Product(s): | OpenRoads Designer |

Version(s): | 10.10+ |

Area: | General |

A Helmert Transformation can be applied to the Geographic Coordinate System to account for the ground to grid factor between coordinates.

To apply a Helmert Transformation, please follow the steps outlined below:

1. Open the Geographic Coordinate System Dialog. (OpenRoads Modeling -> Utilities -> Geographic -> Coordinate System)

2. Select Properties in the upper left hand corner of the dialog.

3. In the Geographic Coordinate System Properties, navigate to Coordinate System Modifiers.

Select the dropdown for Local Transform Type and choose Helmert Transform

4. When using an Average Ground to Grid factor in a Helmert Transformation:

Helmert A = Combined Ground to Grid factor

Helmert B = 0

Offset X = 0

Offset Y = 0

Offset Z = 0

If provided with a Grid to Ground factor, you will need to inverse this value to receive the Ground to Grid factor.

Additional Information on Helmert Transformations is available in the pdf below:

Understanding Mapping Reference Frames for Engineering Projects.pdf