GPS Backup system being mothballed

[Modelworks]

I really think it unfair that the USA pays for GPS and everyone else uses it.

 

[Modelworks]

Most navigational military equipment does not rely solely on GPS to function. Still that's pretty concerning. What happened with the European program - I think it was called Galileo?

I was surprised when I was on a Navy ship and a officer was using a sextant even though they had all the latest gear. I was told it is a requirement that officers who do navigation know how to navigate without navigational aids like GPS.

 

[dainthomas]

I was surprised when I was on a Navy ship and a officer was using a sextant even though they had all the latest gear. I was told it is a requirement that officers who do navigation know how to navigate without navigational aids like GPS.

When I was at sea the quartermasters were always verifying the position by sextant. It would be pretty lame to have your entire fleet disabled if an enemy or a CME destroyed all the satellites.

 

[CallMeJoe]

(Selective Availability) And the collective sound of every minivan/SUV in the US simultaneously running into trees and telephone poles would be truly deafening!

The beauty of the system is that the Navy could put in huge errors in one area (North Korea? Iran?) that would affect that area and its neighbors while leaving the accuracy in the US undisturbed. There is also an encrypted GPS signal (available only to military grade GPS receivers) unaffected by the selective availability inflicted on plain vanilla GPS receivers; our aircraft and artillery could use accurate GPS targeting while our enemies are entirely befuddled.

 

[GroundedSailor]

Actually most ships probably have a LORAN receiver.

No, most old ships have Loran-C.

Loran use went out in the mid 90's when Satnav & then GPS became common. Loran / Decca / Omega have been dying since then.

These days, even ships fitted with Loran rarely, if ever, use it.

 

[GroundedSailor]

What do you mean "If"? It's called "Selective Availability" and was turned off for civilian GPS users in 2000. The US Navy (custodians of GPS) can turn it back on and set in whatever error they see fit if it suits national security needs.

Absolutely correct. Even though the turned off the deliberate random error called Selective Availibility, the US Navy maintains the ability to distort the position information and special receivers are needed to decode the inaccuracies. These are only with the US Navy.

If selective ability was switched on, most car GPS units would be inaccurate enough to be useless for driving around.

 

[BeauJangles]

I really think it unfair that the USA pays for GPS and everyone else uses it.

But by paying for it, we also maintain control of its usage and, with that, maintain an enormous amount of power. I wouldn't be surprised to see China launch a rival system in the next 20 years, mostly out of national security concerns.

 

[Patranus]

Obummer

Solar flares set to wreak havoc on GPS signals
The sun's activity isn't usually a hot topic around these parts, but when it threatens to derail satellite navigation services around the world, it must surely take center stage. UK researchers have corroborated Cornell's 2006 warning that our solar system's main life-giver is about to wake up and head toward a new solar maximum -- a period of elevated surface activity and radiation. It is precisely that radiation, which can be perceived in the form of solar flares, that worries people with respect to GPS signaling, as its effects on the Earth's ionosphere are likely to cause delays in data transmission from satellites to receivers and thereby result in triangulation errors. Still, it's more likely to be "troublesome than dangerous," but inaccuracies of around 10 meters and signal blackouts that could last for hours are being forecast in the absence of any intervening steps being taken. So yes, you now have another reason not to trust your GPS too much.

http://www.engadget.com/2010/02/10/solar-flares-set-to-wreak-havoc-with-gps-signals/

 

[frostedflakes]

FWIW, solar flares also wreak havoc on terrestrial RF broadcasts, including LORAN. Solar phenomena in general are just bad all around for our communications systems.

 

[CallMeJoe]

Obummer

http://www.engadget.com/2010/02/10/solar-flares-set-to-wreak-havoc-with-gps-signals/

An excellent argument for maintaining a navigation system far more subject to atmospheric interference and RFI than GPS.

 

[Patranus]

An excellent argument for maintaining a navigation system far more subject to atmospheric interference and RFI than GPS.

You might want to read up on the ionosphere and the types of radiation produced by solar flares.

LORAN is relatively immune to interstellar radiation when compared GPS.

 

[Fox5]

What do you mean "If"? It's called "Selective Availability" and was turned off for civilian GPS users in 2000. The US Navy (custodians of GPS) can turn it back on and set in whatever error they see fit if it suits national security needs.

I've heard it was shut off, because processing power, even in portable gps devices, had become great enough that the error function could basically be discovered and calculated out to get something close to the real position anyway.

 

[CallMeJoe]

I've heard it was shut off, because processing power, even in portable gps devices, had become great enough that the error function could basically be discovered and calculated out to get something close to the real position anyway.

The randomized error of selective availability could be averaged out over a period of time for a stationary unit, but a moving receiver has no such ability. Detecting an intentionally programmed error from the satellites is more difficult.

 

[GroundedSailor]

You might want to read up on the ionosphere and the types of radiation produced by solar flares.

LORAN is relatively immune to interstellar radiation when compared GPS.

Relatively compared to GPS yes, but immune no. LORAN is radio navigation and radio wave propagation is affected by solar flares.

LORAN is also subject to skywave interference which is the signal reflecting off the ionosphere in normal times. Changes in the ionosphere also affect the LORAN signal.

 

[GroundedSailor]

The randomized error of selective availability could be averaged out over a period of time for a stationary unit, but a moving receiver has no such ability. Detecting an intentionally programmed error from the satellites is more difficult.

The US Navy has equipment that can correct for SA on mobile units. In any case they use the P-code not the C/A code which civilian units use.

DGPS is one method which can reduce the effect of SA which is one of the reasons why SA was turned off.

 

[Colt45]

I thought GPS had hot spares and all that jazz.

There's always GLONASS too

 

[Siddhartha]

People complain about the deficit, and then complain when budget cuts are made.

 

[JEDIYoda]

Yes, it should. Didn't Obama kill the next generation GPS? What's even more concerning is no backup for military GPS use - which I would HAVE to assume is in place. I don't pretend to know a lot about it.

You thin k the military is going to blab all over creation that they do have a back up??? duh...

 

[GroundedSailor]

You thin k the military is going to blab all over creation that they do have a back up??? duh...

It's common knowledge there are 2 in orbit spares (satellite) all the time.