I remember 30 years ago working on ESRI’s COGO software. If you ever used it back in the day, you were a hero creating a landbase from scratch with only measurements from tract and parcel maps and making sure everything closed well with your traverses.

One thing I found interesting was there were two definitions for measuring 1 foot. There was the international foot, which was defined as 1 inch = 2.54 centimeters exactly, or 1 foot = 0.3048 meters exactly. The other was the older US survey foot, which was defined as 39.37 inches = 1 meter exactly, or 1 foot = approximately 0.304800609601 meters, or multiplying US survey feet by the fraction 1200/3937 to get meters.

The US survey foot has been around since 1893 while the international foot was established in 1959 and is slightly more exact. One of the reasons we retained the US survey foot was because of our state plane coordinate systems, which were derived from the national geodetic control network, and are based on the relationship of 1 meter equaling 39.37 inches exactly. Fundamental survey units, such as rods, chains, statute miles, acres, sections, and townships, all depend on the relationship of 1 meter equaling 39.37 inches exactly.

Using two measurements for the same unit have been confusing over the years. But now the US survey foot will be obsolete by January 1, 2023. Click below to read more about it!