I have a large amont of CAD data in several local Mine Grid projections. These Mine Grids can be translated to UTM by rotating around the X,Y and Z axes, applying a false northing and easting and elevation correction, and scaling (not necessarily in that order, and I'm still trying to figure out the order of operations).

Mine Grid to UTM conversion - 7 parameters:

[INDENT]x-translation

y-translation

z-translation

x-rotation

y-rotation

z-rotation

scale factor[/INDENT]

I looked at the Local Cartesian Projection in ArcGIS, but it is defined relative to a geographic point (Lat/Long) rather than a Projected point (Easting/Northing) and the parameters for this projection are not well defined in terms of how they should be specified. I had thought that my grid should be based around the x/y/z translation in my 7 parameters, but then what would my false easting and northing be? And can I specify an azimuth that is rotated around all three axes somehow? Or is it that the software can determine the x and y axes rotation automatically when it places the plane tangent to the specified point and all I'm putting in as an Azimuth is the z axis rotation.

Local Cartesian Projection - 6 Parameters:

[INDENT]False Easting

False Northing

Longitude of Center

Latitude of Center

Scale factor

Azimuth [/INDENT]

Does this make sense to anyone?

Mine Grid to UTM conversion - 7 parameters:

[INDENT]x-translation

y-translation

z-translation

x-rotation

y-rotation

z-rotation

scale factor[/INDENT]

I looked at the Local Cartesian Projection in ArcGIS, but it is defined relative to a geographic point (Lat/Long) rather than a Projected point (Easting/Northing) and the parameters for this projection are not well defined in terms of how they should be specified. I had thought that my grid should be based around the x/y/z translation in my 7 parameters, but then what would my false easting and northing be? And can I specify an azimuth that is rotated around all three axes somehow? Or is it that the software can determine the x and y axes rotation automatically when it places the plane tangent to the specified point and all I'm putting in as an Azimuth is the z axis rotation.

Local Cartesian Projection - 6 Parameters:

[INDENT]False Easting

False Northing

Longitude of Center

Latitude of Center

Scale factor

Azimuth [/INDENT]

Does this make sense to anyone?

Yes, but I don't think we can emulate it easily. Generally, we're still working in 2D, particularly with the map projections. I haven't really seen a 3D conformal transformation for a local grid before.

There's no way to really easily build a custom prj file, but it's often possible. As you've seen, we have a map projection method called 'Local' which supports a center point, azimuth, scale factor, and false easting/northing. The azimuth value allows us to incorporate a plane rotation. Another projection that can support similar parameters is RSO (rectified skew orthomorphic). Because these work at the spheroid/ellipsoid level, the parameters you have to convert to/from UTM won't be directly applicable. If you have any information on the local grid's center/origin point, that can be used.

The steps are:

1. Create two sets of corresponding point shapefiles: one in local grid, the other in UTM.

2. Make sure the UTM data has its coordinate system defined. Do not define a coordinate system on the grid data.

3. Add both to ArcMap.

4. Open data frame properties and select the coordinate system tab.

5. Create a new, custom projected coordinate system (pcs).

a. Name: anything you want

b. Geographic coordinate system: same as the UTM zone, likely NAD 1983

c. Projection: Local

d. Parameters:

i. Longitude of center/latitude of center: enter if known, if not, try to identify a point near the center of the data or near nice even grid coordinates

ii. Scale factor: leave = 1 for now

iii. Azimuth: Try entering the value you have but it's almost certainly incorrect (that's because angle is based upon the UTM zone which already has an angle from north)

iv. False easting/northing: if you know the center coordinate, use those values

e. Units: whatever the grid is in

6. OK all dialogs. You will see the UTM data being projected on-the-fly to the new custom pcs. The 'unknown' data is just displayed because ArcMap can't reproject it.

7. You can now modify/edit the data frame's coordinate system. Change the azimuth, scale factor, etc. You want to line up the state plane data with the grid data.

You then work back and forth, with change the azimuth/scale (possible origin), then updating the false easting/northing values.

Melita

Edit on 7 May 2015: Replaced bad characters (from smart quotes?).