topic Re: Create a projection file in Coordinate Reference Systems Questions

Create a projection file

DavidSantos — Tue, 07 May 2019 14:18:17 GMT

I would like to create a .prj file in order to exchange data between CAD and GIS.

For references, I have 9 ground control points in both the local grid and SPCS NAD83 equivalent and a table with the following values from the surveyor.

Projection Type: Lambert Conformal Conic 2 Parallel
False Northing: 1000000 usft
False Easting: 3000000 usft

Horizontal Adjustment Type: Plane
Origin Northing: 1347119.328 usft
Origin Easting: 2338925.736 usft
Translation North -1000000.629 usft
Translation East: -999854.751 usft
Rotation: -0°00'21.046132
Scale Factor: 1.000323

Reading some of the articles, I am going through a bit of information overload. I am looking for a method to develop the .prj for this scenario in particular.

Thank you,

David

Re: Create a projection file

Anonymous User — Tue, 07 May 2019 14:55:18 GMT

Hi David,

We might need some additional information from the surveyor to create a .prj file from these specifications, as I'm not sure how the information provided by your surveyor will fit into the Esri format; it looks like we are missing a latitude of origin, central meridian, and a few other things, but maybe others here will have a better idea of how to format this. I can at least let you know how to start the process of creating a .prj file in general, though!

To create a .prj in ArcMap: (here's a video of this too 05.07.2019-07.49.36)

Open a new blank map
Right-click on the Layers data frame in the Table of Contents and select Properties
If necessary, click the Coordinate System tab
Click on the Globe icon at the top of the tab and select New > Projected Coordinate System
Enter all of the pertinent parameters into the form
Once you've entered all of the projection information, click OK. You'll see the new coordinate system under the "Custom" folder in the Coordinate Systems tab
To export as a .prj, right-click on the new coordinate system and select "Save As." This will create a .prj file.

The process is the same in ArcGIS Pro, though it looks a little different. Here's a video of that workflow:

05.07.2019-07.53.05

Hopefully that helps!

Best,

Lauren

Re: Create a projection file

DavidSantos — Tue, 07 May 2019 15:25:06 GMT

Sorry, I was more concern on the values for the horizontal shift that I omitted a lot of useful information.

Projection Projection Type: Lambert Conformal Conic 2 Parallel
False Northing: 1000000 sft
False Easting: 3000000 sft
Origin Latitude: 39°20'00.00000 N
Origin Longitude 105°30'00.00000 W
Parallel 1: 40°47'00.0000N
Parallel 2: 39°43'00.0000
Semi major Axis: 20925604.474 sft
Flattening: 298.2572
Project Elevation: 7500 ft

And the typical values in the local grid look something like this:

Y=364,046.135 X=1,359,194.067 Z=6348.177

How/where do I apply the shift values when creating the prj?

Thank you for the video links.

Re: Create a projection file

MelitaKennedy — Tue, 07 May 2019 18:12:27 GMT

Hi David,

The base coordinate reference system is NAD83 State Plane Colorado North (US survey feet). The flattening you listed is rounded compared to what's normally used, so I would just use the standard NAD83 definition.

You've got scale, rotation, translation values so you could try georeferencing the CAD data this way:

Defining a coordinate transformation

It also talks about setting up a world file instead. With either method, you would assign (use a prj file) that has the NAD83 State Plane Colorado North (US survey feet) definition.

It's sometimes also possible to directly design a coordinate system that incorporates the translations, scale, and rotation values. Your case would be difficult because of the rotation. Lambert conformal conic doesn't have that parameter so you would have to try adjusting the central meridian value instead. It would be tedious, so I would try the other solutions first.

If you want, please send me an email (mkennedy at esri dot com) and I can send you two documents that discuss this.

Melita

Re: Create a projection file

ZachEdwards_WDSGIS — Fri, 02 May 2025 19:37:04 GMT

I know that I am chiming in here super late but i would take you up on the two documents that you mentioned above Melita! If easier, you can email me at gis@allterracentral.com.