We had a couple of drawings started (shape files imported as well as field survey data) in international foot instead of the US survey foot. Is there a way to correct this error without re-importing the shape files and field survey data?
If everything in the drawing is in consistent units than all you have to do change the drawings units. There is no error that you would need to correct. For example, if I draw a line 12 'units' long and my drawing is set to 'inches' then the line 12 inches. Change the units to 'miles' and the line is 12 miles.
If however you imported a shapefile and Autocad did a special conversion you that was incorrect you are best off reinserting.
Based on your post and because you are importing shapefiles I would make sure that you have correctly specified your drawing coordinate system (i.e.. Washington State Plane North, NAD83 HARN, US Survey feet) and are not inveterately doing a conversion during import.
Also, if the survey data was brought in using the survey database, you need to ensure that the survey database is using the proper units as well. For example, drawing in International Feet, but Survey Database in US Survey Foot. C3D will convert your data.
As long as your coordinate zone is correct, and your drawing units = survey databse units, you should be fine, and C3D will not convert the data.
This is even true if say, your survey file, let's say a .CSV file, was measured in US Survey Foot, but your survey database and drawing are set to International Foot. That's actually fine, as C3D wont convert the data, because it "thinks" it (the .CSV file) is already in IF, not something else.
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