GeoCalc Projection

The GeoCalc Projection Mode allows Global Mapper users administrative control of geodetic parameters through Geographic Calculator*. Once enabled, Global Mapper will access the Geographic Calculator datasource (GeoCalc Library) for data re projection and coordinate transformations.

Additional support is enabled for:

  • Vertical datum transformation support for an expanded library of local geoids, ellipsoids, and local offset models
  • Vertical datum support for Tidal vertical references in North America
  • Custom coordinate system support and easy sharing of custom parameters between multiple users
  • The Administrative control of geodetic parameters allows administrators to limit Global Mapper access to the GeoCalc Coordinate Transformation Library through Geographic Calculator, so that users only see and use what you decide via Geographic Calculator.
    For Example if users only work with data in Canada, you can shut off all non-Canadian systems in Geographic Calculator and these would then be unavailable in GeoCalc Projection.

If you have registered Global Mapper and the Geographic Calculator applications, the GeoCalc Projection mode may be enabled by clicking the Enable GeoCalc Projection Mode button in the Global Mapper toolbar.

Auto-select most accurate Transform

In Geographic Calculator, Datum Transformations have an Accuracy field. Datum Transformations from EPSG have been updated to include the accuracy values specified in the EPSG dataset, the user may also set these to set a known, numerical, accuracy value through the Datasource menu in Geographic Calculator.                       

Performing a Projection change or a Transformation using GeoCalc Projection

To perform a Projection change or Coordinate Transformation using the Geographic Calculator datasource go to Tools > Configuration and select the GeoCalc Projection tab.

This tab will display the current Coordinate System, Datum, Units, Vertical Reference and Vertical Units. Changing these values will initiate a Projection change, or a Coordinate Transformation.

To save any changes made to the data's Projection, or to perform a Coordinate System/Datum Transformation, hit the Apply button after configuring the Coordinate System, Datum, Units, and Vertical Reference.

Load From File... this may be used to load a coordinate system contained with in a Projection (.prj), .txt or Esri aux.xml file format. Use Save Projection To File... to save a projection or system to a Projection (.prj) file.

The option to Reload Datasource may be used if a new system has been added directly to the Geographic Calculator's datasource, the relad option will 'refresh' the list of available systems to include the recently added system.

Coord Transforms: - When a coordinate transformation is performed, the transformation from Geographic Calculator will populate in this window. Double-clicking on the transformation line will bring the details of the transformation up in the Geographic Calculator datasource window.

For more information on any of the Coordinate Systems, Units or Datums available hit the blue 'I' button next to that field. This will bring up a description from the Geographic Calculator datasource (See below).

The information window for a Coordinate System, will display the EPSG code (if available) the Identification tab and specific information about the Coordinate System's geographic Envelope (region), Point Style, Datum, Projection and Parameters can be found on the Definition tab.

Layer Projection

To use the GeoCalc Library to correct the Projection for an imported data layer, highlight the layer in the Overlay Control Center and select Options... and Layer Projection to select the appropriate projection for the data layer.

The data layer's current Projection may be corrected or defined from this option, however it is not possible to setup Coordinate Transformations from this dialogue.