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    How-to Create a Geoid or Vertical Offset Model (VOM)

    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.

    See Questions & Answers for more in formation.
    Also for items with an asterisk *.

    Related pages:

    Geoid model decision chart

    Questions & Answers

    SubjectQuestionAnswer
    ProjectedWhat is projected data?We assume that this is projected on project datum and the separation value is also relative to project datum.
    Point spacing

    What is regular and irregular spacing?

    Irregularly spaced:

    Regularly spaced:

    What is meant by having a different spacing in x and y?The data can be regularly spaced but still have a different spacing in X and Y.
    Area sizeWhat is a small area?

    This is a bit tricky since it mostly depends on points in an area:

    • If you have an ASCII file that covers the whole continent or more, for example, it is recommended to use the BIN workflow.
    • If it just covers your work site, using a QGFVOM is recommended.

    If the QGFVOM is larger than 15MB it is also a good indication that you might need to use either a smaller area or try the BIN workflow.

    DatumWhat is Project datum and Source datum?

    Example of geodetic setup:

    Project datum: ED50
    Source datum: WGS 84

    Purple steps

    		What do they refer to?

    Storage locations

    		Were are the different types of geoid model files stored?
    SourceTypeFormatFile LocationAdditional information
    QPS installersGeoid ModelsBINC:\Program Files (x86)\Common Files\QPS\Geo\GeoidAll (pre-defined) Geoid BIN files installed by Qinsy
    using the separate QPS Geodetic Package 3.0.x installer
    Created by userGeoid ModelsBINC:\Users\Public\Public Documents\QPS\Shared\Geo\Geoid

    Geoid BIN files (Lat/Long and E/N),
    Created from a Sounding Grid exported as Geoid Model

    Vertical Offset ModelsQGFvomProject folder\Geoid

    Vertical Offset Models (VOM) in *.qgfvom format as created in the Survey Manager

    Previously: River Line Model and VORF models in PRO format

    QGFVOM VS BIN

    		What is the advantage of one format over the other?

    		QGFVOMBIN
    Used in all QPS software(tick)(tick)
    Use for large areas(error)(tick)
    Irregularly spaced points(tick)(error)
    Regularly spaced points(tick)(tick)
    Datum (ellipsoid) aware(error)(tick)