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Relationship between CAD data and Projection

Question asked by dj1991 on Nov 7, 2013
Latest reply on Nov 15, 2013 by dj1991
Hi, I have a loose understanding of projections, and I am trying to figure out from a CAD perspective how projections are defined.

For example, when someone sends me CAD data it has no projection defined, I convert it from a DWG to a shapefile, and then since I know roughly where it is I just try to define the projection with a few guesses ie. UTM zone 11 in meters, and it works out.

What I want to find out is how the projection is defined when the data is first drawn in CAD (I have never used CAD and don't know anything about it really). Ie. When an engineer sits down to draw something, how do they determine that it is in UTM zone zone 20 and not MTM zone 6 or something.

The reason I need to know is that I can't figure out the projection of a certain DWG and I am trying to relate to an engineer what information they can give me to help me define the projection

Thanks.

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