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 <jim...@earthlink.net> wrote: > > On 10/22/19 1:13 AM, Poul-Henning Kamp wrote: > > -------- > > In message > > <CADXevOaQ6a7eUoKciAttXhr5=w5y6xxybojfqmrb42x2qpl...@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. > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.