by JoePaiva » Thu Nov 26, 2009 4:02 am
It would be nice to support U.S. Survey feet. many "civilians" consider it useless, but to surveyors, cartographers and others, it is a significant difference, amounting to about two parts per million. Its origin is in the latter half of the 20th century, when the international foot was defined as International foot = [m] / 0.3048 or 25.4 mm to the inch. Due to accurate mapping of the United States in foot units by the U.S. National Geodetic Survey (google National Geodetic Survey to find their website which includes a U.S. survey foot vs. international foot discussion) historical documents now had different meaning for positions in the U.S. that were accurately determined. Thus the U.S. survey foot, using the old definition of U.S. Survey foot = [m] x 3937/1200 was born. It would be a service to many professions to support this conversion. You should know that software used by cartographers, surveyors, GIS professionals frequently support U.S. survey feet. But there is much software that doesn't resulting in appreciable errors in calculations when long distances are converted (a little over 12 inches in 100 miles).