To ensure the highest accuracy for spatial data, Global Mapper now utilizes the GeoCalc geodetic engine and datasource. This provides a robust framework for coordinate management, featuring an extensive library of coordinate reference system objects and advanced datum transformation methods for professional-grade results. The following guide serves as an introduction to navigating the new datasource and managing coordinate systems in Global Mapper.
Datum Transformations
In versions 26.2 and earlier, Global Mapper used an early-bound system; each datum had a single transformation (routed through WGS 84), which allowed transformations to happen automatically. This simplified the process and provided acceptable solutions for certain applications; however, many of today’s users require the ability to choose particular datum transformations to meet precise project requirements.
The GeoCalc integration brings a library of direct, high-accuracy datum transformation choices including time-dependent transformations, regional grids, and geoid models, in addition to support for user-defined custom objects.
Refer to the table below for a summary of the geodetic enhancements introduced in the current version:
| Transformation Feature | Legacy (v26.2 and older) | Current (GeoCalc Integrated) |
| Datum Transformation Choices | Early-Bound: a single transformation hard-coded to each datum. | Late-Bound: users can view and choose from all the available transformations for moving between the source and target datum. |
| Automatic behavior | Transformation is determined by datum selection (routes through WGS 84 if needed). |
The default Auto-Pick setting uses a multi-stage scoring algorithm to choose the best transformation available by prioritizing direct shifts, area of use, mathematical rigor, and accuracy ratings. In Geodetic Settings, users can select another Auto-Pick option that will attempt to match legacy transformations based on available options in the new datasource. Auto-Pick choices can also be overridden individually or disabled entirely. When Auto-Pick is disabled, transform choices will be remembered within the workspace and automatically used on any additional imports that have the same source datum. |
| Vertical Transformations | Not included (required additional Geographic Calculator license/installation) | Full support of vertical transformations (including geoid models) is available in standard Global Mapper. Assigning a vertical coordinate system in Configuration is optional; if none is assigned, no vertical transformation will be applied. |
| Time-dependent transformation | Not supported | Time-dependent transformations can be enabled in Geodetic Settings, providing full support for methods including Horizontal Time-Dependent Positioning (HTDP), Canadian Velocity Grid (NET), Time-Dependent Helmert, Time-Specific CFR and PVR Transforms, and New Zealand Deformation Model (NGZD2000). |
Customization
To maintain geodetic integrity, built-in datasource objects cannot be altered. However, users can easily add custom coordinate systems, datum transformations, and other objects to support their particular projects, such as local low-distortion projections. Additional details can be found on the Edit Datasource page.
Automatic Creation: When loading a file with metadata that doesn't match the stock library, Global Mapper automatically generates a custom coordinate system object.
Creating Custom Objects: If a necessary object is not included in the provided datasource or requires unique parameters, you can manually enter them or create an editable copy of an existing object.
Saving & Sharing: Custom objects are saved to a local library and can be shared with other users via the custom.xml found in the following directory: C:\Users\UserName\AppData\Local\GlobalMapper\VERSION\GeoCalc\custom.xml
Legacy Projection Support
With the integration of the GeoCalc library, Global Mapper now utilizes more precise formulas for coordinate projection. When loading files from version 26.2 or earlier, you may notice updates to certain projections. While most transitions are automatic, some coordinate systems may require manual adjustment or are no longer supported. For a full list of these changes, see Legacy Projection.
Frequently Asked Questions
"Legacy" refers to how the Global Mapper used to behave without GeoCalc Mode enabled in versions 26.2 and older.
Where did the "Projection" section of the Configure dialog go?
The "Projection" section of the Configure dialog has been renamed to "Coordinate Reference System". That section has always encompassed more than the display projection alone, and the new name better reflects that. This change is also present in other dialogs throughout Global Mapper: the word "Projection" in most places has been replaced by the more accurate "Coordinate System" or "System", because it also encompasses datum, geoid, units, etc.
Are all of the projections and datums that were built in to previous versions of Global Mapper still available?
Most of them are, and there is added support for many coordinate systems that were previously unsupported. However, a handful of very specific projections are no longer supported. See Legacy Projection Handling for more information on specific projections that are now handled differently. Overall, Global Mapper can use almost all of the same coordinate reference systems it could before, plus some. There are small differences in how some projections and coordinate systems are described. For example, the previous "Geographic" projection using WGS84 can now be found under Geodetic>World>WGS84.
Is there a way to keep using the legacy behavior from Global Mapper v26.2?
While there is no way to go back to the old dialog, there is an auto-pick setting that will cause Global Mapper to automatically select transforms that are the same as in legacy versions. This can help to preserve compatibility with older workspaces that may not be using the most accurate transforms available.
Are exports from Global Mapper still in the Coordinate Reference System that is specified in the Configure menu?
Yes. The basic workflow to import, reproject, and export data is fundamentally the same: load data, change the Coordinate Reference System in the Configure menu, and then export. The only change is how the reprojection is performed: it now uses a more sophisticated, accurate library, and gives more control over the transform used when necessary.
How is choosing a Projection or Coordinate Reference System different from legacy versions of Global Mapper?
Rather than choose a projection from a long drop-down list, and then set a datum and unit separately, coordinate reference systems are now in a single location that can be easily searched. This means that it may now be necessary to think about the datum before the projection for some systems, even though Legacy Global Mapper could choose them in either order.
Additionally, options to edit specific coordinate reference system parameters such as scale factor, origin latitude, and central meridian are now available using the button to Edit Definition.
Why is a "Grid file download progress" bar appearing?
When auto-pick is enabled in Geodetic Settings, grid files needed for transforms may be downloaded automatically. When this occurs, a progress bar will be visible.
Does Geographic Calculator need to be installed with Global Mapper?
No, the necessary information and tools have been integrated into Global Mapper. However, Geographic Calculator still offers some functions that are not yet available in Global Mapper or Geographic Calculator Online.
Is GeoCalc Mode still available?
No, it is no longer necessary.
How to create and use custom coordinate systems and transformations?
The object definitions that are built in to the GeoCalc datasource cannot be modified. When a file is imported with embedded coordinate system information that does match an existing definition, a new object will automatically be created. For more information, including full steps for how to create a new object, see Edit Datasource.
Are the datasource in Global Mapper and the datasource for Geographic Calculator Desktop connected? Does creating an object in one software make it available in the other?
Global Mapper uses its own separate datasource from the one utilized by Geographic Calculator. Making edits to the datasource used by one application will not apply those same edits to the datasource of the other.
How will this affect workspaces saved in prior versions of Global Mapper?
Most workspaces saved in prior versions of Global Mapper should load normally. If a custom datum or ellipsoid was in use, and that datum or ellipsoid is now built-in, Global Mapper will select it automatically. Any custom definitions that are not currently built-in will be added as custom objects. Some very specific coordinate systems are handled differently than in Legacy versions, however, and it is worth reviewing the information about those special cases if problems occur.
For users who previously had GeoCalc mode enabled, workspaces saved in earlier versions using GeoCalc Mode should also load normally. If a coordinate transformation that used grid files was saved, then the grid files will be downloaded automatically if necessary.
The default transformation selection method when Auto-pick is enabled is to choose the best available transformation for all loaded layers in terms of accuracy. This may not match the legacy behavior, especially in the case of datums that were defined by null transformations to WGS84. If it is necessary to maintain these null transformations between specific datums to ensure consistency with legacy behavior, the Auto-pick option Attempt to Match Legacy Global Mapper selection should be selected, and Allow null coordinate transformations should be checked in Geodetic Settings prior to loading the workspace.
How to apply the extra parameters found in State Plane Coordinate System definitions from legacy versions?
The extra parameters for State Plane Coordinate Systems applied an additional transformation on top of the built in State Plane Coordinate parameters. This can still be performed by loading in the data associated with the built in State Plane Coordinate System Definition, and then in the layer context menu accessible by right clicking on the layer in the control center select SHIFT - Shift Selected Layer(s) a Fixed Distance or Transform Coordinates ..., choose Specify Coordinate Transformation in the Select Transformation Type dropdown menu, and enter the parameters.
How do I write a vertical datum into the header of a .las/.laz file?
The currently active vertical coordinate reference system set for the workspace will automatically be written into the file header of exported LAS files.
How do I change the projection and datum now?
The process to reproject and apply transformations to data is outlined on the Supported Coordinate Systems page. In general: go to the Coordinate Reference System section of the Configure menu, select a new coordinate system, and then click Apply.
In legacy versions (26.2 or older), the projection could be changed independently of the coordinate reference system and datum. Now, the projection and datum are tied to the horizontal coordinate system definition. An existing horizontal coordinate system needs to be selected that includes the specified projection or datum, or a new custom object needs to be created. More information can be found on the Edit Datasource page.