Author Topic: Will GPS be affected by the earthquake  (Read 2094 times)

Will GPS be affected by the earthquake
« on: March 14, 2011, 04:09:23 pm »
So Japan itself has shifted by 4m, the world moved on it's axis by cm and changed rotation period by 1.8 silly milliseconds or somesuch.

Will this affect the timing/clock functions in GPS signals?
<i>Marmite slave</i>

Re: Will GPS be affected by the earthquake
« Reply #1 on: March 14, 2011, 04:12:08 pm »
No, the necessary adjustments will be in the ephemeris almanac (which is transmitted along with the GPS signal and is only valid for a couple of hours anyway) to take most of the shifting into account.

Every GPS receiver has to handle the ephemeris data otherwise it would be woefully inaccurate within a matter of days.

Individual positions in Japan may be 4m out if just one section of the country (or continent) has shifted but that can be seen as a fault in the underlying mapping as the GPS receiver will be correctly identifying its position relative to the satellites, but the ground underneath has changed...
"Yes please" said Squirrel "biscuits are our favourite things."

frankly frankie

  • I kid you not
    • Fuchsiaphile
Re: Will GPS be affected by the earthquake
« Reply #2 on: March 14, 2011, 04:14:50 pm »
It doesn't seem to have caused a problem in previous incidents.

The Chilean earthquake shortened a day by 1260ns.  The Sumatran quake of 2004 shortened the day length by about 6800ns.

There's a lot of error-correction feeding back into the GPS system all the time.
It's not dark yet but it's getting there.

andygates

  • Peroxide Viking
Re: Will GPS be affected by the earthquake
« Reply #3 on: March 14, 2011, 04:23:07 pm »
So we're not going to have to run a bot to move every OSM node?  Phew :)
It takes blood and guts to be this cool but I'm still just a cliché.
OpenStreetMap UK & IRL Streetmap & Topo: ravenfamily.org/andyg/maps updates weekly.

frankly frankie

  • I kid you not
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Re: Will GPS be affected by the earthquake
« Reply #4 on: March 14, 2011, 04:45:28 pm »
West and East of a line down the Pacific, in opposite directions?
Well, nobody said the Earth was unaffected ...

The GPS corrections are quite substantial in their effect - taking the Chilean quake as an example, if left uncorrected it would have introduced a positional error of around 375 metres per day.
It's not dark yet but it's getting there.

Re: Will GPS be affected by the earthquake
« Reply #5 on: March 14, 2011, 04:53:43 pm »
I love that they built the atomic clocks in those satellites to run slow - because of relativistic effects.

It makes you realise how silly science deniers are, IMO. Was Einstein right? If not, your satnav would have you driving in the sea by now ;)

Re: Will GPS be affected by the earthquake
« Reply #6 on: March 15, 2011, 11:42:40 pm »
...

The Chilean earthquake shortened a day by 1260ns.  The Sumatran quake of 2004 shortened the day length by about 6800ns.

...


No wonder I'm feeling tired.

andygates

  • Peroxide Viking
Re: Will GPS be affected by the earthquake
« Reply #7 on: March 15, 2011, 11:51:00 pm »
It makes you realise how silly science deniers are, IMO. Was Einstein right? If not, your satnav would have you driving in the sea by now ;)
Those sort of people drive into the sea anyway and then blame the satnav.  ;)

I suppose, once all the drama has subsided a bit, some Japanese map geeks should go out and get reference traces from high-accuracy GPS, to see if the whole map database needs a shift. 
It takes blood and guts to be this cool but I'm still just a cliché.
OpenStreetMap UK & IRL Streetmap & Topo: ravenfamily.org/andyg/maps updates weekly.

Re: Will GPS be affected by the earthquake
« Reply #8 on: March 16, 2011, 06:52:08 pm »
There have been various numbers floating around for the eastward shift of Honshu, from 2.4 to 4 metres.
"A woman on a bicycle has all the world before her where to choose; she can go where she will, no man hindering." The Type-Writer Girl, 1897

Alouicious

Re: Will GPS be affected by the earthquake
« Reply #9 on: March 23, 2011, 09:38:23 am »
The only thing you have to worry about is a Crustal Displacement.

This is where the entire crust shifts round by any distance it chooses. An inbalance of ice sheet on either pole wil cause this to happen.

When it happens, pray it moves the UK closer to the rotational equator.  ;D

If its a quick shift, anyone in the building trade will have a 'job for life'; and folks who live above 350ft elevation will stay dry.  ;D Cheerio London, Manchester, Liverpool, Southampton, Edinburgh, Glasgow; Hello Birmingham, new capital of Great Britain


Re: Will GPS be affected by the earthquake
« Reply #10 on: March 23, 2011, 10:25:26 am »
earthquakes no, but this will if you live in that area
Quote
The UK Ministry of Defence has informed Ofcom of the following GPS jamming exercise:

Dates: Jamming will be conducted on a maximum of 3 week-days in the period 10-21 July 2011. Times: 0900 -1730 BST.

Location: Jamming aircraft will orbit at 10,000ft above mean sea-level (AMSL) along a 50nm flightpath on a heading of 270°T from Kirkwall, starting 10nm to the west of Kirkwall and ending 60nm to the west of Kirkwall

Possible areas affected: The GPS jamming is likely to affect civilian Standard Positioning Service (SPS) receivers over a large area. A minimum jammer to signal vulnerability of 30dB has been assumed for a civilian receiver. Signal theory suggests that a SPS civilian receiver should have approximately 32dB of jamming resistance.

Safety of Life Operations: Safety of life operations will take precedence over exercise activities at all times. To this end, the AWC is open to further discussion with any official recipient on the potential implications of this jamming exercise.

Contact point: During the exercise, any official recipient (or their delegated representative) and any member of the Emergency Services may terminate the jamming for safety reasons by calling the contact numbers below:

(1) Primary: Duty Controller Flying (TLT), RAF Kinloss - Tel: 01309 617857.
(2) Backup: Duty Controller Flying (TLT), RAF Lossiemouth - Tel: 01343 817428.
(3) Tertiary: Duty Air Surveillance Officer, National Air and Space Operations Centre Tel: 01494 494812.

Note: Safety of life operations will take precedence over exercise activities at all times.


Jaded

  • The Codfather
  • Formerly known as Jaded
Re: Will GPS be affected by the earthquake
« Reply #11 on: March 23, 2011, 10:33:03 am »
Might be worth putting a new thread up with that, numbnuts?
If you don't like your democracy, vote against it.

DaveJ

  • Happy days
Re: Will GPS be affected by the earthquake
« Reply #12 on: March 23, 2011, 02:53:11 pm »
Might be worth putting a new thread up with that, numbnuts?

Not a lot of cycle routes 10km west of Kirkwall  ;)

Dave

GrahamG

  • Babies bugger bicycling
Re: Will GPS be affected by the earthquake
« Reply #13 on: March 24, 2011, 12:47:52 pm »
Hello Birmingham, new capital of Great Britain


*shudders*
Brummie in exile (may it forever be so)