On Wed, Jun 26, 2019 at 6:20 PM Eric H. Christensen via Talk-us <[email protected]> wrote: > I was told there was a website that forecasted the best times to do survey > work with GNSS based upon diversity of satellites in the sky, solar activity, > etc. Does anyone know what site this is?
Nowadays, the constellations are dense enough (particularly if you can use GPS/GLONASS/Galileo/BaiDou) that a consumer-grade GPS receiver is unlikely to see a difference based on satellite diversity. (It's different, possibly, if there's a failed satellite and no on-orbit spare, or the on-orbit spare hasn't been moved into position, and there the sites like https://www.gnssplanning.com/ will give you useful information.) The GPS signal is more stable by night and in clear weather. A bigger effect is signal absorption. There's one trail near me for which my mapping involves considerable guesswork, because there's dense coniferous tree coverage (nothing viisible even in winter aerials), and the trail goes down into a couple of itty-bitty slot canyons where all the sky that the receiver can see is directly overhead, and a little patch to the north where the satellites seldom cross. There are also cliff faces that set up nice reflections of the RF signal, so sometimes the receiver's computed position is false. It's pretty wonky. I bet I could control the effects by using a survey-grade GPS receiver, setting it on a solid tripod, and giving it an hour or two of integration time, but I don't have such a device, nor do I have the time to do that for each trackpoint. Space weather is another significant effect, but right now we're close to sunspot minimum, and space weather is mostly quiet. https://www.swpc.noaa.gov/ provides forecasts. https://www.swpc.noaa.gov/products/alerts-watches-and-warnings alerts to significant conditions. https://www.swpc.noaa.gov/impacts/space-weather-and-gps-systems gives an idea what to look for, and https://www.gps.gov/cgsic/meetings/2012/comberiate.pdf is a more advanced discussion of the same thing. The bottom line here for the Lower 48 + Hawai`i is probably 'don't worry about it unless Kp gets above about 5 or there's a class M or X flare in progress.' _______________________________________________ Talk-us mailing list [email protected] https://lists.openstreetmap.org/listinfo/talk-us
