Problems can also arise when a parcel is divided using assumed dimensions which prove to be incorrect. For example, a forty is, in theory, a square forty acres measuring 1,320 feet on each side. In fact, a forty in theory is not the same as where the forty was actually laid out by the original government survey. The section corners actually laid out by the original government survey were never precisely located where they were theoretically supposed to be. Legally, the actual corners are where they were actually laid out, not where they might have been laid out using more precise survey technique that was unavailable at the time of the original survey.
Some forties are considerably smaller or larger than forty acres.
Another common description error occurs whenever a parcel is described using a measurement from a waterway. Because waters rise or fall, and shorelines erode, measurements from a waterway are a moving target and imprecise. Measurements should never be taken from a waterway because of that problem. These errors are just a sample of description problems. Many others also arise from time to time.