COGO

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COGO, an acronym for coordinate geometry, refers to a data conversion process in which a digital map is constructed from written descriptions, such as legal descriptions of land parcel boundaries. These descriptions often contain information about line length and direction, and point locations, all relative to the locations of certain key features such as geodetic control points, survey monuments, previously COGOed survey lines, etc.[1]

Some basic types of elements of COGO are points, spirals, lines and horizontal curves (circular arcs). More complex elements can be developed such as alignments or chains which are made up of a combination of points, curves or spirals.

When surveyors or civil engineers need to record the location of human-made features, such as land parcels, road centerlines, utility easements containing transmission lines, oil and gas leases, and so on, they typically provide the results on a survey plan that describes the location of features relative to each other. An example is a survey plan that diagrammatically shows a road centerline and the edge of the land properties adjoining the road. The road centerline and parcel boundaries comprise a number of straight and curved lines.

Each line has measurements that describe it. A straight line has a direction and distance, while a curved line has a radius, angle, arc length, direction, and so on. These measurements are coordinate geometry (COGO) descriptions. You can use these COGO descriptions to accurately re-create the features the surveyor captured. The survey plan also includes references to existing locations that help you to tie these new features into your GIS database. The reference could be the coordinates for a point or a measurement to a well known location such as a control point, a road intersection, or an existing parcel corner.[2]

COGO also refers to automated mapping software used in land surveying that calculates locations using distances and bearings from known reference points.[3]

COGO is also an acronym for the Coaltion of Geospatial Organizations, a consortium of organizations involved in geospatial data and policy issues.

COGO was originally a subsystem of MIT's Integrated Civil Engineering System (ICES), developed in the 1960s. Other ICES subsystems included STRUDL, BRIDGE, LEASE, PROJECT, ROADS and TRANSET, and the internal languages ICETRAN and CDL. Evolved versions of COGO are still widely used.

[edit] References

  1. NAIS Implementation Guide Glossary, Appendix C, Minnesota Governor's Council on Geographic Information, Accessed 21 April 2010
  2. An overview of COGO, ArcGIS Desktop 9.3 online help, Accessed 21 April 2010
  3. Wade, T. and Sommer, S. eds. A to Z GIS: An illustrated dictionary of geographic information systems, ESRI Press, 2006

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.

An example of COGO software is CCSURV. It can be downloaded from Professor Johnson's website at Purdue University, http://cobweb.ecn.purdue.edu/Geomatics/Course-Pages/CE200/

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