Lining up CAD data - georeferencing

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12-29-2015 08:30 AM
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Regular Contributor III

I received a .dwg file of a county drain from an engineering firm that doesn't display in the correct location (it's very far to the west). In the past, I've georeferenced these types of files and converted them to shapefiles. I can convert them to shapefiles, but they still display in the wrong location.

When I try to georeference the CAD polyline, ArcMap crashes and closes every time with the 'a serious application error' message when I try to add links. Fit to display works ok.

I can't get much information from the engineering firm. They did try converting it to a shapefile on their end, but somethings is wrong with the result. None of the files will open.

Based on measuring corresponding features in both the reference data and the CAD file, my guess is that the CAD units are inches, while the GIS data is in State Plane international feet.

Running ArcMap Advanced 10.3.1 over a VDI connection, Windows 7, 64 bit. Any ideas on how to fix this? Thanks.

Update - I did get it to line up by a trial and error process of customizing a projection file, but would still like to solve the georeferencing issue.

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New Contributor II

Check out this patch.

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Regular Contributor III

Thanks Kyle, Looks helpful. I'll ask IT to install this (no local copy of Arc, running of a server).

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Esri Notable Contributor

Showing up far to the west could mean an incorrectly identified coordinate system. For instance, the coordinates are in lat/lon but the definition is for UTM or State Plane. The "small" lat/lon coordinates would then show up southwest of true projected coordinates.

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Regular Contributor III

Thanks Melita. The CAD data displays ~ 2500 miles west, slightly south (don't recall by how much -visibly so, but not nearly as far).

Creating a world file ran into the same crash problem referenced in the patch Kyle referred to.

I ended up modifying the projection file used by the reference data (State Plane) using the method described in Margaret Maher's book 'Lining Up Data in ArcGIS' for non-rotated local coordinates.

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MVP Honored Contributor
Update - I did get it to line up by a trial and error process of customizing a projection file, but would still like to solve the georeferencing issue.

I can't help with your georeferencing issue, or the fact the engineering firm was no help, but it does sound like they are using a custom coordinate system. There must be someone at the firm who knows how to translate the coordinates into a standard CRS. Whether or not the CAD operator knows it, the software is obviously using a CRS.

I've run into this relatively often with custom local UTM zones from CAD, which have either a false easting or northing, and with some prodding the engineers should be able to tell you. The secret term that seems to twig the engineers' memory is "ground coordinates" (which they use) vs. "grid coordinates" (which are the standard UTM coordinates).