Seems having two different feet plus meters can cause all sorts of problems in surveying. The comments below are from the web site below. Read paragraph three for what has been happening.
Michael Payne http://www.axiomint.com/microstation_tips/survey_vs_international_foot.htm As to the comments about the average surveyor not encountering distances large enough to be a factor, please use appropriate caution when using State plane coordinate systems! USGS monument coordinates given in meters need to be converted to the "old survey foot" with the proper conversion factor (12"/39.37"), and on a computer calculator to as many decimal places as possible. Also, take great care in mixing the MicroStation conversion (by referencing by coincident world a metric drawing, for example) because it uses the international factor. The only reliable way to reference a metric drawing is to make sure it also lines-ups/snaps-to a similar point or alignment converted and displayed (in both the foot drawing and the metric drawing) by InRoads, because InRoads geometry transformation (feet-meters or meters-feet) employs the "old survey foot" factor. Bentley does have a work-around for changing the settings in a MicroStation drawing, but it has to have been created by the surveyors or mapping company that way in the first place. Also, especially with the new 1983 datum, it is now even more important to "check in" at monuments after several miles, because the difference between the State plane coordinates and distances measured along the surface is more. The State plane coordinates now occur at elevations below 0 (zero) for most of the US. Many agencies employ "project grid factors" that more closely relate surface measurements to the coordinate system, but that's a whole other discussion. We have seen entire photogrammetric areas done wrong after everybody went back to feet from meters. USGS monument info was being given out only in meters for a while. It started with just the one error, using the wrong conversion for the starting coordinate. From there they coordinated the photo target points, and then generated miles of mapping. Rather than running to the State, we met with them (the consulting company), and showed them what we suspected happened. They agreed, fessed-up to the State themselves, and had to redo it on their own dime. Michael Payne 1 Thorton Court Potomac Falls VA 20165 USA
