A topographic survey, or topo survey, is used to define the surface of the earth on a three dimensional plane.
Topographic surveys can be provided for the following purposes:
- To determine the difference in elevation between two or more points
- House, well and septic design
- Road or driveway design
- Drainage design
- Flood plain certifications
- Building and improvement placement
- Volume calculations for liquid, solid or gas
- Landscaping design and planning
- Environmental studies
- Ground control for Ariel surveys
- Utility crossings
- General estate planning
Some things you should know about topographic surveys:
Datum is any level surface, line or point used as a reference in measuring elevations. The datum of your topographic survey can vary based on the intended use. Examples would be: assumed, approximate U.S.G.S., U.S.G.S., NGVD29, NAD87, ect... It really depends on where you are and what you are planning to do.
Contour Line is a line joining points of equal elevation on a surface and the representation of said line on a topographic map.
Contour Interval is the difference in elevation represented by each contour line. A common U.S.G.S. topo map, for example, shows a ten foot contour interval (one contour line for every ten feet in elevation change). For field or flight topography the most common contour interval is two foot. This is usually adequate for well and septic design.
Spot Elevation is an elevation of a point on a map, usually indicated by a dot with an elevation relative to the reference datum.
Benchmark is a defined point (either set or described) of known elevation from which other elevations may be established.
Flight topography is when the contours and other details are developed by a photogrammetrist who flies over the property and photographs it in a stereo view. The ground control survey is provided by the land surveyor. Scale and detail are limited with flight topography and can be enhanced with a ground field survey. An area where the ground is obscured (under pine trees) is usually not contoured by the flight company.
Samples of my topographic surveys can be found here: legendlandsurveying.com/page12.php