# Meridians and parallels signed on roads



## ChrisZwolle (May 7, 2006)

Yes, that sign is technically not correct or not exactly on 45 N.


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## g.spinoza (Jul 21, 2010)

They rounded up. Unacceptable, in a town so close to the Institute of Metrology


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## Penn's Woods (Apr 8, 2010)

I believe there's a 45th parallel sign just south of the U.S./Canadian border on I-87 - the New York/Montreal highway. The border itself is supposed to be on the 45th parallel in that area (between the St. Lawrence and Connecticut rivers) but when they surveyed it in the early 19th century they didn't get it quite right. And I imagine no one wants to redo it because it would affect property lines and such.


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## Penn's Woods (Apr 8, 2010)

g.spinoza said:


> They rounded up. Unacceptable, in a town so close to the Institute of Metrology


Or did they round one up and the other down?
Really, precision's important! ;-)


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## Verso (Jun 5, 2006)

It's just to look better probably.


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## MattiG (Feb 11, 2011)

ChrisZwolle said:


> Nope
> 
> _It is the line that marks the theoretical halfway point between the equator and the South Pole. (The true halfway point is 16.2 kilometres (10.1 mi) south of this parallel because the Earth is not a perfect sphere but bulges at the equator and is flattened at the poles.)_


In fact, it is not a theoretical halfway. In the geodesy, the Earth is pretty accurately modeled by an ellipsoid, instead of a sphere. The latitudes usually are geodetic ones (called geographic, too, see picture below). On the surface of an ellipsoid, the 45 degrees latitude is NOT at the halfway of the equator and poles. The more the flattening of the ellipsoid is the more close to the equator the 45 degrees latitude lies.










In the ellipsoid of the WGS84 datum (used by GPS), the equator-to-pole distance is 10001.966 kilometres. The distance from the equator to the latitude 45 degrees is 4984.944 kilometers, and the remaining distance to the pole is 5017.021 kilometres.


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## italystf (Aug 2, 2011)

Verso said:


> Any road sign for the Antarctic Circle?


Not a *road* sign obviously, but a sign anyway. :nuts:


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## italystf (Aug 2, 2011)

Equator in Kenya

























Equator in Uganda









Equator in Equador


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## italystf (Aug 2, 2011)

It's possible that when parallels were estabilished they though that 45° was exactly halfway between the Equator and the Pole and only later, with more accurate instruments, they discovered it wasn't exactly like that?
To make other examples, when the meter was estabilished as lenght unit in the XVIII century, it was defined as 1/20,000,000 of a meridian, but now we know that a meridian isn't exactly 20,000km long but a bit more.
Or when the Gregorian calendar was estabilished in the Middle Age, they set the year 0 few years after (some say 7) the date that historians think it's more likely Jesus was born.
However, after some centuries, those mistakes become accepted facts.


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## Penn's Woods (Apr 8, 2010)

^^Or fixing them is more inconvenient than it's worth.


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## MattiG (Feb 11, 2011)

italystf said:


> It's possible that when parallels were estabilished they though that 45° was exactly halfway between the Equator and the Pole and only later, with more accurate instruments, they discovered it wasn't exactly like that?
> To make other examples, when the meter was estabilished as lenght unit in the XVIII century, it was defined as 1/20,000,000 of a meridian, but now we know that a meridian isn't exactly 20,000km long but a bit more.
> Or when the Gregorian calendar was estabilished in the Middle Age, they set the year 0 few years after (some say 7) the date that historians think it's more likely Jesus was born.
> However, after some centuries, those mistakes become accepted facts.


The flattened shape of the Earth was known earlier than the meter was invented, as well as using the ellipsoid as the most accurate simple approximation of the shape of the earth. Of course, the figures have turned more accurate as the measurement technology has improved.

It is a misconception that the 45 degree latitude lies exactly at the halfway between the equator and the poles. That assumption is valid only for spheres, not ellipsoids. It is easy to end up this misconception, because the Earth looks like a sphere: the flattening is small, about 0.34 per cent only.

The distance from the equator to the poles is pretty close to 10000 kilometers, reflecting the fact that 18th century surveyors were skilled enough the take the Earth's oblateness into account.


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## CNGL (Jun 10, 2010)

I've realized a mistake in my statement about 45º, I'll correct it.


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## Verso (Jun 5, 2006)

italystf said:


> Not a *road* sign obviously, but a sign anyway. :nuts:


I wonder why they placed it exactly here.


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## italystf (Aug 2, 2011)

Verso said:


> I wonder why they placed it exactly here.


It could be along the path between two research stations, I don't know. In Antarctica there are paths (travelled with snowmobiles and ATVs) all the way from the coast to the geographic South Pole (McMurdo station).
In that pic you can see the track left by some vehicle in the background.


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## Kanadzie (Jan 3, 2014)

Penn's Woods said:


> I believe there's a 45th parallel sign just south of the U.S./Canadian border on I-87 - the New York/Montreal highway. The border itself is supposed to be on the 45th parallel in that area (between the St. Lawrence and Connecticut rivers) but when they surveyed it in the early 19th century they didn't get it quite right. And I imagine no one wants to redo it because it would affect property lines and such.


I don't remember one on 87 but I do remember one. Maybe I-89 or I-91?


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## Verso (Jun 5, 2006)

italystf said:


> It could be along the path between two research stations, I don't know. In Antarctica there are paths (travelled with snowmobiles and ATVs) all the way from the coast to the geographic South Pole (McMurdo station).
> In that pic you can see the track left by some vehicle in the background.


Yeah, but the South Pole Traverse doesn't cross the Antarctic Circle.


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## Penn's Woods (Apr 8, 2010)

Kanadzie said:


> I don't remember one on 87 but I do remember one. Maybe I-89 or I-91?


Haven't been on either of them in a while. Maybe in Maine?


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## Kanadzie (Jan 3, 2014)

maybe, but if you remember more on 87 I'll defer, I rarely go all the way to Canada by 87, only a couple times


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## Penn's Woods (Apr 8, 2010)

^^Nah, don't trust my memory on this one....


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## Verso (Jun 5, 2006)

This is in the Australian-claimed part of Antarctica.


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