Thursday, July 06, 2006

Left Foot Left Foot, Which One's Right? US Foot vs International Foot

Today Melanie asked what the LandXML import did when it converted from US Survey Feet to International Survey Feet. I have seen that a million times myself and never looked up the difference.

So today, I did! I found the definitive answer from the:

"Any data expressed in feet derived from and published as a result of geodetic surveys within the United States will continue to bear the following
relationship as defined in 1893:

1 foot = 1200/3937 meter

The foot unit defined by this equation shall be referred to as the U.S. Survey Foot and it shall continue to be used, for the purpose given herein, until such
time as it becomes desirable and expedient to readjust the basic geodetic survey networks in the United States, after which the ratio of a yard, equal to 0.914 4 meter, shall apply."
So, a US Foot = 0.30480060960121920243840487680975
and an International Foot = 0.3048