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I have a problem that I am hoping might have multiple solutions. I am working with research data that was collected on an arbitrary grid, with units in m, datum point of 1000E, 1000N. The grid is rotated 34.5 degrees from geographic north. I've created a map project with our data on it, with a custom coordinate system. I would like to use ArcGIS basemaps for background, and accurately load GPS data (UTM NAD 83) on the same map.

I have one dataset from our surveyors that gives me a set of matching data points in both our custom coordinate system and UTM NAD 83. So far I have been able to line up my maps by

  1. Loading the site data I want on my first data frame (A) in the custom grid.
  2. Rotating data frame A by 34.5 degrees
  3. Adding the surveyor points to data frame A based on the site grid coordinates
  4. adding a new data frame (B) in NAD 83 and loading basemaps and the surveyor points based on UTM coordinates
  5. setting both frames to the same zoom (since both have units in meters)
  6. panning until my data points line up on both maps.This works and our site data successfully lines up with geographic basemaps and GPS data.

How do I link these two layers so that I can pan and zoom in one and have the other mirror/follow it?

I tried the solution given here: Link Dataframes in ArcGIS, using data frame A as the primary/other frame, and it didn't work: it rotates data frame B to 34.5 degrees, mis-aligning my maps, and when I pan data frame A, B still won't move. Since my coordinate systems are different, and since I have a very specific alignment point, this solution does not seem applicable.

Is there a way to create a transformation for my custom grid to project it into a normal UTM NAD 83 data frame, and avoid this problem entirely? Or to somehow geo-reference one data frame to another? I want to be able to zoom and pan without re-aligning my maps every time, and to be able to use the maps in places where there are no survey points present for alignment.

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Younie
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    Do you have the lat/lon coordinates for the center of the local grid? If so, try defining a custom "Local" projected coordinate system. It supposed an azimuth value (the rotation), scale factor, and false easting/northing (1000,1000). Use that for the data frame's coordinate system and see if the basemap and gps line up with the arbitrary grid data. – mkennedy Jan 05 '16 at 18:31
  • This partly worked, thank you! My new projection did work as far as aligning frames to the same rotation. However, I am not sure how to use this projection - do you mean there is a way I can have everything in the same data frame? I applied it to data frame B and it worked, except that again when I tried to use the Linked Layers solution (above), data frame B doesn't pan or zoom with frame A. All the panning and zooming options on B go grey, and it rotates with A when I set a new rotation, but it is still not moving together with A for pan/zoom. – Younie Jan 05 '16 at 20:09

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If you have the lat/lon coordinates for the center of the local grid, try defining a custom "Local" projected coordinate system.

The "Local" projection algorithm supports an azimuth value (the rotation), scale factor, and false easting/northing (1000,1000) plus the center of the projection.

A quick way to check whether the definition will work is to define it as the data frame's coordinate system and see if the basemap and GPS layers line up with the arbitrary grid data. At this point, the arbitrary grid data should have no coordinate system. (All data is in the same data frame)

Using this method, you can also tweak the data frame's coordinate system if the layers don't fit together properly. Sometimes the person who defined the data leaves out information like a grid-to-ground correction (often a scale factor).

Once the "known" data is overlaying the "unknown" (arbitrary grid) properly, save the data frame's coordinate system as a "Favorite." Switch over to the Catalog window and define the unknown data's coordinate reference system with the Favorite you just saved. Refresh the data frame and you're good to go.

mkennedy
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  • Thank you! This is exactly what I needed, especially the explanation of what to do with my arbitrary grid data to make it all line up. I did notice that instead for a center projection point, I had to use the lat/long of my datum itself to make the different layers line up correctly. – Younie Jan 05 '16 at 21:19