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    Re: Any practical Method to obtain WGS84 Altitudes?
    From: Antoine Couëtte
    Date: 2024 Jun 6, 05:41 -0700

    Hello to all,

    1- Further to my research to obtain - hopefully reliable - WGS84 Altitudes I have not found any better and consistent way than the following procedure:

    1.1 - For any given sufficiently known point / landmark obtain its 3D Coordinates - thus including its AMSL Altitude - from the web, e.g. from wiki.

    1.2 - Then use the EGM08 [height] approximation to obtain the Geoid elevation above the WGS84 Ellipsoid at such specific Coordinates.

    1.3 - Add the EGM08 height to the AMSL Altitude in order to obtain the Elevation above WGS84.

    2 - All this is summarized in the attachment which can also used for future comparison reference when "better" tools can be found.

    2 - Better tools ?

    The WGS84 referenced altitudes are nothing but the "raw" GPS Altitudes which were once available as such to the Internet community.

    Meanwhile, such GPS Altitudes seem to have been reprocessed in some inconsistent ways  - [almost] unknown to the regular/standard/ non professional end-users - regarding the altitudes corrections applied to the WGS84 raw/initial data (which corrections exactly ?).

    Again check the attachment where the GEP Altitudes (GEP: Google Earth Pro) are totally inconsistent worldwide with either the AMSL or the WGS84 referenced altitudes.

    On another hand as lateral thinking and to the best of my knowledge, Galileo, Glonass and Beidou also use WGS84 as their satellites reference mainframe. Do they publish such WGS altitudes available to all ? Any light shed here will be most welcome.

    3 - Last

    Onto my Laptop (Windows7 Pro, 64-bit SP1, 4.0 GB Ram), I have downloaded the file mentioned in (2.2) of the enclosure, i.e. https://earth-info.nga.mil/index.php?dir=wgs84&action=wgs84 .

    I am unable to launch this software. Am I missing something ? (Program Compiling, decompiling or other ?).

    Any help here will be greatly appreciated.

    Thanks in advance here,


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