Creating a Ground Coordinate System


Have you ever wanted to add GIS data that is in GRID to your Civil project that is in Ground through FDO? Here is a two step procedure for creating a Ground Coordinate System. When creating a ground coordinate system for State Plane Zones that use the Lambert Conformal Conic projection there is no place to enter the scale factor. To get around this you must create a custom Ellipsoid.

Sample Scale Factor: 1.000130

First Step: Create a new Ellipsoid Definition

1. In the Map Setup Tab, from the Create dropdown select Create Ellipsoid Definition.

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2. In the Create Ellipsoid window select Create a new ellipsoid from and existing one.


3. Select GRS1980 from the list. In the Create Ellipsoid window hit Next.

4. In the Modify ellipsoid window, Modify Code: by appending the County Name (or project name).

5. Copy and paste the value from the Inverse flattening to Notepad.

6. Copy the Equatorial radius (meter) to Windows calculator and take it times your combined scale factor (1.000130)

7. Paste the result back to the Equatorial radius (meter). Notice the Inverse flattening changed.

8. Now copy the original value for the Inverse flattening from notepad and overwrite the change.

9. It should look like the image below. Pick Finish.


Second Step: Create a new Coordinate System Definition

1. In the Map Setup Tab, from the Create Coordinate System Definition


2. For the Specify starting point select Start with a coordinate system and hit Next

3. In the Specify coordinate system window select the radio button for Create a new coordinate system from an existing coordinate system and pick the Select button.


4. Select TX83-SCF by typing in the search bar and pick the Select button.

5. Select Next.

6. Give the Code: a modified Name (TX83-SCF_Chambers_GR). Modify the Description if you like.

7. In the Modify coordinate system window pick the radio button for Non-geodetic and pick the Select button to choose the new Ellipsoid you created by picking on the Status dropdown and selecting User Defined. This is your new Ellipsoid with the scale factor applied. Select Next.


8. Multiply the False eastings and False northings by the scale factor and replace them in the window and select next.


9. Do not change anything in the following window and select Next

10. Select Finish on the last page to complete the new ground coordinate system.

Now you will be able to add GIS data to a Civil project by setting your project to the newly created coordinate system


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