Long delayed response (work got in the way of looking at hobby-related emails...)
On Fri, Sep 14, 2018 at 1:38 PM Gary E. Miller <
address@hidden> wrote:
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.
In this case, the academic version was based on a field program and rather rigorous analysis. Some of my work eventually was utilized by the National Geodetic Survey.
I have an L1/L2/L5 GPS. I was expecting great things, but never saw
them for real time measurements.
Not so much in code phase. Long term averaging of data collected at a fixed interval (e.g., 10-30 sec) then decimated would give a better representation. We can talk about the need to decimate if you'd like.
Regards
gerry