In response to a question on the other board, I downloaded a 24 hour 30 second RINEX from my nearest CORS, LUMT.
One of the things I look at is the ratio of L1 to L2 observations. The normal ratio is centered around 1.283333, which is the ratio of the L1 to L2 wavelengths, 1575.42 MHz to 1227.6 MHz. They never match exactly because the different wavelengths have slightly different speeds through the atmosphere. Atmospheric variations cause greater delays in the L2 signal and that must then be corrected for precise positioning.
These are the ratios I see for 11 satellites observed at 2011 02 15 0 0 0.00
G22 1.306842
G20 No L2 observed
G30 1.453436
G14 1.432457
G32 1.776299
G12 1.698331
G31 1.369012
G16 No L2 Observed
G25 1.372810
G24 0.541627
G29 -4.963407
All I can say is I have never seen numbers like G24 and G29 gave, but I would say they are out of range of any correction algorithm. Once filtered the remaining 7 satellites may give a reasonable position.
Paul in PA
Damn solar weather!
We did some static obersavtions with 6 Locus (L1) units running all at once on the 15th. I obviously can't compare the L2 data, but measureing conventionally between intervisble points yielded terrible (+/-0.2') results. Looks like we'll doing a "do over".
>> Atmospheric variations cause greater delays in the L2 signal and that must then be corrected for precise positioning.
Better would be to say "Atmospheric variations cause greater delays in the L2 signal which, when widelaned with the L1 signal, partially removes ionospheric errors." The different iono delay rates of the two signals is a good thing.
A uniformly greater delay would be a good thing. But that was all over the place.
Paul in PA
Thats why i hve a site base always RTK & static
You think it's related to solar? From what I've heard, nothing has been strong enough yet to affect GPS. Did nearby CORS show similar data?
Sat Al, The Data Was From A CORS, ''LUMT''
Excuse me but solar flares affect the atmosphere, hence the differences in normally expected delays. Now a really big flare can totally annihilate GPS signals, but what I have shown is probaly the extremes of data that might give a solution, however imprecise.
Paul in PA
Sat Al, The Data Was From A CORS, ''LUMT''
Yes, I saw the data was from LUMT, but I'm wondering if it was an anomaly with LUMT or if it was across the region.
From what I've read, solar flares don't directly impact GPS. A solar flare is not the same as a Coronal Mass Ejection (CME) which can disrupt your GPS units operation.
Interesting.
Excuse me but solar flares affect the atmosphere, hence the differences in normally expected delays. Now a really big flare can totally annihilate GPS signals, but what I have shown is probaly the extremes of data that might give a solution, however imprecise.
Sat Al, The Data Was From A CORS, ''LUMT''
Monday night's storm produced both a big solar flare and a Coronal Mass Ejection. Wdespread satellite or communications disruption, however, is likely not in the cards.
GPS was not technically disrupted since the signals got through. However, the quality of those signals was seriously jeopardized.
Paul in PA
Sat Al, The Data Was From A CORS, ''LUMT''
I don't know, that's a pretty bold conclusion with an extremely limited amount of data.
However, the quality of those signals was seriously jeopardized.
