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How-to Create a Geoid or Height Correction Model (v9.0)

This How-to describes step-by-step how to create your own geoid model file or height level correction model and use it within Qinsy using a file with latitude-longitude-height values.


Qinsy offers the following options to create a Geoid or Height Correction Model using:

Importing ASCII points into Vertical Models file (QGFVOM)

  1. Open the Survey Manager
  2. In the Project Explorer tree - Vertical Models: click with right mouse button
  3. Click New

  4. The New VOM Wizard will be started

    Use the browse button [ ... ] to select the file containing the separation data.

  5. A regular Windows search window opens.
    Select the file type you wish to import.
    The most likely import is an ASCII points file, which we will work with in this example, but other import files are supported as well.

    Select the file to use and press 'Open'

  6. Either select one of the standard layouts of the to-be imported file using the drop down menu,

    or use the browse button [ ... ] to open the Layout Editor where manual options can be entered.
    Either continue with step 6, below, or continue to step 7.

  7. This dialog can be used to indicate the specific layout of the file to be imported

    Paste a line of your file in the 'Example' field and press 'Test'.
    The data as it will be stored in the VOM file will be shown in the 'Output' field.

  8. In this window the Geodetic Parameters can be changed.

    Press 'Next' to continue to the next page of the wizard, press the arrow button at top left to return to the previous page.

  9. Only when a boundary file is available the 'Use a boundary' option needs to be activated

    Press 'Next' to continue to the next page of the wizard, press the arrow button at top left to return to the previous page.

  10. Leave this option activated so no unnecessary triangles are created in the DTM.

    The Link angle and Link distance are set in the Processing Manager's - Ribbon Tab File - Options - Link Settings menu but can be overruled here.

  11. Type in a name for a new file or use the browse button [ ... ] to select an existing file.

    Choose a color map to show the height variations in the offset model.
    Height accuracy: this value represents how accurately the height difference was determined.

  12. This page shows all the settings as entered in the previous wizard pages.

    Press 'Start'

  13. The VOM has now been created

    Press 'Save output' if you would like a log file record of the process.
    Press 'Finish' to close the wizard.

  14. The new qgfvom file is listed in the Project Explorer window under Vertical models.
    A GEOID AREA and GEOIDPOINTS layer are automatically created. 

  15. The layer GEOIDAREA contains the outline of the imported points.
    The layer GEOIDPOINTS contains the VOM in color.

  16. The model is visible in the Plan View.
    If it doesn't display right away, then right mouse click on the GEOIDPOINTS layer and select 'Zoom to fit'.

  17. To check whether the links between the points are to your satisfaction, the grid can be switched off:
    - Select the vertical model in the Project Explorer tree
    - Right click on it
    - From the menu select 'Color scale settings'
    - For Color map select <No color map>
  18. The DTM links are now shown

    Use the right mouse menu again to return to the color scale used earlier.

  19. The model is stored in the Geoid folder of the project or support project.

    Surveypoints, Geoidpoints

    The Vertical Offset Model is like a 3D model which can be checked by drawing Quick Profiles in the 2D Plan View.

  20. In the Console - Open the Geodetic Configuration Overview - Set up the Geoid Height Model - In the drop down menu the predefined Geoid Height Models can be selected.
    There you can select the Vertical Offset Model as created in the Survey Manager.

    Surveypoints, Geoidpoints

    The Vertical Offset Model is like a 3D Design model and can be imported into a Sounding Grid to check if the model does not contain strange features. The best method to do this is currently under investigation.
    From there it can be exported as a geoid model separation grid, which creates an XML file and a BIN file, stored in the Public Shared files. This makes it available for other projects as well.
    See tab 'Use in QPS software'.