Topographical Survey Services

Topographical survey involves the generation of contours and the production of Digital Terrain Models. Such services are required by engineers and designers to help calculate volume for earthworks (cut and fill). With the advent of computer technology most of our want data digital format, usually ASCII and MOSS

Topographic Surveys are used to identify and map the contours of the ground and existing features on the surface of the earth or slightly above or below the earth’s surface (i.e. trees, buildings, streets, walkways, manholes, utility poles, retaining walls, etc.). If the purpose of the survey is to serve as a base map for the design of a residence or building of some type, or design a road or driveway, it may be necessary to show perimeter boundary lines and the lines of easements on or crossing the property being surveyed, in order for a designer to accurately show zoning and other agency required setbacks.

Topographic Surveys require “bench marks” to which ground contours are related, information regarding surface and underground utilities, determination of required setbacks, etc.

Topographical Survey

Definitions

Topography
The shape, configuration, relief, roughness, or three-dimensional characteristics of the earth’s surface.

Topographic Maps
Show topography together with natural and artificial features such as streams, lakes, buildings, highways, etc.

Topographic Surveys
Surveys made to determine the configuration of the earthÆs surface and to locate natural and cultural features on it.

Uses of Topographic Maps
Topographic maps are used by a variety of professions from engineers, architects, foresters, geologists, etc.
The most common use of topographic maps is in the planning stages of projects to help design the layout and location of buildings, roads, dams, pipelines, landscapes, fire control routes, trails, etc.

Methods For Topographic Surveying

Aerial (photogrammetric)
Using aerial photographs to determine distances, elevations, areas, etc for topographic mapping.

Transit-Stadia
Distance, elevation, and location measurements are taken in the field, recorded in the field book, and then plotted on paper in the office.

Plane Table
Similar to transit-stadia method except that the data is plotted in the field on paper attached to a drawing board mounted on a tripod (plane table).

Controls

Topographic surveys require good controls. Types of controls:

  1. Horizontal
  2. Vertical

The controls are used for the basis of the topographic survey measurements. An error in the control will be reflected in errors in the position and/or elevation of the topography.

Horizontal Control

  • Is provided by two or more points on the ground and precisely fixed in position by distance and direction.
  • Is the basis for map scale and locating topographic features.
  • For small areas, horizontal control for topographic work is usually established by a traverse, but sometimes a single straight line may be used.

Vertical Control

  • Is provided by bench marks in or near the tract to be surveyed.
  • Is the foundation for correctly portraying relief and elevation on a map.
  • Vertical controls are usually established by lines of levels starting and closing on bench marks.
  • A surface of a body of water is a continuous bench mark and may sometimes be used as a vertical control.

Locating Details In The Field

The most common methods used to locate a point in the field are:

  • One angle and the adjacent distance
  • Two distances
  • Two angles
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