Yet Another Cycling Forum

General Category => The Knowledge => GPS => Topic started by: rogerzilla on 12 October, 2009, 09:11:34 pm

Title: Has anyone taken their GPS to Greenwich?
Post by: rogerzilla on 12 October, 2009, 09:11:34 pm
Mine was claiming 13ft accuracy but was at least 25 feet off the prime meridian.   ::-)
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: Chris S on 12 October, 2009, 09:14:20 pm
Mine was claiming 13ft accuracy but was at least 25 feet off the prime meridian.   ::-)

Get a life!  ;D

 ;)
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: Jurek on 12 October, 2009, 09:22:14 pm
Mine was claiming 13ft accuracy but was at least 25 feet off the prime meridian.   ::-)

I pass very close to the meridian at least twice daily, during which time I suffer dizzy spells.

Is this anything to do with you?  :D
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: rogerzilla on 12 October, 2009, 09:27:33 pm
There's an urban legend that one type of car satnav - may have been Garmin - had a software bug which only manifested itself when moving from the E to the W hemisphere, and vice-versa.  This wasn't picked up in extensive product testing, but when it got to the market almost everyone in London who bought one sent it back  ;D
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: Charlotte on 12 October, 2009, 09:30:04 pm
If you cross the meridian E-W very slowly, turn your Garmin off, cross back, turn it on and then cross E-W again, this time very fast, it displays a nekkie picture of Paris Hilton.

100% TRUFAX.
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: Chris S on 12 October, 2009, 09:36:50 pm
If you cross the meridian E-W very slowly, turn your Garmin off, cross back, turn it on and then cross E-W again, this time very fast, it displays a nekkie picture of Paris Hilton.

Wow - thanks for the warning! Yewww....
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: rogerzilla on 12 October, 2009, 09:37:47 pm
If you cross the meridian E-W very slowly, turn your Garmin off, cross back, turn it on and then cross E-W again, this time very fast, it displays a nekkie picture of Paris Hilton.

100% TRUFAX.

/makes mental note to try this on the A14 next week
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: Jurek on 12 October, 2009, 09:47:35 pm
If you cross the meridian E-W very slowly, turn your Garmin off, cross back, turn it on and then cross E-W again, this time very fast, it displays a nekkie picture of Paris Hilton.

100% TRUFAX.

*Goes out Meridian cruisin'  in search of another wit Garmin*  :o
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: simonp on 12 October, 2009, 10:21:53 pm
If you cross the meridian E-W very slowly, turn your Garmin off, cross back, turn it on and then cross E-W again, this time very fast, it displays a nekkie picture of Paris Hilton.

100% TRUFAX.

LIES!

It was Hummers!
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: Greenbank on 12 October, 2009, 10:34:24 pm
That's W-E crossing.

Ewwww.
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: ScumOfTheRoad on 12 October, 2009, 10:41:13 pm
More urban legends - the F14 fighter has a fly-by-wire navigation system. an early flgith model flipped upside down when it passed the equator. Utter twaddle I'm afraid - but a good story!
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: Craig on 16 October, 2009, 06:49:01 pm
Mine was claiming 13ft accuracy but was at least 25 feet off the prime meridian.   ::-)
Are you using the correct datum? The Greenwich Meridian is about 100m different in longitude from WGS84, which most GPS devices use as standard.
Wikipedia has more details, including a photo of a GPS above the Meridian showing it doesn't read zero: Prime Meridian - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Prime_Meridian)
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: rogerzilla on 17 October, 2009, 02:07:31 pm
Ah.  I set mine to the OS datum, which apparently is 6m to the west.  That would explain it.
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: Bledlow on 22 October, 2009, 01:55:14 pm
More urban legends - the F14 fighter has a fly-by-wire navigation system. an early flgith model flipped upside down when it passed the equator. Utter twaddle I'm afraid - but a good story!

But the F-22 navigation system failing when it flew across 180W is true. A flight of F-22s heading west to Okinawa in 2007 all suffered the same problem, had to rely on their supporting tankers for navigation. They turned back to Hawaii. The bug was fixed quickly, & they tried again - successfully.
Title: Re: Has anyone taken their GPS to Greenwich?
Post by: thing1 on 29 October, 2009, 06:02:28 pm
Mine was claiming 13ft accuracy but was at least 25 feet off the prime meridian.   ::-)
Are you using the correct datum? The Greenwich Meridian is about 100m different in longitude from WGS84, which most GPS devices use as standard.
Wikipedia has more details, including a photo of a GPS above the Meridian showing it doesn't read zero: Prime Meridian - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Prime_Meridian)

This is as a popular (http://www.gearthhacks.com/forums/archive/index.php/t-753.html) question (http://bbs.keyhole.com/ubb/ubbthreads.php?ubb=showthreaded&Number=39602) regarding (http://bbs.keyhole.com/ubb/ubbthreads.php?ubb=showthreaded&Number=30500&site_id=1#import) Google Earth too. "Even" el reg was caught out (http://www.theregister.co.uk/2006/02/06/greenwich_meridian/) by this.