# GPS accuracy at the South Pole, circa 1911-1912 **URL:** \ **Category:** Factual Questions\ **Created:** [July 29, 2022, 10:15am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771 "2022-07-29T10:15:05Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Keeve](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Keeve](https://boards.straightdope.com/u/Keeve)\ **Post date:** [July 29, 2022, 10:15am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/1 "2022-07-29T10:15:05Z")
When Amundsen reached the South Pole in Dec 1911, and stuck a flag in the ground declaring “This is the South Pole” (not his actual words, of course), surely what he _meant_ was “This is the South Pole give or take X.” How far is X? When Scott got there a month later, was his reaction, “Oh, crap,” or was it more like, “Ummm… no. The Pole is over _here_.”? I understand that they had various optical (a/k/a analog) instruments for measuring the positions of the stars and sun and such, but how accurate were they? ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [July 29, 2022, 10:41am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/2 "2022-07-29T10:41:00Z")
There was no GPS back then, at the South Pole or anywhere. Amundsen and his colleagues manually used a sextant with artificial horizons. [From his book,] the tent with the flag on it was approximately 89º 58.5’ S, and from there they walked four nautical miles south, passing the pole at a distance of several hundred metres or less and circled around it. So one and a half miles is the accuracy they were getting near the pole, given what they had to work with and how they were observing the meridian altitude of the Sun. [Other stars “and such”? In broad daylight??] ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [July 29, 2022, 11:02am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/3 "2022-07-29T11:02:37Z")
What they did was, when they thought they were quite close to the pole, they planted a flag and walked due West, scribing a line in the snow. After a short time they returned to their flag having drawn a circle with the pole at its centre. It was then just a matter of bisecting the circle as accurately as they could at various intervals around the circumference (the more the better). Where the bisecting lines crossed each other at the centre of the circle was the position of the pole to a very high degree of accuracy. 😉 ---
**Author:** ![Keeve](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@Keeve](https://boards.straightdope.com/u/Keeve)\ **Post date:** [July 29, 2022, 11:41am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/4 "2022-07-29T11:41:47Z")
So if their circle was a few hundred meters in diameter, then I suppose that all those lines intersected no more than a few dozen meters from each other. That’s pretty accurate, in my view. Thanks! BTW, my use of “GPS” in the thread title was mostly tongue-in-cheek, but also quite literal. They most certainly did have a Global Positioning System, except it used sextants and the sun, instead of the radios and satellites that we’re used to. (But my mentioning “stars… and such” was a bad mistake. Sorry.) ---
**Author:** ![smithsb](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/smithsb/32/12107_2.png) [@smithsb](https://boards.straightdope.com/u/smithsb)\ **Post date:** [July 29, 2022, 12:37pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/5 "2022-07-29T12:37:51Z")
You’re good. Our sun is a star. My question is the Earth’s wobble. Isn’t the “exact” position variable over a short distance and by how much? ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [July 29, 2022, 3:06pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/6 "2022-07-29T15:06:29Z")
> [@Keeve](#): > > So if their circle was a few hundred meters in diameter, then I suppose that all those lines intersected no more than a few dozen meters from each other. That’s pretty accurate, in my view. Thanks! “I say, son, it’s a joke, you’re supposed to laugh!” > [@smithsb](#): > > My question is the Earth’s wobble. Isn’t the “exact” position variable over a short distance and by how much? There are some wobbles and oscillations > **[Polar motion](https://en.wikipedia.org/wiki/Polar_motion)** > > Polar motion of the Earth is the motion of the Earth's rotational axis relative to its crust.: 1  This is measured with respect to a reference frame in which the solid Earth is fixed (a so-called Earth-centered, Earth-fixed or ECEF reference frame). This variation is a few meters on the surface of the Earth. > Polar motion is defined relative to a conventionally defined reference axis, the CIO (Conventional International Origin), being the pole's average location over the year 1900. It consists of... with an amplitude of a few metres. ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [July 29, 2022, 4:48pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/7 "2022-07-29T16:48:37Z")
At the present day South Pole station they remark the exact pole each year. The old markers are left standing and you can see thew progression [https://www.southpolestation.com/trivia/2020marker.html](https://www.southpolestation.com/trivia/2020marker.html) ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [July 29, 2022, 4:50pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/8 "2022-07-29T16:50:19Z")
Wait, isn’t there a red-and-white barbershop striped pole at the Pole? ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [July 29, 2022, 4:51pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/9 "2022-07-29T16:51:57Z")
That’s the North Pole. Sheesh… stay informed why don’t you… ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [July 29, 2022, 4:52pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/10 "2022-07-29T16:52:54Z")
I thought there was one at both Poles (actually, just the ends of the same pole). ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [July 29, 2022, 4:55pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/11 "2022-07-29T16:55:36Z")
Used to be. But you know how many tons of meteorites accumulate on Earth every year? It’s growing. They anchored the top of the pole, so at the southern end the Earth’s surface has now grown beyond the end. Which is fine. It’s not used to literally pivot the rotation of the Earth. Not anymore, anyhow. ---
**Author:** ![Slithy\_Tove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slithy_tove/32/18248_2.png) [@Slithy\_Tove](https://boards.straightdope.com/u/Slithy_Tove)\ **Post date:** [July 29, 2022, 5:00pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/12 "2022-07-29T17:00:59Z")
Not a barber pole: a gyroscope put there by [perpetual motion enthusiasts.](https://physics.stackexchange.com/questions/471077/what-happens-energy-wise-if-you-put-a-gyroscope-at-the-north-pole) ---
**Author:** ![Mk\_VII](https://avatars.discourse-cdn.com/v4/letter/m/5f9b8f/32.png) [@Mk\_VII](https://boards.straightdope.com/u/Mk_VII)\ **Post date:** [July 29, 2022, 5:40pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/13 "2022-07-29T17:40:35Z")
They found Amundsen’s pole, and the message he left for them, and calculated, rightly or wrongly, that he was half a mile or so short, and planted their own flag at what they thought was the right spot. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [July 29, 2022, 5:57pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/14 "2022-07-29T17:57:54Z")
How did they flatten out the giant ice wall at the edge of the earth for those photos? ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [July 29, 2022, 6:43pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/15 "2022-07-29T18:43:55Z")
> [@Richard\_Pearse](#): > > they planted a flag and walked due West, scribing a line in the snow. How did they know which direction was due West? ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [July 29, 2022, 6:59pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/16 "2022-07-29T18:59:46Z")
> [@Keeve](#): > > When Scott got there a month later, was his reaction, “Oh, crap,” or was it more like, “Ummm… no. The Pole is over _here_.”? It was "Race to the Pole? There was never a race to the pole, mine was purely a scientific expedition! " Causing him to man haul a load of specimens, and causing the death of five men in this poorly planned expedition, and oddly, making Scott a great Hero to the British. Actual words- _“The worst has happened […] All the day dreams must go […] Great God! This is an awful place”_ ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [July 29, 2022, 9:55pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/17 "2022-07-29T21:55:48Z")
Did I need more winkie smilies? ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [July 29, 2022, 10:21pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/18 "2022-07-29T22:21:08Z")
I guess so. I took your post at face value. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [July 29, 2022, 10:27pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/19 "2022-07-29T22:27:11Z")
Sorry. The question seemed to be answered by the post above mine. As you point out, you can’t know West to the precision needed to do what I suggested and if you did then you would also know South and North so you could just go South to the pole. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [July 29, 2022, 11:03pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/20 "2022-07-29T23:03:39Z")
> [@DPRK](#): > > the tent with the flag on it was approximately 89º 58.5’ S, and from there they walked four nautical miles south Shouldn’t they have been able to do better than that? Google says that modern sextants can achieve 0.1’ accuracy. Maybe sextants from 1911 were much worse, but the technology hasn’t changed that much, and presumably they’d be using the highest quality equipment available. Walking west or any other direction is easy. A shadow at noon always points south. Derive the rest of the compass rose from that. **Richard\_Pearse** may have been being sarcastic, but they could have easily used the approach of taking a few readings around a circle and finding the center via intersection. [Next page](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771.md?page=2)