Short Version:
Is there an easy way to take the Coordinate System Details output from TGO or TBC to define a custom coordinate system?
Long Version:
We have set up a control network to do some survey work in Wyoming. Previously, while doing work in Utah and Colorado, we have used information generated in TGO to create a custom coordinate system that enables us to communicate with CAD and the surveyors. While duplicating this process for our work in Wyoming, I noticed that when calculating latitude and longitude from a local x,y value I am not seeing the expected value. This is not the case for our work in Colorado and Utah. As far as I can see, the only difference between the projects is that the State Plane zones for Utah and Colorado use Lambert Conformal Conic whereas Wyoming uses a modified UTM.
This was done by taking the origin of the State Plane zone in question and using the scale factor given by TGO along with the origin of our surveyors local coordinate system to come up with a new False Northing and Easting. The new False Northing and Easting along with the Scale Factor are then used to modify the State Plane Zone to create a custom coordinate system. This has given very satisfactory results.
Here's the math we're using:
New False Northing: Fn
State Plane Zone Origin Northing: SPn
Scale Factor (from TGO): SF
Local (ground) Northing of our local coordinate system): Ln
Northing offset (to differentiate local coordinates from State Plane Coordinates): On
State Plane Northing of our local origin: Gn
Fn = (SPn*SF)-((Gn*SF)-Ln)
Ln = Gn-On
The calculations for the False Easting are similar, simply replacing northing values with corresponding easting values.
On the CAD side, they input the local northing and easting, the corresponding State Plane northing and easting, and the inverse of the scale factor from TGO. This process worked fine for our Wyoming data.
Is there anything different about the calculations needed to come up with the modified False Northing and False Easting given that we are trying to shift a UTM grid rather than a Lambert Grid?
