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

From: Gary E. Miller
Subject: Re: [gpsd-dev] [gpsd] Altitude in TPV
Date: Fri, 14 Sep 2018 11:36:21 -0700

Yo Gerry!

On Fri, 14 Sep 2018 07:49:58 -0500
Gerry Creager - NOAA Affiliate <address@hidden> wrote:

> > I often put two GPS side by side.  Their lat/lon will agree
> > closely, but their altitude often differ by 20 feet.  I had one $8k
> > GPS that was off by 64 feet!
> >  
> For code-phase receivers, this makes sense, especially for single
> frequency models. Code phase has trouble resolving vertical at much
> better than 3-5 meters, and will bounce around a fair bit.

True, in the recent past.  I have at least two models of newer GPS that
do much better than that.

> multi-frequency carrier-phase postprocessing will resolve centimeter
> heights for HAE. Othometric heights require just a little more
> processing to accomplish.

So I thought.  But my recent practical experience has not shown that.
At least without post processing.

> At least that's the academic version of things.

Yes, academic, not experimental.

> I did some work using
> L1C, and multi- and long-baseline L1/L2 code and carrier phase work on
> orthometric height determination a few years ago.

I have an L1/L2/L5 GPS.  I was expecting great things, but never saw
them for real time measurements.

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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