Re: [gpsd-dev] [gpsd] Altitude in TPV

[Gary E. Miller]

Yo Peter!

On Thu, 13 Sep 2018 23:03:37 +0000 (GMT)
Peter Liu <address@hidden> wrote:

> ECEF is nice. I wish I can get ECEF from the INS.

Then it would be a GPS.  :-)

> Regarding MSL vs. Height Above Ellipsoid (HAE). I always like to go
> back to the point MITRE's Mike Butler makes in the "Developer's Guide
> to Cursor on Target CoT)"
> http://www.dtic.mil/dtic/tr/fulltext/u2/a637348.pdf

Well, in the GPS lexicon, as your paper points out, MSL is the HAE.

I like the guys writing style.

For the reasons he noted, GPS people gladly ignore old notions of MSL
and implicitly replace it with HAE.

Now if we could just all agree on which ellipsoid and how to
calculate it...

    GPS uses WGS 84 (but it used to use ITRF2000)
    GLONASS uses PZ90.11 (but used to use PZ90.02)
    GALILEO uses GTRF
    BeiDou uses CGCS2000

And, just for fun, my local official city and county maps default to
WKID 102100, but also support NAD 83 and WKID 4326.  

Luckily WKID 4326 is just a convoluted way to say EPSG:4326 and WGS 84

This rabbit hole is deeper than it looks...

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

            Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin

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