I have a friend who travels around the country servicing natural gas pipelines. As part of his duties he has to translate latitude / longitude coordinates into state, township, range, and section information. He was doing this by hand dozens of time per day. I found an API from the Department of the Interior’s Bureau of Land Management which accepts coordinates and responds with the exact information my friend needed.
I created a PHP client that can consume the API and another class that uses PHPExcel to parse an XLS spreadsheet with coordinates and populate it with the additional information.