Geodetic Settings
The button to access the below listed Geodetic Settings can be found in the Configuration menu, in the Projection tab.
General
Show deprecated geodetic definitions
This setting shows deprecated objects of all applicable types under Edit Datasource. It allows for the selection of deprecated coordinate systems, transformations, and units, when applicable. If unchecked, they will also be excluded from considering by Auto-Pick.
Coordinate Reference systems
Specify coordinate system when creating new layer
When this option is unchecked (default), new layers will automatically be assigned the workspace projection, as specified in the Configuration menu.
Enable this setting to instead be provided with a pop-up to specify the coordinate system each time a new layer is created.
Coordinate Transformations
Use Auto-Pick for coordinate transformations
When this setting is active, transformations will be chosen automatically rather than prompting each time they are needed. Global Mapper will attempt to either match legacy behavior, or choose the most accurate transformation available based on a series of criteria. For more information, see Auto-Pick for Coordinate Transforms.
Choose a logic for Auto-Pick to follow:
Filter coordinate transformations by area of use
Area of Use
Area of Use - Coordinate transformations are often developed to best represent a specific area or part of the world. This Area of Use, or applicable extent of an object in the datasource (such as a coordinate reference system or transformation) can be defined as a polygon or a minimum bounding rectangle.
When enabled, only Coordinate Transformations within the data’s Area of Use will be present in the picker, or selected by auto-pick.
When disabled, Coordinate Transformations will be shown in the picker without checking for area of use, and Auto-Pick will not consider Area of Use when selecting Coordinate Transformations.
While this filter helps limit the search to only include relevant coordinate systems and transformations, some Areas of Use are defined in very restrictive ways. If some expected transformations are not appearing in search, it could be because the data is outside of their Area of Use, even if by a small margin. In that case, turning this setting off will make them selectable.
AOU Bounds:
- Use minimum bounding rectangle - Similar to the layer bounds, the MBR is the smallest rectangle possible that contains the entry's polygon. These are typically broader than the polygon and can include areas just outside of the polygon.
- Use polygons - the default Area of Use.
AOU Containment:
- Data is fully contained - When this option is selected, transformations will only be available if the data is entirely within the Area of Use.
- Data intersects bounds - This is the default setting. When it is selected, transformations will be available if any part of the data intersects with the Area of Use.
Enable time-dependant transformations
Time-Dependent Transformations provide a means to predict and adjust for horizontal datum transformations related to movements of the Earth's crust over time.
If unchecked, date fields will not display.
Time can be set or viewed per layer in the Layer Projections tab.
Allow 3D horizontal transformations to affect height
Uncheck this option to leave Z values unchanged, instead of allowing them to be altered by 3D transformations. This is useful when performing horizontal time-dependent transformations, which can alter Z values if this box is checked.
Allow null coordinate transformations
This setting allows for “None” to appear in the Coordinate Transformation picker. When this setting is enabled, a user may select “None” rather than a transformation anytime a picker appears. It also allows for “None” to be selected automatically by auto-pick in the case that two layers do not have a coordinate transformation going between them.
When this setting is disabled, “None” may not be selected by the user. Auto-Pick will also not be able to select “None”, with the exception of when the unknown vertical coordinate system is in use.
If this setting is disabled but “Use Null Transform for ‘Unknown Vertical’” is enabled, then none will still be automatically used for transforms involving the Unknown Vertical Coordinate System.
Use null transform for "Unknown Vertical"
Allows a null transform to be used when the vertical coordinate system is unknown. This setting will not be affected if the “Allow null transformations” setting is disabled.
Disabling this setting does not prevent the use of None for transformations involving unknown vertical coordinate systems, it just makes it so Null is not automatically selected.
Enable "via intermediate" category
This setting allows for generated transformations to be available in the coordinate transformation picker. If there is no direct transformation between two chosen coordinate systems, when this option is enabled, Global Mapper will attempt to find transformations through an intermediate Coordinate system.
Uncheck this option to disable that search. When this setting is disabled, no generated transformations will be available, and indirect shifts will not be considered.
Automatically download missing grid files when needed
Some datum transformation definitions require additional horizontal or vertical grid shift files that are not downloaded with Global Mapper by default. When these files are needed, and if this setting is enabled, Global Mapper will automatically download the files for use. A progress bar titled Grid File Download will appear during file download.
When manually choosing transformations:
Coordinate transformations that require grid files to be downloaded are in red. When this setting is enabled, double-click a CT to download
When Using Auto-pick:
When this setting is disabled, auto-pick will only select transformations that are already downloaded, as Global Mapper is unable to download the transformations automatically.
Click OK to apply settings changes.