FAQ: What is the Carter coordinate system?

Contact: Brandon C. Nuttall
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Key to Carter coordinate section, letter, and numbering patternsThe Carter coordinate system is a land grid, based on latitude and longitude, used to locate oil and gas well data in Kentucky. The system was developed by the Carter Oil Company to mimic the township and range location system in areas that had not been surveyed. The State is divided into a regular grid with each cell (or "quad") being five minutes of latitude by five minutes of longitude. These quads are assigned letters (equivalent of the township) beginning with "A" in the south and increasing through "Z" and "AA" to "GG" northward. The quads are assigned numbers (equivalent of the range) beginning with zero (0) in the west and increasing to 92 in the east. Each five-minute by five-minute quad is further subdivided into 25 one-minute by one-minute sections. Within the one-minute section, the location is pinpointed by specifying the distance from an adjacent pair of one-minute section boundaries to the well. The Carter coordinate is written by specifying a pair of footages from the one-minute section boundaries and the reference boundary (north, south, east, or west) for each, the one-minute section number, the five-minute quad letter, and the five-minute quad number. A Carter coordinate and topographic index map of Kentucky is available by request, contact the Public Information Center (Publication Sales).

A Carter coordinate location is defined only for the North American Datum of 1927 (NAD27). If you use the KGS Coordinate Conversion Tool to convert a NAD83 location to a Carter coordinate, the output will be NAD27 only.

I have a Carter Coordinate and want to convert it to latitude and longitude.

  1. Use the Kentucky Geological Survey coordinate conversion tool web site. To use the tool, in the Select a Projection dialog, set the value to "KY Carter Coordinates." Fill out the Carter coordinate dialog boxes and click the convert coordinates button. The location will be converted to a variety coordinate systems in both NAD27 and NAD83.
  2. Use the Carter coordinate conversion software available by following the link below. The sample program provides geographic coordinates in decimal degrees of latitude and longitude, NAD27.This algorithm is based on a lookup table to determine the number of feet per minute of latitude and longitude at a particular latitude. It may differ slightly from locations calculated with the KGS Coordinate Conversion Tool which uses a direct calculation of that footage value. It is recommended that you download and install the KYGeoTools ActiveX component.
  3. Use the oil and gas well data search pages to find the well(s) and download the data ("header data") to a file. Several output coordinate systems may be chosen including decimal degrees (NAD27 or NAD83), State Plane (feet), or UTM (meters).
  4. If you have programming experience you can implement the conversion routines in a spreadsheet or database program. Download the distribution file. Open the carterll.pas file with a text editor and look for the function _CCToLatLon.


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Created 18-Jul-2002