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<TITLE>Surveyors, AARRGGHH!!!</TITLE>
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<P><FONT FACE="Tahoma">I just received an AutoCAD file of a survey produced in the late 1980's. Additional field work was done in 2004 and this revised survey is the CAD file I have.</FONT></P>
<P><FONT FACE="Tahoma">I assumed the survey work was done in State Plane Coordinates NAD83, but when I created a projection file for this survey it ended up about 30 miles west of the site when I let the file project on the fly!</FONT></P>
<P><FONT FACE="Tahoma">So I went back and created a new projection file, this time establishing the coordinates as State Plane Coordinates (SPC) NAD27. When I imported the CAD drawing I immediately saw that the CAD drawing was coming out southwest of where it should be by about 50 ft. I realized that the surveyor apparently had taken a SPC NAD27 file and offset it by the correction factor from NAD27 to NAD83 without taking into account the difference in the offset that also exists between the two projections (I have been told that this 30 mile offset was added to the SPCs to make if obvious when the wrong projection was being used).</FONT></P>
<P><FONT FACE="Tahoma">The problem is that, if I reproject the SPC NAD27 file to SPC NAD83, it adds the offset between the two datums back in again!!! Short of getting the surveyor to correct their file (not likely since the job was finished in 2004) how do I get this error corrected???</FONT></P>
<P><FONT FACE="Tahoma">By the way, I tried telling the PRJ file that the coordinates were SPC NAD27 and the datum was NAD83, but that didn't work. Also, I found that the reprojection tool in the toolbox doesn't work for CAD files.</FONT></P>
<P><FONT FACE="Tahoma">Of course, ultimately I'm trying to get this whole thing into FDEP Albers for my map.</FONT>
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<P><B><FONT SIZE=6 FACE="Brush Script MT">-- John</FONT></B>
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