Supported Coordinate Systems

Global Mapper v27.0 now includes GeoCalc, Blue Marble's geodetic engine and datasource. GeoCalc is an extensive geodetic parameter database with definitions for many coordinate reference systems, datums, and both horizontal and vertical transformations. This integration provides users with increased accuracy and additional functionality.

A detailed explanation of the changes in v27.0, including an FAQ section, can be found on the Coordinate Reference System Updates in v27.0 page.

Additional information about Coordinate System Support can be found:

Configuration menu - The "Projection" tab is now labeled "Coordinate Reference System" and provides additional functionality:

Edit Datasource - Create new objects or editable copies of existing objects.

Geodetic Settings - Control which types of datum transformations will be available for user selection or chosen by the default Auto-Pick for Coordinate Transformations.

Searching the Datasource - Navigate the interface to choose a new coordinate reference system, datum, etc.

Time-Dependent Transformations - New to Global Mapper, time-dependent transformations provide a means to calculate datum transformations based on movements of the Earth's crust over time.

For a list of browser-based list of available coordinate reference systems and transformations available in Global Mapper, use the Search tool in Geographic Calculator Online. Note that the website can be updated more frequently than Global Mapper. If a system has recently been added to Geographic Calculator Online, and is not yet built into Global Mapper, it can be added by Editing the Datasource.

 

Global Mapper Legacy Projection Information:

FAQ page: Additional details on changes to Projection Handling in v27.0

Legacy Projection Handling: Special Cases

Legacy Projections (reference only)

Legacy Datums and Ellipsoids (reference only)

 

How to change the Coordinate Reference System (Reprojection and Datum Transformation)

Changing the Coordinate Reference System (CRS) in the Configuration menu:

  • All loaded data in the workspace will use this coordinate reference system.
  • All exported files will use this coordinate reference system (unless the particular file format requires a specific CRS).

To change the coordinate reference system of all loaded data, open Configuration > Coordinate Reference System tab and choose one of the following:

  • Use the Search by EPSG Code button to quickly apply a known system.

  • Click the Select Coordinate System icon to search the Geodetic and Projected coordinate systems to find the desired CRS.

  • Click the Edit Current Coordinate System Definition icon to create an editable copy of an object (for changing the parameters or datum that a projected coordinate system uses)

If a layer's native geodetic datum is different than the workspace coordinate reference system datum, a datum transformation will be selected and applied to the layer via the default Auto-Pick setting, which selects the most accurate transformation available based on several criteria. Auto-Pick can be disabled in the Geodetic Settings dialog within the Coordinate Reference System tab in Configuration. The transformations for each layer can be viewed (and changed if desired) at the bottom of the dialog. If the layer and workspace datum are the same, the text "No Transformation Needed" will display.

To define a layer's source coordinate system, use the Layer Coordinate System tab in Layer Options. This does not reproject or transform data, but changes how the source coordinates contained within the layer are interpreted. This option is typically only necessary when the metadata or header CRS information is inaccurate, has been incorrectly interpreted, or to specify the vertical coordinate reference system.

 

PRJ format

There is an Advanced Option on the General tab of the Configuration dialog allowing the older ESRI PRJ format to be exported instead. If for some reason a WKT-representation of the projection cannot be generated, the old ESRI PRJ format will be written out instead.