Why is my “80 Acres” really only 79 acres?
When the original government surveyors began the task of laying out (surveying) the public lands of Oklahoma, one of their instructions was to make each section as close to 640 acres as possible. excerpt from the BLM manual of Survey Instructions Chapter 1-21. The basic provisions require that the public lands "shall be divided by north and south lines run according to the true meridian, and by others crossing them at right angles, so as to form townships six miles square;" that "the townships shall be subdivided into sections, containing as nearly as may be, six hundred and forty acres each;" and that "the excess or deficiency shall be specially noted, and added to or deducted from the western and northern ranges of sections or half-sections in such townships, according as the error may be in running the lines from east to west, or from south to north." The system of rectangular surveys fits the basic requirements to the curved surface of the globe.