Differential procedures nearly eliminate the dtrop contribution and the wet component contribution becomes trivial.
I'm under the impression that the "heavy cloud cover" problem crops up when the base is subject to it and the rover isn't, or vice versa.?ÿ But since I pretty much never see those conditions where I work, I've never bothered to investigate.
I run mine in the rain fairly often. Both base and rover are in the same rain, and are usually less than a mile apart. This shot above is from a topo, and I'm in dense woods. If elev is within .3 here, it's plenty good. It's raw dirt.
I've got a little bonnet for the LS that allows me to work too. But, I get wet!
I think the idea of D-GPS applies here.... Differential GPS that is. That is, the DIFFERENCE in environments. For base and rover. But, when they are near each other, it self-mitigates.
Enjoy being a surveyor. I do.
Nate
In my experience what I stated is undeniably true.?ÿ But considering your theory, if the dry component can be modeled in a few seconds or minutes, but the wet can not, then would the wet component not be more of a problem??ÿ I don't know, the textbooks say the troposphere and local multipath are basically the only remaining challenges.?ÿ Sometimes I don't even bother going out if there's low thick clouds anymore, because i know it will take much longer than normal to get acceptable solutions.?ÿ It's also known that water is a major contributor to signal interference.?ÿ
Sorry to disappoint you you but it's not my theory ????;?ÿ I'm merely parroting what I read in technical papers and journals.
If by stating "water is a major contributor to signal interference"?ÿyou mean signal attenuation, that is clearly not the case.?ÿ Atmospheric attenuation is dominated by oxygen?ÿin the 1-2 GHz band and is very small, about 0.035dB at zenith and about 0.38 dB at 5 degrees elevation angle.?ÿ The effects of water vapor, rain, and nitrogen attenuation at L-band frequencies are negligible.?ÿ Worst case heavy rain attenuation is very small, for even dense rainfall (e.g., 10 cm/hour) it's less than 0.01 dB/km.?ÿ The GPS frequency bands were selected specifically to minimize atmospheric attenuation.
I'm puzzled concerning why in your experience using Javad under low thick clouds is so difficult given that in my experience (Trimble, Leica) cloud cover had no discernable effect on accuracy or time to fix.
@mike-marks I'm parroting also, but would have to look it up again to get more particular:)?ÿ I looked into it wondering why more difficult under pines than broad-leaf, and found references the water being the problem and that pine needles something like 98% water.?ÿ Could be wrong.
I was not commenting on any particular brand, rather on the suitability to achieve less than a tenth repeatability in difficult conditions.?ÿ More geared toward the skeptics part.?ÿ GNSS has made some impressive gains over the past 5-8 years.?ÿ Those holding back because thinking it will not work should really take another look at what's possible now.
As to clouds, it could be as Jim Frame mentioned.?ÿ I use mostly base/rover and it seems to help.?ÿ I'm not a meteorologist, it seems one type of very localized low heavy cloud cover, can see the results as they come in, pass over, and move on.?ÿ Could be unique in some way, just east of great lakes and tug hill plateau. Not noticeable in other conditions, even rain or snow. I don't think I'm imagining things, but I do spend an awful lot of time alone in the woods.
I looked into it wondering why more difficult under pines than broad-leaf, and found references the water being the problem and that pine needles something like 98% water.
Oh yes, 1 mm liquid of water is enough to stop a GPS signal or at least reduce greatly its strength. Indeed, with this amount of liquid water, the C/No is lowered by about 9 dB and the tracking becomes hardly realizable [Gernot, 2009].
I'm under the impression that the "heavy cloud cover" problem crops up when the base is subject to it and the rover isn't, or vice versa.?ÿ But since I pretty much never see those conditions where I work, I've never bothered to investigate.
No need to rub it in our faces.
Sincerely,
Your PNW and Alaska friends.
I wish rain/snow would make the dang thing stop working. Although, early on we discovered our rain events usually came with that electrical stuff which is a no-go. But, not from an accuracy standpoint, our base/rover set-ups have not been impacted by weather that way. On this board there seem to be many complaints concerning accuracy using VRS networks, maybe weather is a reason.
Duane just tells his wife that stuff about it not working in the rain, or even clouds..... 😉
N
@nate-the-surveyor Clear skies in fishing season brick the thing.