The Geographic Calculator supports a number of regional geoid models. These models are based on data tables containing differences between the ellipsoid and the geoid model for a given area. Please be aware that these models are not exact Mean Sea Level values, but are approximations of Mean Sea Level.
Supported vertical transformation types are available for many localities around the world. If the grid files for a particular geoid are not available for download through the Datasource dialogs, please contact Blue Marble Geographics' technical support for information on the availability of a particular grid.
Recently added support for the following transformations:
GGXF Dynamic and Static Geoid Models
1This function has been added as part of the NOAA National Geodetic Survey NSRS and Canadian Geodetic Survey CSRS modernization (e.g. NATRF2022); see NGS Beta Products for more information.
NGS modernization product GEOID2022 includes both a static geoid and a dynamic (time-dependent) geoid for transforming between ITRF2020 EH and NAPGD2022.
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GGXF Geoid Model - The static geoid is a gridded dataset representing the baseline geoid undulation (in meters) anchored at the fixed reference epoch.
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GGXF Dynamic Geoid Model - The dynamic geoid includes not only the baseline geoid undulation but also the linear time rate of change in undulation (meters/year) caused by Earth’s mass redistribution. To use the Dynamic Geoid, ensure that time-dependent transformations are enabled in Options > Preferences, and specify the survey epoch (date of observation) on both the Source and Target date fields on job in Geographic Calculator (i.e., the same date must be entered in both Source and Target fields to enable the transformation).
Additional supported formats:
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Geographic3D to GravityRelatedHeight (Gravsoft) [EPSG 1047] - Gravsoft format (.gri, .gra) developed by DTU Space (Denmark) for the Gravsoft gravity and geoid processing suite.
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Geographic3D to Depth (Gravsoft) [EPSG 1109] - Gravsoft format for depth-positive output.
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Geographic3D to GravityRelatedHeight (ISG) [EPSG 1117] - ISG Format defined by the International Service for the Geoid (Politecnico di Milano, Italy) for standard ASCII geoid grids.
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Geographic3D to GravityRelatedHeight (NRCan byn) [EPSG 1060] - Binary format (.byn) created by Natural Resources Canada (Canadian Geodetic Survey).
All transformations show the default type of interpolation used for that method on the definition for that geoid. Newly created geoids will start with the default method selected.
See Also Vertical Grid Shift Files.