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Re: DTM sentence and Russian datums in US phones (yes, that's clickbait!

From: Gary E. Miller
Subject: Re: DTM sentence and Russian datums in US phones (yes, that's clickbait!)
Date: Thu, 5 Aug 2021 13:24:57 -0700

Yo Greg!

On Thu, 05 Aug 2021 16:10:36 -0400
Greg Troxel <> wrote:

> Greg Troxel <> writes:
> > Over at GPSTest (and Android program for telling you what your GNSS
> > chip is doing), people report that some phones have strange
> > elevations, and digging in there appear to be be two notable
> > oddities:  
> Google actually commented on a bug and (per the GPSTest tracker):

You'd think this would not be a surprise to them...

> >   geoid models that are wrong to a degree even more surprising than
> >   u-blox's reporting of -33m when it should be -29m.  
> It seems the qualcomm chips have 10x10 degree geoid models due to "ROM
> constraints".  My guess is further that it's EGM96, but that's me
> guessing.

"There's many a slip 'twixt the cup and the lip

geoid.o is about 184kb unstripped.  It does geoid, and magvar, to 5x5.
And it does a bit more.

No reason that could not just be in the android image.  No need to trust
Qualcomm to eventually get it right.  And then it can be updated.

But, of course, Android and Qualcomm prefer planned obsolesence.

> >   a DTM statement that says positions are in PZ-90, the grame used
> > for GLONASS.  
> In theory this will be fixed in the december update.

I'll put $20 against that.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703  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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