Warning. Adjust your gps as thay are all out......

[roblpm]

Just stood on the Meridian line at Greenwich and my GPS showed 5 seconds West. Zero was about 100 metres away.

So we are obviously all not where we think we are......?!

 

[sarabande]

Sneaky blighters these European Geocrats.

Fear not. Corbyn will add the relocation of the Greenwich Meridian to his list of other tasks after he wins. A task which can be given with confidence to Ms Abbott.

 

[roblpm]

Sneaky blighters these European Geocrats.

Fear not. Corbyn will add the relocation of the Greenwich Meridian to his list of other tasks after he wins. A task which can be given with confidence to Ms Abbott.

Im not sure it is a natural Corbyn policy. More ukip / tory territory. Have our own datum to line up with Greenwich?

 

[Aeolus]

Next week Trump plans to withdraw the USA from the agreements reached at the International Meridian Conference of 1884 as these were a bad deal for America. With immediate effect the global GPS system will be recalibrated to show zero longitude passing through Trump Tower in New York.

You have been warned!!

 

[roblpm]

Actually semi seriously.... How come the zero isn't at the observatory?!

 

[Dipper]

After Brexit we will be in the Atlantic on the other side of Ireland and the Channel Tunnel will go to Dublin. Solves that border issue.

 

[macd]

Actually semi seriously.... How come the zero isn't at the observatory?!

They got it wrong back in the day, due to factors such as the Earth's flattening towards the poles to a degree they couldn't calculate. They movement east actually came in stages, many of them at the behest of the Observatory itself as better instruments became available. It's now calculated to be just over 100m out (which should please the OP).

 

[Orion Jim]

Next week Trump plans to withdraw the USA from the agreements reached at the International Meridian Conference of 1884 as these were a bad deal for America. With immediate effect the global GPS system will be recalibrated to show zero longitude passing through Trump Tower in New York.

You have been warned!!

Tedious.....

 

[roblpm]

They got it wrong back in the day, due to factors such as the Earth's flattening towards the poles to a degree they couldn't calculate. They movement east actually came in stages, many of them at the behest of the Observatory itself as better instruments became available. It's now calculated to be just over 100m out (which should please the OP).

But how could they get it wrong? Isn't it am arbitrary point?

 

[Robin]

Next week Trump plans to withdraw the USA from the agreements reached at the International Meridian Conference of 1884 as these were a bad deal for America. With immediate effect the global GPS system will be recalibrated to show zero longitude passing through Trump Tower in New York.



You have been warned!!

:biggrin-new::biggrin-new::biggrin-new:

 

[macd]

But how could they get it wrong? Isn't it am arbitrary point?

It certainly began that way. Then they discovered that the earth wasn't quite the homogeneous sphere they'd imagined it to be, so the axes the resulting meridians implied didn't actually cross where they should (and certainly not at the same place). This is more than just scientific vanity: getting the properties of the 'globe' wrong, apart from being an undesirable thing in itself, could ultimately lead to less accurate navigation in other parts of the world. It also had important implications for astronomy.

As mentioned, the early adjustments were entirely at the discretion of the Observatory itself (because its role was to be, above all else, accurate), so subsequent ones can scarcely be blamed on Johnny Foreigner. It was probably inevitable (if unknown) that, wherever the prime meridian was first established, it would have to move; so, by being the first, this was always the fate of Greenwich.

Clearly they could have contrived to keep 0 degrees exactly where they'd first plonked it on Greenwich Hill, but the meridian that passed through it would have had to describe a different path everywhere else. You can probably envisage that where the prime meridian meets the equator (which is not arbitrary) is geometrically far more important than where it happens to brush it in some random higher latitude. But in defining one, Greenwich had also defined the other -- and both, it turned out, could not be correct. Anyway, evidently more scientists wanted to play Galileo than pope.

P.S. Out of interest, roblpm, which datum was your GPS set to? Did you try more than one?

 

[Lon nan Gruagach]

It certainly began that way. Then they discovered that the earth wasn't quite the homogeneous sphere they'd imagined it to be, so the axes the resulting meridians implied didn't actually cross where they should (and certainly not at the same place). This is more than just scientific vanity: getting the properties of the 'globe' wrong, apart from being an undesirable thing in itself, could ultimately lead to less accurate navigation in other parts of the world. It also had important implications for astronomy.

As mentioned, the early adjustments were entirely at the discretion of the Observatory itself (because its role was to be, above all else, accurate), so subsequent ones can scarcely be blamed on Johnny Foreigner. It was probably inevitable (if unknown) that, wherever the prime meridian was first established, it would have to move; so, by being the first, this was always the fate of Greenwich.

Clearly they could have contrived to keep 0 degrees exactly where they'd first plonked it on Greenwich Hill, but the meridian that passed through it would have had to describe a different path everywhere else. Evidently more scientists wanted to play Galileo than pope.

P.S. Out of interest, roblpm, which datum was your GPS set to? Did you try more than one?

Nope, still dont "get it", is there a good online info about htis, or is it start with good (sic) ol Wiki?

 

[Sandy]

Next week Trump plans to withdraw the USA from the agreements reached at the International Meridian Conference of 1884 as these were a bad deal for America. With immediate effect the global GPS system will be recalibrated to show zero longitude passing through Trump Tower in New York.

I am sure you are aware that the Russians measure from Moscow and the French from Paris.

 

[macd]

Nope, still dont "get it", is there a good online info about htis, or is it start with good (sic) ol Wiki?

Reasonable enough, Dougal, which is why I added a bit, unfortunately just after you posted. Memories from uni nearly 50 years ago don't always leap forward with alacrity.

I imagine that the good online info is probably too complicated for anyone who has to ask someone else to find it
(Cheap shot, especially at you, but I couldn't resist.)

 

[PuffTheMagicDragon]

The only reason why it passes through Greenwich is that the French wanted it to pass through Paris. This, quite understandably, led to the old GMT because, let's face it, who would want to have PMT as a standard?

 

[knuterikt]

Nope, still dont "get it", is there a good online info about htis, or is it start with good (sic) ol Wiki?

Try this https://en.m.wikipedia.org/wiki/IERS_Reference_Meridian

 

[roblpm]

It certainly began that way. Then they discovered that the earth wasn't quite the homogeneous sphere they'd imagined it to be, so the axes the resulting meridians implied didn't actually cross where they should (and certainly not at the same place). This is more than just scientific vanity: getting the properties of the 'globe' wrong, apart from being an undesirable thing in itself, could ultimately lead to less accurate navigation in other parts of the world. It also had important implications for astronomy.

As mentioned, the early adjustments were entirely at the discretion of the Observatory itself (because its role was to be, above all else, accurate), so subsequent ones can scarcely be blamed on Johnny Foreigner. It was probably inevitable (if unknown) that, wherever the prime meridian was first established, it would have to move; so, by being the first, this was always the fate of Greenwich.

Clearly they could have contrived to keep 0 degrees exactly where they'd first plonked it on Greenwich Hill, but the meridian that passed through it would have had to describe a different path everywhere else. You can probably envisage that where the prime meridian meets the equator (which is not arbitrary) is geometrically far more important than where it happens to brush it in some random higher latitude. But in defining one, Greenwich had also defined the other -- and both, it turned out, could not be correct. Anyway, evidently more scientists wanted to play Galileo than pope.

P.S. Out of interest, roblpm, which datum was your GPS set to? Did you try more than one?

Wgs 84. Didn't try a different one. It seems to agree with what it says on the Wikipedia page. 100 metres out.

 

[roblpm]

Excellent. And it moves 2.5 cm a year cos the plate we are on moves! Its a wonder anyone knows where they are!

 

[Daydream believer]

Next week Trump plans to withdraw the USA from the agreements reached at the International Meridian Conference of 1884 as these were a bad deal for America. With immediate effect the global GPS system will be recalibrated to show zero longitude passing through Trump Tower in New York.

You have been warned!!

Which means that when he does finally go to nuke Kim Jong-un he will probably miss & obliterate the other half of Japan that they missed last time
That is assuming his aircraft carriers have actually found N Korea & are not still circumnavigating Australia on a so called "naval exercise"