Gosh I hate to bring this subject here from the main board, but it's been bugging me for long enough. I know without a doubt I've had two sessions marred by "moderate" to "mild storm" solar conditions in the last two months. The first was during the mid August solar "belch". Trying to get the last repeat vector in on a control point some 7 miles away. Waited till well after sundown for 8 sv's with low pdops. Just didn't account for the fact the ionosphere was just lighting up from a solar wind. I now believe a few other sessions have been somewhat corrupted over the last year by the same phenomenon, just can't prove it.

Can anyone give me any reference material to read (in a bit less technical jargon than an astrophysicist) to be able to quantify the effect of solar weather and it's influence on L1 gps. I have followed both the sec/noaa site and the nasa "spaceweather" site daily, if not more often, for two months. I'm beginning to see some relationships in the charts but not sure.
I think in the next couple of days we're going to see some minor solar influenced storm conditions so I'm planning to experiment. I'm going to leave a Locus on my base station post for 10-12 hours, and another a few feet away (just to have two) and check a time line to compare signal to noise ratio with the space weather charts. I don't know if I'll see anything, and if I do I'm not sure I'd recognize it, but what the heck.

Any comments appreciated.


J.D.

J.D.,

I looked through my files, but couldn't find anything basic on solar effects on the ionosphere.

You could always trade up to dual-frequency gear. ;>}

Regards,
Brian

I have been asking for dual frequency for the past six months. Unfortunately, Dad read that the L2 frequency signal is 40% in strength that of L1. Thus he suspects solar events and a highly charge atmosphere would wreak even more havoc on dual frequency than single.

Shawn

PS - Actually, I am quite satisfied with L1. I suppose I would have to work with a dual frequency unit for a while to see what I was missing in order to get worked up about it.

Has absolutely no research been done by gps manufacturers to determine these effects? To at least be able to answer dunderheaded questions like mine?

Still wondering. (or is that wandering)

J.D.

I asked similar questions some weeks ago...From what I learned (by myself), single is better than dual for shorter baselines....Some debated this, but did little to provide proof..The methods for resolving the interger solution was stronger for the single freq vs the dual over short distances..I resolved t his from Strange/Boore (Linear Algebra, Geodesy, and GPS) which took me weeks to decipher...(it's been a long time since college)

From other research...Solar activity affects both L1 and L2 in the same way...
While it affects both the same, you usually dont' have the same time on point when doing RTK versus Static.
It appears from some posts that it affects RTK (the base to rover) signal worse than for a static solution...
My synopsis is that static can properly model most errors in the solar region (within reason) , but that RTK is much more prone to provide incorrect solutions....

PS- From a non-astrophysicist...

Trimbo- From the land of up-under

J. D. (no, not Dunderhead),

Not to contradict the "Man Whose Name Shall Not Be Spoken Here", the short answer is no, because full-bandwidth dual-frequency receivers let us measure and cancel out ionospheric delay. It's the time delay causing trouble with L1 receivers when iono activity is high. Yes, ionospheric activity affects both L1 and L2, but given both frequencies, all but the worst can be compensated for.

Shawn,

I appreciate both your attitude and enthusiasm, but assume J.D. still writes the checks. ;>}

Regards,
Brian
Modified By Brian D. Ewing, PLS on 10/10/2001 at 9:10 PM

I pay in beads and shiny trinkets.

As for the ionosphere, and the ability of L2 to measure/compensate the fluctuations, I can accept that. After giving much thought (ooouuuuccchhhh again) to solar wind from coronal mass ejections, and it's possible influence on the ionosphere, my guess is it (solar wind) can cause a wave or ripple effect in the ionoshpere. I can see this as a problem for L1 especially, depending of course on the frequency (mechanical rather than electrical or radio)of the ripple. I could also see this as having a possible effect, although reduced in magnitude on L2.

But, what about the magnetospohere being lit up in a proton storm. Does this not affect or distort both L1 and L2. Even if it's only L1 effected, I would still like to find out what conditions to be aware of. Admittedly, at 32°21'57.50398 N Lat I ain't gonna see the aroura much. Deral has a much better view than I do. I believe Sky Wilson has a considerable view.

Just trying to figure out (1) If some of my past sessions, with absolutely no apparant reason for failure could have been due to solar induced conditions. And (2), if solar conditions matter, what levels of indicators should I watch for at my latitude. Remember, I'm waaayyy North of Jimbo.

Thanks for the input.

J.D.

Brian, I hope I don't have to get used to bifocular vision, as I don't think I could. They said 4 weeks for most before lasic surgery...I've been 6+ and at least another week before they'll consider final approval to schedule. I don't envy anyone doomed to bifocals.

J.D.,

Re: Iono & dual-frequency
While both L1 and L2 are delayed by active ionosphere (caused by sunspots and solar flares), because we have measurements on both frequencies, we can measure and correct for the delay. Trimbo's quite right that this affects RTK more severely than static. Back in the L2 codeless days, iono could become bad enough that the receiver couldn't track the squared L2 (especially with TID's-Travelling Ionospheric Disturbances), because the conditions were changing too rapidly. Z-series receivers rarely have a problem with this, and won't at your latitudes (above 70 N might be a different story).

Re: Proton flux and magnetosphere
This is an area I don't know much about. Maybe some of the NGS people could give yo9u an answer. I would expect such conditions to add noise, but not cause significant problems.

Can you send me a data set where you were unable to obtain a good solution? I'll take a look and see what the problem might be. Please send to the address in my profile on the Ashtech board, the one on the main board goes to my home. This one is bewing@magellangps.com

Regards,
Brian

Usually, I am sitting under the shade of a big oak tree. I have taken my notes, measured the bearing trees, now I just sit and listen to the buzz of the bees. Maybe I read another chapter of my fovourite book, waiting for the receiver to get enough data for a good observation. I might even take a little nap.

But I dont worry about solar activity. Sometimes I put the solar filter on my big telescope and look at the sunspots, or if I'm lucky a flare.

Arent you just talking about 10 more minutes of acquisition time during unfavourable solar conditions?

I'm afraid solar activity, although it has an 11-year cycle of sorts, is just plain unpredictable. Oh, bother.

One thing all of you are overlooking is multipathing from "space junk" think about it! There is so much crap in the atmosphere that you can't even imagine. A good friend of mine works for NASA and says that we never hear about all the stuff the shuttle hits. One episode he recorded personally included the collision to get this "a volkswagon beetle bug" It was sent to space as some kind of experiment by the Soviets in the late 60's. GPSOUT late
Modified By gary kuroski on 10/16/2001 at 1:00 PM

Gary

Guess it's gonna take more than aluminum foil to shield us from VW's.

The Germans had a rocket, called the V2..The russian spy garbled up some data when sending it back to Moscow...Hence the VW Rocket...

Better take lots of foil...Plus-It might even still be running when it hits the ground..