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I have CAD data that I need to incorporate into a GIS analysis. The CAD data does not have a defined projection, but the drawings include a table of survey baseline points. I need to know if I can build a custom projection based on this table:

Survey baseline coordinates

Is this enough information to construct a custom projection string, or do I need more data?

The documentation references a "Borough of Queens Coordinate System", which turns up nothing in Google. My hope was that it's some obscure projection only used in New York City but that it could be recreated using the above table.

  • More likely you need to identify the coordinate system/projection rather than create a custom one. Where in the world is this? It's also possible that it's using a custom coordinate system, in which case if you don't have access to the definition of that system or any known control points your only option is going to be a rough georeferencing. – Chris W Jun 10 '14 at 18:31
  • The documentation references a "Borough of Queens Coordinate System", which turns up nothing in Google. My hope was that it's some obscure projection only used in New York City but that it could be recreated using the above table. – spencerrecneps Jun 10 '14 at 18:40
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    More likely it either is New York State Plane Long Island 3104 or a derivation thereof. The problem is the possible derivation thereof part - if they've modified the state plane system to give desired numbers for that particular Borough, and you don't know how the transformation was accomplished or what base points it used, you won't be able to create a custom projection out of it. The suggestion would be to try assigning it that state plane projection and see where it comes in relative to some known data. – Chris W Jun 10 '14 at 18:59
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There is some information in a Point of Beginning online article titled The Xs and Ys of the Big Apple. The Queens Borough or Queens Topographic system has an origin near Amsterdam and 225th St. That puts Queens into the southeast quadrant, thus positive southings and eastings.

It's a local planar system, so not directly related to any of the projections used by the State Plane system. VAlues are in feet--I'm guessing US survey feet.

If the software you want to use doesn't support positive axis directions other than easting,northing, you may have to make the southings negative to convert them to a positive north axis.

This reference was just the first one returned by Google and searching 'Queens borough coordinate system' (no quotes). There may be other information available.

  • Thanks. I had found that article but couldn't really make heads or tails of it. It's all a bit technical for me. – spencerrecneps Jun 10 '14 at 19:48
  • Ha! That's the same article I linked to in my comment. Good to see I can find what I'm looking for even when I don't know what it is. :) Guess I should have read the whole thing through. – Chris W Jun 10 '14 at 20:47
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This does exist but it is Vertical a datum.

http://law.justia.com/codes/new-york/2006/new-york-city-administrative-code-new/adc027-158_27-158.html.

So as Chris states you need to find what the horizontal system is. We can rule out UTM, lat long, Military grid base on these numbers. Strangely enough ~-73 is queens in longitude but I suspect that is coincidence.

  • I suspected that might be the case based on what I saw here, but I wasn't sure. And if you really want some entertaining reading, you can try this article. – Chris W Jun 10 '14 at 19:09
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There is not enough information to say exactly what it is. Since it is survey data, it will be

  • either a local, arbitrary, ground-based system (but probably not since coordinates in such systems tend to have much smaller values for convenience)
  • or a conformal projection, such as the relevant State Plane system for Queens.

If you cannot determine the CAD coordinates system and if you have some points known in both the CAD and the GIS, you can calculate the transformation between the two systems.

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