definitive GPS location of the north/south pole

July 30, 2007

I guess this is more relevant to the south pole as that doesn't shift (nearly as much) as the ice sheet over the north pole. But having watched the recent Top Gear programme where two teams raced to get to the north pole and been a bit miffed when they "proved" they'd arrived, showing their GPSr displaying N78° 36' 7" W 104° 11' 8" (nowhere near the pole as far as I understand) it got me thinking about what a GPSr would actually read at the North Pole.

Longitude could be a complete mess by then as by that location all the lines would be converging into one spot - but lattitude - surely that would be pretty close to N 90 degrees?

78 degrees is quite far north - inside the arctic circle I guess, but I'd have thought complete madness for anyone to even try to claim that this is the north pole?

Am I wrong or have the Top Gear production team shown how incompetent they are at understanding GPS readings? Or is there something about "North Pole" that I don't fully understand - they never mentioned magnetic north during the programme - but were they actually racing there (to be able to say they were telling the truth and at the same time not go through the true rigors of going to the true pole)?

Anyway - the original question still stands - what would a GPS REALLY say for lattitude *at* the pole?

As an aside, I know there are a couple of caches on the Antarctic continent - I wonder which one's closest to the South Pole? <_<

Edit: I've since discovered that magnetic north is at roughly 78°35.7′N, 104°11.9′W still many hundreds of miles from where Top Gear actually claimed to be at the time...

Edited July 30, 2007 by Eclectic Penguin

1.3k · July 31, 2007

Everyone knows that Chorley is the North Pole, and everyone else is a frickin Southerner! <_<

July 31, 2007

I've since discovered that magnetic north is at roughly 78°35.7′N, 104°11.9′W still many hundreds of miles from where Top Gear actually claimed to be at the time...

Actually only about a mile. Their position was 1 minute of Latitude different to the position you give for the Magnetic pole.

The Nauticalmile is defined as a minute of Latitude and is 2020yards. (or somewhat less of those metric thingies)

It is quite useful to remember this when caching as it means that the third decimal point of minutes is 2 yards North-South and about 1.25 yards East-West (in the midlands but it varies slightly with Latitude).

July 31, 2007

I spotted that on the program too. Why isn't the North Pole a bit nearer to 90° North? I know we're talking magnetic North - but 11.5° seems a loooong way out...

July 31, 2007

Funny we saw the program (taped) last night too and when it got to the end we just looked at each other! A browse through an atlas told us they got to the location of the magnetic north pole as it was in 1995. This site http://gsc.nrcan.gc.ca/geomag/nmp/northpole_e.php gives details. Currently the magnetic north is at about 82degrees and it is moving about 40km a year. What I hadn't appreciated is that the pole wonders about 80km on a daily basis too due to interaction of charged particles from the sun with the magnetic field.

As to the location of true north as shown by a GPS it would be nice if it was 90d 00.000'N, arbitrary E/W but something tells me it isn't that simple. The datum will probably mess things up considerably plus you might only get low angle satellite coverage.

1.3k · July 31, 2007

Just lots of ice: -

http://tinyurl.com/2vyoyb

Jon

2.2k · July 31, 2007

Everyone knows that Chorley is the North Pole, and everyone else is a frickin Southerner!

Think I prefer Wizzard/Book of Shadows popcorn

July 31, 2007

The Magnetic North Pole can be quite some distance from the True North Pole as its exact position varies, hence the gradual change of magnetic variation in any one place and the fact that magnetic variation is different wherever one is on earth.

July 31, 2007

I've since discovered that magnetic north is at roughly 78°35.7′N, 104°11.9′W still many hundreds of miles from where Top Gear actually claimed to be at the time...

Actually only about a mile. Their position was 1 minute of Latitude different to the position you give for the Magnetic pole.

The Nauticalmile is defined as a minute of Latitude and is 2020yards. (or somewhat less of those metric thingies)

It is quite useful to remember this when caching as it means that the third decimal point of minutes is 2 yards North-South and about 1.25 yards East-West (in the midlands but it varies slightly with Latitude).

Sorry - you're quite right. I cut and pasted the wrong figures - the one I meant to use was 82.7° N 114.4° W which is relatively accurate to what it would be today - and what Top Gear should have been aiming for on their GPSr.

It seems that they were aiming for the magnetic north pole (without telling us) and got it completely wrong.

The whole point of the programme was to show that the car would survive in the extreme conditions of the *North Pole*, disproving many of the theories that the car would fail (in an environment where aviation fuel would freeze) - and they proved this by not going anywhere near there!

I've always wondered - how would the early explorers know they've gotten to the pole? Scot knew he got there because he saw Amundsen's flag already there - but how did Amundsen know he'd arrived at the pole?

3.8k · July 31, 2007

I've always wondered - how would the early explorers know they've gotten to the pole? Scot knew he got there because he saw Amundsen's flag already there - but how did Amundsen know he'd arrived at the pole?

When he stopped going downhill and started going up again <_<

July 31, 2007

Everyone knows that Chorley is the North Pole, and everyone else is a frickin Southerner!

Think I prefer Wizzard/Book of Shadows popcorn

:) :drama:

July 31, 2007

A degree of artistic freedom has been used in the programme in the name of entertainment.

They've used the position used in a competition called 'Polar Race 2007', which is the position the north pole was at 11 years ago

3.9k · July 31, 2007

I've always wondered - how would the early explorers know they've gotten to the pole? Scot knew he got there because he saw Amundsen's flag already there - but how did Amundsen know he'd arrived at the pole?

If you're at the (geographic) pole, sometime reasonably in the middle of summer (and you aren't going to go at any other time!), the sun will stay at (essentially) the same height/angle above the horizon for a whole day. There's only one sunrise and one sunset per year at the poles.

July 31, 2007

I've always wondered - how would the early explorers know they've gotten to the pole? Scot knew he got there because he saw Amundsen's flag already there - but how did Amundsen know he'd arrived at the pole?

If you're at the (geographic) pole, sometime reasonably in the middle of summer (and you aren't going to go at any other time!), the sun will stay at (essentially) the same height/angle above the horizon for a whole day. There's only one sunrise and one sunset per year at the poles.

Is this true? Even midsummer's day, I thought the elevation of the sun varied throughout the day (but never went beneath the horizon). I could be wrong on this though.

The second half I fear isn't true either. While it's true that there would be several months in the year where the sun doesn't go below the horizon and there are several months of darkness, I understand that the period between no sunlight and 24 hours a day sunlight, the sun would rise and fall over the horizon and there would be a day, twice a year (in April/October) where there would be 12 hours of light and 12 hours of darkness.

July 31, 2007

A degree of artistic freedom has been used in the programme in the name of entertainment.

They've used the position used in a competition called 'Polar Race 2007', which is the position the north pole was at 11 years ago

Yeah, I know this, as they do in all their specials. I just felt they could have gotten away with the fib if they hadn't shown a GPSr "proving" they'd arrived there with figures that weren't even close to the pole. They're always quite entertaining but also usually bend the truth a tad in the name of entertainment. Everything isn't as it seems very often in the construction projects they have on the show itself too - but it's all in the name of entertainment and I still enjoy watching Top Gear.

I was dead chuffed to be invited to be part of the audience a couple of seasons ago in the show where they converted three cars into boats - definitely the best show I've been to as a member of the audience by a long mark. Completely the opposite to Big Brother (a long time ago now) where the audience were treated merely as props and herded like cattle after queueing for many hours).

Apparently, if they actually filmed in the genuine conditions of the north pole, they'd have to use special batteries as the NiMh batteries used by conventional cameras drain in about 5-10 minutes when extremely cold. I wouldn't be too surprised if they had to take these precautions anyway.

July 31, 2007

Apparently, if they actually filmed in the genuine conditions of the north pole, they'd have to use special batteries as the NiMh batteries used by conventional cameras drain in about 5-10 minutes when extremely cold. I wouldn't be too surprised if they had to take these precautions anyway.

A while ago I was in N Finland (only 68N, so well inside the arctic circle, but nowhere near the pole) in cold conditions (-20 to -30C ... and colder) with my GPSMap 76S in an outer pocket.

The display became sluggish and died due to the cold and I assumed the whole thing had shut down but despite having no display it bravely soldiered on and recorded my track as requested for a few hours (long enough for us to get to our destination). Let's hear it for Garmin!

Can't remember precisely what batteries I was using, but probably fresh Duracell non rechargeables, because I found my rechargeables didn't last long (and I had nowhere to charge them up again).

Just to stay on topic, here's a pic of a TB that I had with me at the time.

July 31, 2007

Whatever the location used, it was still a race and they beat team dog, and showed just what the vehicles were capable of.

In one shot there were 3 vehicles, and I presume it was either filmed from a 4th or they had to go back to pick up the cameraman. The dog team was also filmed from a moving vehicle... there was plenty of back up, I'm sure.

They'll always stage things going wrong to make it more entertaining - I can't believe the bolt stuck to his lip was genuine, for example.

Very good show though, long may it continue!

I presume that at the north pole the sun stays at roughly the same elevation all day long, just going all the way around you. There will be a slight change as the sun's elevation rises to a max in mid summer, etc etc..

July 31, 2007

I've always wondered - how would the early explorers know they've gotten to the pole? Scot knew he got there because he saw Amundsen's flag already there - but how did Amundsen know he'd arrived at the pole?

If you're at the (geographic) pole, sometime reasonably in the middle of summer (and you aren't going to go at any other time!), the sun will stay at (essentially) the same height/angle above the horizon for a whole day. There's only one sunrise and one sunset per year at the poles.

Is this true? Even midsummer's day, I thought the elevation of the sun varied throughout the day (but never went beneath the horizon). I could be wrong on this though.

The second half I fear isn't true either. While it's true that there would be several months in the year where the sun doesn't go below the horizon and there are several months of darkness, I understand that the period between no sunlight and 24 hours a day sunlight, the sun would rise and fall over the horizon and there would be a day, twice a year (in April/October) where there would be 12 hours of light and 12 hours of darkness.

Hmm, having given this a bit of thought (involving a torch and football) I think I may be talking complete rubbish - both of the original statements are correct - that the sun's elevation appears constant throughout the day and that indeed there is only one true sunset/sunrise at the true poles.

Funny this, although I understand the mechanics of how the arctic circle works, this had never occurred to me before.

6.2k · July 31, 2007

How to find if you're at the geographic north pole:

At night, look up. The pole star (Polaris) should be right above you- well, 42′ off.

During the day (except December 25th) look for Santa

July 31, 2007

the only problem with that is that the night lasts 6 months and I presume most polar explorers would rather have some daylight?!

6.2k · July 31, 2007

The *only* problem with that? You're far too kind!

Seriously though, if you can't rely on a compass for magnetic North, or the stars for geographic North, it's no wonder there's still a lot of controversy about who got there first.

July 31, 2007

Out of interest I entered N90 00.000 Wxxxx in to Google Maps so see what would happen, and I broke it. http://maps.google.com/maps?f=q&hl=en&...c=addr&om=1

8.6k · July 31, 2007

Well, the GPS may have been wrong, it may not all have been filmed at the pole, but the look on Jeremy's face as he climbed out of the water after being pushed in was not faked.... excellent!!

Chris

1.8k · July 31, 2007

There's a photo on this page claiming to show a gpsr at the actual South Pole. It's a long page - scroll nearly halfway down and the pic is on the right hand side, or search the page for " reading 90° 00.000' " (without the double quotes). The reading on the gpsr is S 90 00.000 W 152 16.256 which I'm afraid I don't understand at all. But it seems that in Google Maps S 90 00.000 with any E or W will give the same spot, below and somewhat east of Australia.

3.9k · July 31, 2007

Hmm, having given this a bit of thought (involving a torch and football) I think I may be talking complete rubbish - both of the original statements are correct - that the sun's elevation appears constant throughout the day and that indeed there is only one true sunset/sunrise at the true poles.

Funny this, although I understand the mechanics of how the arctic circle works, this had never occurred to me before.

The sun rises at the North Pole on the spring equinox and basically spirals up very, very slowly until midsummer's day, when it starts to spiral down.

A few degrees further south, however, and you will get a proper equinox. The closer you get to the pole, the greater the difference in the length of each day either side of the equinox.

August 2, 2007

There's a photo on this page claiming to show a gpsr at the actual South Pole. It's a long page - scroll nearly halfway down and the pic is on the right hand side, or search the page for " reading 90° 00.000' " (without the double quotes). The reading on the gpsr is S 90 00.000 W 152 16.256 which I'm afraid I don't understand at all. But it seems that in Google Maps S 90 00.000 with any E or W will give the same spot, below and somewhat east of Australia.

As you move closer to the south pole, the circle of latitude will become smaller and smaller and the lines of longitude will start to converge.

In the photo, (on the website quoted) the circle of latitude around the GPSr will be about 25cm in length! Right underneath the GPSr, this distance will become very (infinitely) small at the precise South Pole and the reading will become 90 degrees.

ALL of the lines of longitude will meet at this precise spot, so it will probably be a lottery as to which one your GPSr will show - again there will be an infinite number of possibilities.

I don't know how the internal workings of the GPSr prioritise the different (many) longitudes available - it possibly has something to do with satellite signal strengths? - but I'm guessing here...

1.8k · August 2, 2007

HIghlandNick wrote:
ALL of the lines of longitude will meet at this precise spot, so it will probably be a lottery as to which one your GPSr will show - again there will be an infinite number of possibilities.

Hmm... So it's pretty well pot luck what E or W a gpsr shows at the North or South Poles? I suppose that makes sense...! A computer, faced with an infinity of possibilities, (and essentitally a gpsr is a computer), just picks something on the basis of its own internal algorithms, whatever they may be!

August 2, 2007

But it seems that in Google Maps S 90 00.000 with any E or W will give the same spot, below and somewhat east of Australia.

The Mercator map projection, which Google uses, causes locations close to the poles to be difficult to show due to the distortion. Google Maps limits maximum N/S to 85.0511287798066 degrees.

1.5k · August 2, 2007

Hope the Ruskies got all this sorted out before they placed their flag

BBC News Link: http://news.bbc.co.uk/2/hi/europe/6927395.stm

1.4k · August 2, 2007

As to the location of true north as shown by a GPS it would be nice if it was 90d 00.000'N, arbitrary E/W but something tells me it isn't that simple. The datum will probably mess things up considerably

It is that simple. The True pole is defined as the spin axis of the Earth. GPS itself doesn't actually 'think' in terms of Lat/Long. That is simply an output format for the user. Within the GPS all co-ords are calculated in 3D Cartesian form. The origin is the infinitely small point within the Earth where the line connecting the two poles intersects with the plane of the Equator. The X axis runs from there to the Equator on the zero degree meridian. The Y axis is perpendicular to the X axis and runs from the origin to the Equator at a Longitude of 90° East. The Z axis runs from the origin top the North Pole. There is a teenyweeny complication in that the Earth's Southern hemisphere is about half a metre bigger than the Northern hemisphere, but that is no problem for polar nav with GPS as everything relates to the poles and the equator, not just the equator. The units of measure are metres, not angular measure.

plus you might only get low angle satellite coverage.

Low angle satellites are an advantage, not a disadvantage for position fixing. Satellites which are elevated much more than about 60° above the local horizon are practically useless for obtaining Lat/Long, other than to assist in computing the Time and altitude elements of the four dimensions which a GPSr measures. GPS was designed very specifically to be Global and it works perfectly well in the polar regions, despite the fact that none of the satellites flies much above 56° of Latitude.

1.4k · August 2, 2007

I've always wondered - how would the early explorers know they've gotten to the pole? Scot knew he got there because he saw Amundsen's flag already there - but how did Amundsen know he'd arrived at the pole?

He set up a camp so that he could make astronav observations to measure his position beyond any doubt. There had recently been two cases of suspected scientific fraud by two American showmen who falsely claimed to have reached the North Pole and Amundsen knew that he would have to make meticulous records of his nav calcs to prove that he and his team had actually reached the South pole. Having established the exact co-ords of his station he sent his team to ski to four points around the calculated position of the pole itself, thus effectively boxing it in.

Astro nav is fairly straightforward. It's simply a matter of making timed measurements of the altitude of heavenly bodies such as the Sun, the Moon and any othe the planets and/or any of the 57 navigational stars. Amundsen's theodolite was broken by the time he reach the polar area, so he had to improvise by using his sextant as a theodolite to make the observations. Because he was ashore, and in a very mountainous continent, his sextant could not accurately identify the horizontal plane and he estimated that his fix accuracy was probably something of the order of ±½mile. He therefore ordered his skiers to make their boxin pattern large enough to be quite sure that they had certainly boxed the Pole.

Astronav as way of position-fixing is still practiced today, even after GPS has become ubiquitous. Some specialist military people are taught how to do it so that they can continue to measure position even if GPS is jammed or if their GPSrs have either failed or been lost for some reason. With some patience and perseverence, together with a good stopwatch, it is quite possible to measure position to an accuracy of a few dozen metres or so by astronav alone. Doing the numbercrunching without a programmable calculator or a computer is a pain though.

1.4k · August 2, 2007

I presume that at the north pole the sun stays at roughly the same elevation all day long, just going all the way around you. There will be a slight change as the sun's elevation rises to a max in mid summer, etc etc..

That doesn't matter much for astronav. Any measured observation makes a line of position. By repeating the measurement a couple of hours later you have an intersection of two lines of position with about 30° angle of cut. Keep repeating and your position becomes more and more accurate. You don't even need to be stationary. So long as you log your direction and distance of movement since the last fix you can compensate for the elapsed distance in the calculation. One of the reasons for the bicycle-like wheel behind the polar exploration sleds, which is an odometer, is to maintain dead-reckoning. The other use for the measured distance data is to enable running fixes to be made whenever the sun or moon is visible for a sextant or theodolite shot. It's a trick which is sometimes used in desert navigation too. 4x4 vehicle wheels spin in soft sand, so the vehicle's odometer is a lousy indicator of actual distance travelled. An old-fashioned bike-wheel odometer out the back of the vehicle is very accurate and can be a lifesaver for the prudent land navigator in harsh desert conditions when the GPS goes wonky.

1.4k · August 2, 2007

I don't know how the internal workings of the GPSr prioritise the different (many) longitudes available - it possibly has something to do with satellite signal strengths? - but I'm guessing here...

GPS doesn't 'think' in terms of Lat/Long. Instead it uses Cartesian 3D co-ords.

At the North Pole the Cartesians would be:

X:0.0m

Y:0.0m

Z:+6,356,765.9m

At the South Pole the Cartesians would be:

X:0.0m

Y:0.0m

Z:-6,359,557.8m

Owing to the natural fluctuation of GPS, especially in the absence of WAAS, both the X and Y ordinates would randomly wander a few metres either side of zero. Calculated and displayed Longitude would therefore wander randomly by the resultant of the X and Y ordinates.

By averaging lots of fixes, North Polar ice movement notwithstanding, an accurate fix could be computed, but you'd have to do so with the original Cartesians, not Lat/Longs as non zero X&Y would tend to cancel +ve figures with -ve ones and vice-versa, whereas non 90° Latitudes could only be <90° so averaging Latitude readouts would always produce a Latitude less than 90°.

August 3, 2007

I don't know how the internal workings of the GPSr prioritise the different (many) longitudes available - it possibly has something to do with satellite signal strengths? - but I'm guessing here...

GPS doesn't 'think' in terms of Lat/Long. Instead it uses Cartesian 3D co-ords.

At the North Pole the Cartesians would be:

X:0.0m

Y:0.0m

Z:+6,356,765.9m

At the South Pole the Cartesians would be:

X:0.0m

Y:0.0m

Z:-6,359,557.8m

Owing to the natural fluctuation of GPS, especially in the absence of WAAS, both the X and Y ordinates would randomly wander a few metres either side of zero. Calculated and displayed Longitude would therefore wander randomly by the resultant of the X and Y ordinates.

By averaging lots of fixes, North Polar ice movement notwithstanding, an accurate fix could be computed, but you'd have to do so with the original Cartesians, not Lat/Longs as non zero X&Y would tend to cancel +ve figures with -ve ones and vice-versa, whereas non 90° Latitudes could only be <90° so averaging Latitude readouts would always produce a Latitude less than 90°.

Precisely.

August 4, 2007

I love these sorts of threads, they allow me to learn so much.

Thanks, Forester.

definitive GPS location of the north/south pole

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