GPS signal under threat - A few years of reduced precision might affect scientists worldwide.

Nature News ^ | 21 May 2009 | Lucas Laursen

[neverdem]

Click for a larger image to open in a new window. GAO

[gondramB]

>>GPS signal under threat - A few years of reduced precision might affect scientists worldwide. <<

To heck with scientists - they can guide be the stars - what about my Lincoln?!

[org.whodat]

LOL, posted last week, has more to do with budget negotiations than fact.

Anyway, a back up system using cell phone towers is already in the works.

[Star Traveler]

Well..., my GPS usually shows it’s picking up around six or eight of those buggers in the sky.... LOL...

[spokeshave]

Well that’s good news...0bambis Acorn census workers won’t get a good fix on my front door.

[Habibi]

“Anyway, a back up system using cell phone towers is already in the works.”

Uh, what?! I guess you’re kidding, aren’t you? If you aren’t, what if you’re not using a cellphone? What if you’re flying a plane, or driving a boat? Not a lot of cell towers available for that sort of environment. Having said that, even with the expecvted degradation of the constellation, it’s still in better shape than it was 25 years ago. I ‘spect we’ll muddle through whatever shape the GPS system is in.

[org.whodat]

It’s not even new news, http://www.newscientist.com/article/dn11713-tv-and-cellphone-signals-may-provide-gps-backup.html

[org.whodat]

You know what is really funny, I remember reading the post here back in 2007.

[Habibi]

Thank you for posting the link to that article. It was interesting, but as you can tell, I’m still not convinced. I’ll stipulate the cell towers could be used, and assuming that other terrestrial emitters could be used, it’s obviously possible (theoretically) to come up with some sort of position calculation. What’s less apparent to me after reading the article, what level of accuracy are we talking about using a system that they are describing?

I’ll go back to my previous point since the system described does not really lend itself to marine or aeronautical applications. Flying domestically there would be bazillions of signal sources all yammering at whatever receiver the aircraft was using. You can “line of sight” way too much at 37,000 ft.. In a marine environment, one is operating where there is nothing “line of sight”. Certainly no cell towers, tv stations or vhf/uhf sources available. This goes for aircraft as well. Yes, there are fallback technologies available, but I’ve become spoiled by having a gps receiver in the bottom of my flight case (just in case). NDB, LORAN, laser ring gyros, LNAV systems, they’re just fine and I’ve used them all, but they are not even close to the accuracy of that little box in the bottom of my flight bag that never really had to be used (but it was awfully nice to know it was in there).

Out of curiousity, did the system that was described actually go beyond a theoretical discussion? Just curious, as I truly had never heard of it till you were kind enough to point it out to me. I’m obliged for that.

[diverteach]

Our military and thier weapons is so heavily dependant upon the GPS system, do you honestly think the pentagon will allow the system to fail? I don’t think so.

[ops33]

I take it from you comment that you are familiar with flying and instrument procedures. I do not believe that cell towers can give enough accuracy to design an RNAV approach with LPV minimums. Most LPV approaches have a 250’ Height above Touchdown (HAT) but there are some with a 200’ HAT.

[org.whodat]

I'm sure the military has a top secret program as a global positioning back up. And for a computer to triangulate is child's play, three positions and bang they know where they are, no problem. There are plane tracking radar stations all over the country and the world. Their positions are fixed.

[NelsTandberg]

The more I dig into this, the more confused I am. The previous administration’s budget for FY 2009 directed the migration of LORAN-C to Dep. Homeland Security from the USCG, and the implementation of an enhanced LORAN system (LORAN-E) as a replacement. A good summary can be found at:

http://www.crossrate.com/pdfs/020608.pdf

For a primer on LORAN-E capabilities, see:

http://www.loran.org/ILAArchive/eLoran%20Definition%20Document/eLoran%20Definition%20Document-1.0.pdf

Coast Guard Commandant Allen’s thoughts on shutdown of LORAN-C are here:

http://www.uscg.mil/comdt/blog/2009/04/question-from-a-school-student.asp

What this administration does probably won’t be settled until the Air Force and the Goast Guard fight over funding, and congress critters pass the FY 2010 budget.

Cmdr Feigenblatt of the Coast Guard’s e-navigation Branch is quoted as stating, “Enhanced Loran (eLoran) does not exist in the United States. There is neither the funding nor the authority to modernize Loran-C to eLoran. Significant additional government investment of hundreds of millions of dollars would be required to transform the Loran-C system into eLoran to potentially serve as a systemic Positioning, Navigation, and Timing (PNT) backup for GPS.”

http://madmariner.com/blogs/navagear/28352

I’ve seen performance data on the UK LORAN-E prototypes in evaluation. Other references claim an upgrade to the US system would cost $400,000,000. The cynic in me says nothing will happen until broadcast communications and GMD cell phone service is degraded due to poor GPS satellite performance. Or we’ll contract with the Chinese for access to their system.

[org.whodat]

The cynic in me says nothing will happen until broadcast communications and GMD cell phone service is degraded due to poor GPS satellite performance. Or we’ll contract with the Chinese for access to their system.

ROFLOL

[org.whodat]

The Lorain E stuff is really interesting.

[Habibi]

“I’m sure the military has a top secret program as a global positioning back up.”

Yes, they’re called navigators. Sorry. Couldn’t resist.

I was on a Sacramento overnight once, and the guy I was crewing with had a family friend that was going through Nav school that had supper with us (Mongolian BBQ - excellent). I asked him, “So with all this GPS stuff, what do we need you guys for?”. Of course, the other pilot was horrified that I’d asked his friend such a question, but the young fellow laughed and said, “Ya’ know, we were wondering that too.” Apparently, the contingency plan involves not having the constellation functional at some point.

[org.whodat]

LOL, I was wondering if it were not possible to have a computer program today that would navigate from the constellation positions. I know in the past it was said a small computer did not have the speed ability to compute all the variables. They may not be true today.

[SunkenCiv]

related sidebar, but it's too boring to explain how. :')

· join · view topics · view or post blog · bookmark · post new topic ·

Google news searches: exoplanet · exosolar · extrasolar ·

[bigheadfred]

A link to the NASA satellite tracking. It’s interactive. Gives you an idea of what is up there.

http://science.nasa.gov/Realtime/jtrack/3d/JTrack3D.html

[SunkenCiv]

Thanks.

Absolute GPS to better than one meter
C.O. Alley & T. Van Flandern
http://www.metaresearch.org/solar%20system/gps/absolute-gps-1meter.ASP