topic Re: Projection Recommendation for local data in Map Projections Questions

Projection Recommendation for local data

GregYetman — Thu, 17 Jul 2014 19:13:21 GMT

I need a custom coordinate system for some large scale data (1:500) that I am using to make a basemap. The data are in MTM Zone 1, a Canadian UTM variant. The new coordinate system needs to be rotated by 45 degrees. Unfortunately, I cannot use the data frame rotation in ArcMap as I need to create a tile package to use as a basemap in ArcGIS Server that will be exposed through ArcGIS Online, which currently does not support layers rotated in the data frame.

I was thinking of using Hotine (Oblique Cylindrical Orthomorphic), would anyone recommend something else? It should be something that is supported for on-the-fly projections in ArcMap so that the people who maintain the data can use it with other layers. It should also have characteristics similar to UTM; that is, distortion minimized near the central meridian/point of the projection.

Any other suggestions for a work-around to get the data in ArcGIS Online as a basemap would be appreciated!

Re: Projection Recommendation for local data

DanPatterson_Retired — Thu, 17 Jul 2014 19:19:12 GMT

Why does the coordinate system need to be rotated? Is it for visual effect or analytical? MTM is pretty darn good projection (SF 0.9999) and, as you know, used by many municipalities/provinces for mapping purposes

Or keep your data in MTM and set the dataframe properties to something else that approximates what you need

Re: Projection Recommendation for local data

GregYetman — Thu, 17 Jul 2014 20:06:44 GMT

It's for visual purposes only; just viewing, queries and printing. End users are used to the rotated view where the buildings align with the page. Data editing and collection will still be done in MTM 1 (by CAD operators and surveyors). I would really like to have everything in the Geodatabase stored in MTM and just rotate the frame but unfortunately it's not supported by Server and Online yet.

Re: Projection Recommendation for local data

DanPatterson_Retired — Thu, 17 Jul 2014 20:17:41 GMT

You are going to cause yourself a whole lot of problems reprojecting the data just so someone feels comfortable viewing it in a certain way...tongue-in solutions...tilt their heads, tilt the monitor

Re: Projection Recommendation for local data

MelitaKennedy — Fri, 18 Jul 2014 18:12:47 GMT

If you want to actually change the direction of north, you may need to use RSO (rectified skew orthomorphic) or the "Local" projection. The latter is Orthographic, but on an ellipsoid. RSO has two rotation parameters. Azimuth is the analytical one. The other one re-orients the map to North. Its value is usually the same or very close to the azimuth value. In your case, you want to leave it set to zero or some other value relative to the azimuth value.

Melita

Re: Projection Recommendation for local data

GregYetman — Mon, 21 Jul 2014 11:49:05 GMT

Thanks, that did the trick!