Manage geoid models

In Eye4Software Hydromagic Survey or Dredging, a geoid model is used to calculate the separation between the local vertical datum and the WGS84 ellipsoidal height returned by the GPS or RTK receiver. Each geoid model is in fact a simple binary file containing separation values in a regularly spaced grid.

The geoid files have the file extension ".geo" and are stored in the "\ProgramData\Hydromagic\Geoids\" folder on your hard drive. To access the "\ProgramData\Hydromagic\" folder, please select the "Open Program Data Folder..." option from the "Help" menu.

To open the "Manage Geoids" window, select the "Preferences" option from the "Options" menu, and select the "RTK" tab. By clicking the "Select..." button you can access the list of geoid definitions currently used in the software. Using "Select Geoid Model" tool, you will be able to add new, remove or alter geoid definitions in the built in database.

Please note that not all geoids are installed by default. Geoid models that are configured, but not installed, are displayed in red. These geoids can be downloaded from our website: http://www.eye4software.com/hydromagic/documentation/geoid-models/, or right click one of the red items and select "Download and install..." to download a geoid automatically when you are connected to the Internet.

Select the "Download and Install" option to
install a geoid from the web automatically.

Geoid list

When clicking an item in the list, its parameters are displayed below the list. You can edit these parameters by clicking the "Modify" button. A geoid model is displayed by the flag of the country where it applies to. If a geoid model applies to multiple countries or regions, a globe is displayed.

Select a geoid model to show or alter its properties.

Deleting a geoid

You can delete any geoid definition, by selecting an item from the list and clicking the "Delete" button. The software will show a popup to confirm that you are sure you want to delete. When clicking "Yes" the geoid will be deleted.

Modifying a geoid

You can modify a geoid by clicking the "Modify" button after selecting a geoid from the list. After clicking the button, the text on the 'OK' button will change to 'Save'. Clicking the "Save" button will save the modifications, clicking "Cancel" will keep the old data.

Adding a geoid

To add a new geoid model, click the "Add" button. When adding a new definition, it is required to specify a name for this geoid, as well as the geoid file to be used. Geoid files can be downloaded from our website, or generated using our EGM2008 utility.

Using the Geoid Conversion utility, which is a freeware tool that is shipped with the Hydromagic software, you can convert some geoid file formats to the format used by Hydromagic. Geoid file formats that are supported include:

• Trimble Geoid File Format (GGF Files);
• Carlson Geoid File Format (GSF Files);
• US National Geodetic Survey (NGS) File Format (BIN Files);
• Natural Resources Canada Files (BYN Files);
• Surfer V6 Binary Grid Files (GRD Files);
• ASCII Geoid Files.

When using the Geoid Converted, place the generated ".geo" file into the Geoids folder and add the geoid definition manually.

Selecting a country is not required, but the country can be used to sort lists by country, if the geoid does not apply to a simple country, just select "Earth", "Europe", "Asia" etc... Click the "Save" button to store the newly created geoid model, by clicking 'Cancel,' the input is ignored and you will return to the list.

Video tutorial