How to add Datum NAVD 88?

naominchnaominch Global Mapper UserPosts: 2
edited May 2015 in Elevation Data
I am very new to use global mapper. I want to add NAVD 88 datum. Is there available date to load for it?:confused:



  • Ice Age MarkIce Age Mark Global Mapper User Posts: 294Trusted User
    edited May 2015

    As I understand it (which may, or may not be entirely correct) Global Mapper doesn't do vertical datums. The "datum" option on the projection dialog is for horizontal datums only. GM loads each separate elevation data layer with that file's "zero" as mean sea level, or 0 ft/m above sea level. That's it. You can make the adjustment from whatever the elevation file source says is it's datum to NAVD 88 by using the "alter elevation" tab for the layer.

    Theoretically, you could use the "combine terrain" function, and combine an elevation layer with a digital "geoid", or a digital map of the NAVD 29 - NAVD 88 adjustment, or both; but I haven't done this yet. There would likely be some resolution/resampling issues with that.


  • bmg_bobbmg_bob Global Mapper Programmer Posts: 1,970
    edited May 2015

    In order to use vertical transformations in Global Mapper, you would have to also have our Geographic Calculator product. Global Mapper can integrate with Geographic Calculator to allow you to work with geoids (including NAVD88) for vertical data.

    For more information: Geographic Calculator


  • naominchnaominch Global Mapper User Posts: 2
    edited May 2015
    Hi Bob and Mark,

    Thank you for your comments. It's very helpful understand about meaning of zero. We might need to think about buying geographic calculator.

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