02/17/2026
The Earth is flat. Well, not really, but it would surely make survey measurements easier. Surveying instruments like steel measuring tapes, electronic distance meters, and telescopic instruments are all based on line of sight, meaning a straight line. So, how do we compensate for the fact that the Earth is a curved surface?
Geodetic models of the Earth, called geoids or ellipsoids can estimate the curved distances along the surface of the Earth, but the calculations are rigorous. Surveyors have developed low distortion projections that assume, with little error that the surface of the Earth is flat. This systematic approach allows the use of simpler survey measurement that can be converted to the actual curved surface through computer calculations.
We have probably all seen projections in school, where a map of the world hangs on the wall. The map is a mathematical transformation that converts the Earth’s surface into a two dimensional plane. Common types of transformations include conical, cylindrical, and planar. While a two dimensional map of such a large surface may be convenient for illustration, it introduces large distortions of the distances and sizes. However, if we limit our measurements to a much smaller portion the distortion is less severe.
Here is an example. Suppose we were to lay out and measure a straight line of one mile in length. On the ground the measurement would be 5,280.00 feet or exactly one mile. On the geodetic surface that follows the Earth’s curvature the distance becomes 5,280.07 feet or a little less that one inch more than a mile. Finally in the low distortion projection, that is, assuming the measurement is on a flat surface, the distance becomes 5,280.01 feet and makes a very small error.
So, a low distortion projection can simplify survey measurements while retaining the ability to calculate the relative position on the Earth or the geographic location. And although the numerical methods are sophisticated it eventually makes mapping of property more congruent in the overall map relationship.