Sat-nav devices face big errors as solar activity rises

[Mike]

Researchers say the Sun is awakening after a period of low activity, which does not bode well for a world ever more dependent on satellite navigation.

The Sun's irregular activity can wreak havoc with the weak sat-nav signals we use.

The last time the Sun reached a peak in activity, satellite navigation was barely a consumer product.

But the Sun is on its way to another solar maximum, which could generate large and unpredictable sat-nav errors.

It is not just car sat-nav devices that make use of the satellite signals; accurate and dependable sat-nav signals have, since the last solar maximum, quietly become a necessity for modern infrastructure.

Military operations worldwide depend on them, although they use far more sophisticated equipment.

Sat-nav devices now form a key part of emergency vehicles' arsenals. They are used for high-precision surveying, docking ships and plans are even underway to incorporate them into commercial aircraft.

Closer to home, more and more trains depend on a firm location fix before their doors will open.

More.......  http://news.bbc.co.uk/1/hi/sci/tech/8494225.stm

[Mac]

Closer to home, more and more trains depend on a firm location fix before their doors will open.

[MarkS]

Closer to home, more and more trains depend on a firm location fix before their doors will open.

I can predict the excuses already: "Sorry the trains are delayed because of the wrong kind of sun"

[Rick]

I can predict the excuses already: "Sorry the trains are delayed because of the wrong kind of sun"

...or they'll say the GPS sent them down the wrong track...

That said, I've had a GPSr since 2001, and the last Solar Maximum didn't cause it any noticable problems...

[Mac]

Closer to home, more and more trains depend on a firm location fix before their doors will open.

They use fixed induction loops at the end of the platforms and onboard detectors. Not GPS.

Heres a thought.

If the GPS signal is out by say 3m, which most of the time it is, the train, sitting at a station could think it is on the other track, as thats what the GPS is telling it.
If it thinks its on the other track, it will allow the other doors to open, allowing passengers to exit on to the track.

Dont think so.

It would not be passed as safe by HMRI.

Mac.

[Rick]

If the GPS signal is out by say 3m, which most of the time it is, the train, sitting at a station could think it is on the other track, as thats what the GPS is telling it.

...and even on a good day un-corrected civilian-grade GPS positions don't usually get that accurate. Throw in WAAS or some equivalent, and you might get accuraccy closer to a metre. Use a local differential system and you will get rather more accuracy, but as the two (or more) stations used in the differential positioning need to be fairly close they'd be taking out the suggested solar-induced inaccuracies along with the designed jitter.

Seems to me the journalist who wrote that story wasn't entirely clear about the facts... 

[MarkS]

Seems to me the journalist who wrote that story wasn't entirely clear about the facts... 

In the world of journalism, all positioning systems use satellite - even on the Underground:
http://forum.orpington-astronomy.org.uk/index.php?topic=5473.0

[mickw]

I was having a beer with a bloke in Denver a few years ago.
His company was demonstrating GPS surveying of a 1/2 mile square plot of land.  From what I understood they walked around with a GPS on a stick, took readings and the software created a 3D image of the land.

Loads of businesses have been erected on the site, so I presume it worked 

[doug]

     AAAAhhhhhhhhhh......... but does this solar activity mean that will have more lorries going down narrow lanes and blocking them up; more old ladies trying to drive in river beds and up mountain tracks, I ask myself???  

    "Well, the satnav said I was going in the right direction .......  

    Doug  

[Rick]

Loads of businesses have been erected on the site, so I presume it worked 

In the US they have a nice visible WAAS bird feeding them corrections, so a single GPSr can get accuracies nearer three or four feet, but if they were doing serious surveying then they'll be using differential positioning, with a fixed base station GPSr on a known survey mark. It records the jitter, and the positions from the roaming GPSrs can then be corrected. That'll get the positions down to military accuracy over a small area, and the military allegedly use their GPSrs to map minefields...

...but I bet, when they actually started laying foundation plans they used tapes and theodolites.

[Mac]

From what I understood they walked around with a GPS on a stick

You are correct,
however they dont rely on just the GPS satellites as they are too inaccurate!

They have a network of ground based transmitters as well at known locations, which increase the accuracy.
http://www.ordnancesurvey.co.uk/oswebsite/gps/commercialservices/index.html

Mac.

[mickw]

You are correct,

I was right ? 
Now I'm scared................

[Rick]

Now I'm scared................

Have another beer!