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Why your GPS is off!

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(@nate-the-surveyor)
Posts: 10522
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The Prime Meridian in England is wrong

Maybe we should send this to our friend, Kent Mc. This explains his difficulty, with GPS!

I had a feeling something was off. Now I have evidence!

 
Posted : 15/08/2015 11:18 am
(@partychief3)
Posts: 87
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Still well within GIS tolerence.

But then GIS is only concerned about such important facts as; What color is it? Does it have acne? Did it vote Republican in 1980? :snarky:

 
Posted : 15/08/2015 12:53 pm
(@skwyd)
Posts: 599
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partychief3, post: 332014, member: 9053 wrote: Still well within GIS tolerence.

But then GIS is only concerned about such important facts as; What color is it? Does it have acne? Did it vote Republican in 1980? :snarky:

You forgot about "what is the APN, is it owned by the City or County, and how far from the nearest supermarket it the parcel?"

 
Posted : 17/08/2015 8:39 am
(@geonerd)
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Basically, the location of the prime meridian at Greenwich Observatory is wrong.
Excuse me! I think the prime meridian was defined by the location of the observatory - it cannot be wrong. It's like saying an original called for monument as being wrong. What is wrong is the calculation for 0 longitude for the ECEF reference frame.

 
Posted : 17/08/2015 10:00 am
(@dan-patterson)
Posts: 1272
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geonerd, post: 332220, member: 8268 wrote: Basically, the location of the prime meridian at Greenwich Observatory is wrong.
Excuse me! I think the prime meridian was defined by the location of the observatory - it cannot be wrong. It's like saying an original called for monument as being wrong. What is wrong is the calculation for 0 longitude for the ECEF reference frame.

Absolutely right!

 
Posted : 17/08/2015 10:09 am
(@geeoddmike)
Posts: 1556
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For a more sober explanation see:

http://www.rmg.co.uk/explore/astronomy-and-time/astronomy-facts/history/the-longitude-of-greenwich

Last visited the Observatory in 2005. Some photos, including my Garmin on the line, here: https://picasaweb.google.com/106803290884381691323/GeodesyRelated#5237444552549892626

The basis for the spate of articles in general interest sites is the scientific one here: http://link.springer.com/article/10.1007/s00190-015-0844-y

"Why the Greenwich Meridian moved"

 
Posted : 17/08/2015 10:36 am
(@ashton)
Posts: 562
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geonerd, post: 332220, member: 8268 wrote: Basically, the location of the prime meridian at Greenwich Observatory is wrong.
Excuse me! I think the prime meridian was defined by the location of the observatory - it cannot be wrong. It's like saying an original called for monument as being wrong. What is wrong is the calculation for 0 longitude for the ECEF reference frame.

An original called-for monument can be wrong, if it was changed by a valid boundary line agreement. The international organizations that set up the International Terrestrial Reference Frame and friends have at least as much weight as the International Meridian Conference that established the Airy Transit as the prime meridian.

 
Posted : 18/08/2015 5:27 am