[time-nuts] Do ordinary clouds adversely affect GPS reception?

[Fiorenzo Cattaneo]

Hi jimlux -- unfortunately my domain expertise is in the digital
domain (computer science) and I'm having a hard time in following this
paper. I do understand that "space weather", i.e. CMEs (coronal mass
ejections) will significantly impact GPS/GLONASS operations when the
charged particles reach earth.

One question I would have for you is on the ionospheric delays due to
weather conditions like moderate or heavy rain, thunderstorms and more
severe weather fronts. My understanding of it is that when it comes to
GPS usage for positioning purposes, the use of DGPS or some kind of
augmentation system like WAAS provides "good enough" corrections to
compensate for ionospheric perturbations. Whereas for timing
applications, using stationary mode (i.e. either manually programming
station coordinates into the GPS receiver or having the GPS receiver
compute them over several hours by averaging out positioning data) is
enough for "good" enough timing measurements.

How much is "good enough" is not quite clear to me. What would be the
magnitude of timing errors with GPS in stationary mode, assuming my
understanding of stationary mode is correct?

My current Oscilloquartz DGPS, BG7TBL DGPS and GPS + Symmetricom BCP
635 timing board setups gives me an estimated best time accuracy in
the order of 5 to 50 microseconds (my own estimate -- unfortunately I
don't have access to a lab with calibrated reference cesium
oscillators), which is enough for my "time-nuts" hobby.

I wonder if I would be able to measure ionospheric delays -- perhaps I
could measure them by comparing the difference of my "well known" GPS
coordinates once Oscilloquartz DGPS locks in stationary mode versus
the GPS coordinates I receive with a UBLOX-7 vanilla receiver?

Apologies for the many questions.

-- Fio Cattaneo

Universal AC, can Entropy be reversed? -- "THERE IS AS YET
INSUFFICIENT DATA FOR A MEANINGFUL ANSWER."

On Tue, Oct 22, 2019 at 6:06 AM jimlux <jimlux at earthlink.net> wrote:
>
> On 10/22/19 1:13 AM, Poul-Henning Kamp wrote:
> > --------
> > In message <CADXevOaQ6a7eUoKciAttXhr5=w5Y6xxYbojFQMRB42x2QPLXfQ at mail.gmail.com>, Fiorenzo Cattaneo writes:
> >
> >> Any kind of atmospheric disturbance has a measurable effect on GPS
> >> space and time precision, [...]
> >
> > Actually, it's even simpler than that:
> >
> > Any electrical charge in the freshnell-zone between the two antennas
> > delays the signal.
> >
> > In practice that means "any ion ..."
> >
> > Rain clouds harbour significant ionization, long before they become
> > thunderstorms.
>
>
> That's still a pretty small effect for RF propagation at L-band
>
> and here's a paper discussing just such effects
> https://iopscience.iop.org/article/10.1088/1742-6596/1112/1/012021/pdf
>
> what happens here is that charge in a large thunderstorm affects the ion
> density in the ionosphere.
>
> However, I don't think that's "cloudy day vs sunny day"
>
>
>
>
> >
> > Apart from that, the lower atmosphere is pretty predictable with
> > respect to ionization.
> >
>
>
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