals of around 30 cm (1 foot).
#Ontour interval professional#
It is common for a professional topographic map of engineer-quality to have a contour interval of 50 cm (or about 2 feet in some parts of the world).
Therefore, precise topographic maps are frequently produced by collecting data in the field, often by a licensed professional land surveyor or civil engineer. Large contour intervals do not give detail as to where low spots that may accumulate water are or where slopes may be unstable and could lead to landslides. Having an elevation off by 40 m at a single point could mean the difference between several tons of material that needs to be moved or it could even mean a location is not suitable to build upon. When it comes to civil engineering projects such as road or bridge construction, hydrologic modeling, construction site preparation, or other design projects, 40 meters is no where near precise enough of a contour interval. This means that the change in elevation between one contour line and the next is 40 m up or down. 1:24 000), contour map of many tens of square kilometers or miles might have a contour interval of 40 m. For example, a course, or large-scale (e.g.
When topographic maps are generated and contours created the spacing between neighboring contour lines is defined as the contour interval. When it comes to topographic mapping, unmanned aerial vehicles (UAVs) have filled an efficiency gap in the geospatial toolbox between when it makes the most sense to use terrestrial methods such as RTK GNSS, total stations, and laser scanners, and when it makes sense to hire a manned aerial mapping service or order satellite imagery for a project. These contours are used to calculate metrics such as slope, water flow, cost estimates, cut and fill (dirt to be moved from where to where), locations of undulations or hazards in the existing surface, and volumes of material. Just about any project design requires a topographic survey in order for a project manager to know what the characteristics of the ground are in order to properly design the project.Ī topographic map is most often delivered as contours which are 2D isolines that depict the 3D shape of the Earth’s surface at a given location. Topographic mapping is a routine task for many surveyors, engineers, and construction professionals.
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