Projection

A projection is used to transform local geodetic coordinates into local grid coordinates. GNSS coordinates are relative to the WGS‑84 ellipsoid. To work in local grid coordinates during a GNSS survey, you must specify a projection and datum transformation. You can reduce any discrepancies between the WGS‑84 coordinates and the local grid coordinates by performing a site calibration.

Enter an appropriate default project height value for the software to correctly calculate a sea level correction and then apply it to the grid coordinate.

Initial projection coordinates are projections that are computed using specified projection routines. Some countries use shift grids to apply corrections to these coordinates. The corrections are generally used to fit the initial coordinates to local distortions in the survey framework, and so cannot be modeled by a simple transformation. You can apply a shift grid to any type of projection definition. Coordinate systems that use shift grids include the Netherlands RD zone, and the United Kingdom OS National Grid zones. The OS National Grid zones are treated as a standard Transverse Mercator projection plus shift grid.

Shift grid files are installed to the desktop computer running the Coordinate System Manager utility, which is installed with Trimble Business Center.

To apply a shift grid to a projection definition in Trimble Sync Manager, in the Projection tab of the Coordinate system definition dialog add the grid file in the Shift grid field.

Use a projection grid to handle projection types that are not directly supported by the software coordinate system routines. A projection grid file stores local latitude and longitude values that correspond to regular northing/easting positions. Depending on the direction of the conversion, either projection or local latitude/longitude positions are interpolated from the grid data for points within the grid extents.

Use the Coordinate System Manager utility provided with Trimble Business Center to generate the defined projection grid (*.pjg) file. For more information, refer to the Coordinate System Manager Help. Transfer the projection grid file to the controller.

To use the projection grid in Trimble Sync Manager, in the Projection tab of the Coordinate system definition dialog, select Projection grid in the Type field and then add the grid file in the Projection grid field.

SnakeGrid is a coordinate system with minimal scale factor and height distortion, even when projects extend for many hundreds of kilometers.

A job using a SnakeGrid coordinate system must use a custom SnakeGrid parameter file. These files are obtained through a licensing arrangement from the UCL Department of Civil, Environmental and Geomatic Engineering. Each SnakeGrid parameter file is customized for a specific project alignment envelope. Go to SnakeGrid.org for details.

To choose a SnakeGrid projection in Trimble Sync Manager, in the Projection tab of the Coordinate system definition dialog, select SnakeGrid in the Type field and then add the grid file in the SnakeGrid field.