Example files with local coordinates, WGS84 positions, and a geoid model field file are available for download in a zip file below. With these files you can use the simulator Determine Coordinate System program to practice this routine. My thanks to Henri Ayers for providing these files and the insight into the process.

Right-click here and select Save Target (or Link) As...

This process only works with a geoid model that is referenced to the WGS84 ellipsoid and has been created with the Apply on the local side option selected.

If you do not have such a model, you need to create this geoid model using the WGS84 ellipsoid in Leica Geo Office (LGO) and check the "Apply on the local side" box as shown below: The name of your model should describe its usage.

Next create a geoid model field file in LGO using this geoid model

and transfer it to the receiver System RAM.

Create a job on the receiver which contains the local point's known local coordinate.

In the example files, our known point is NBS1:

Occupy the known local point with your RTK rover.

Our NBS1 example was observed as:

From the Main menu, select Programs and then select Determine Coordinate System from the Programs menu:

Press F1[CONT]

Give your coordinate system a name, select the appropriate files, and select One Pt Localistn as the method:

Press F1[CONT]

The Transformation Name will be the same as the coordinate system. Make sure the Transormation type is Onestep, and the Height Mode is Ellipsoidal as shown:

Press F1[CONT]

Select the geoid model field file you created above (the example provides the model shown):

Press F1[CONT]

Select the point to match in Pos & Height. In the example, select NBS1:

Press F1[CONT]

Next determine your rotation. Normally we will just use WGS84 North as shown:

Press F1[CONT]

Select how you want to compute the ground scale. Normally we will just use the ellipsoidal height of the measured known point as shown:

Press F1[CONT]

View your results:

Press F1[STORE] to save the coordinate system. You will be returned to the main menu. If you select Survey, you see that the WGS84 job is the active job, and the coordinate system you just created is the active coordinate system.

You are now done and can survey and view your data in local ground coordinates with elevations relative to the known point, and with the geoid model taken into account.

Using the example file, we can view the position of ORM1 and see that its ortho height is 115.499.

If we had done a standard one point localization by selecting orthometric as our height mode, and not using a geoid model, the height of ORM1 would be 115.505.