# 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:** 17\ **Page:** 2
**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, 11:30pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/21 "2022-07-29T23:30:10Z")
I do not think the issue was with sextant accuracy. Here is the report from the book: > [@](#): > > Captain Roald Amundsen, > > At your request I shall here give briefly the result of my examination of the observations from your South Pole Expedition. My calculations are based on the longitude for Framheim given to me by Lieutenant Prestrud, 163° 37’ W. of Greenwich. He describes this longitude as provisional, but only to such an extent that the final result cannot differ appreciably from it. My own results may also be somewhat modified on a final treatment of the material. But these modifications, again, will only be immaterial, and, in any case, will not affect the result of the investigations given below as to the position of the two Polar stations. > > At the first Polar station, on December 15, 1911, eighteen altitudes of the sun were taken in all with each of the expedition’s sextants. The latitude calculated from these altitudes is, on an average of both sextants, very near 89° 54’, with a mean error of ±2’. The longitude calculated from the altitudes is about 7t (105°) E.; but, as might be expected in this high latitude, the aberrations are very considerable. We may, however, assume with great certainty that this station lies between lat. 89° 52’ and 89° 56’ S., and between long. 90° and 120° E. > > The variation of the compass at the first Polar station was determined by a series of bearings of the sun. This gives us the absolute direction of the last day’s line of route. The length of this line was measured as five and a half geographical miles. With the help of this we are able to construct for Polheim a field of the same form and extent as that within which the first Polar station must lie. > > At Polheim, during a period of twenty-four hours (December 16 — 17), observations were taken every hour with one of the sextants. The observations show an upper culmination altitude of 28° 19.2’, and a resulting lower culmination altitude of 23° 174’. These combining the above two altitudes, an equal error on the same side in each will have no influence on the result. The combination gives a latitude of 89° 58.6’. That this result must be nearly correct is confirmed by the considerable displacement of the periods of culmination which is indicated by the series of observations, and which in the immediate neighbourhood of the Pole is caused by the change in the sun’s declination. On the day of the observations this displacement amounted to thirty minutes in 89° 57’, forty-six minutes in 89° 58’, and over an hour and a half in 89° 59’. The upper culmination occurred so much too late, and the lower culmination so much too early. The interval between these two periods was thus diminished by double the amount of the displacements given. Now the series of observations shows that the interval between the upper and the lower culmination amounted at the most to eleven hours; the displacement of the periods of culmination was thus at least half an hour. It results that Polheim must lie south of 89° 57’, while at the same time we may assume that it cannot lie south of 89° 59’. The moments of culmination could, of course, only be determined very approximately, and in the same way the observations as a whole are unserviceable for the determination of longitude. It may, however, be stated with some certainty that the longitude must be between 30° and 75° E. The latitude, as already mentioned, is between 89° 57’ and 89° 59’, and the probable position of Polheim may be given roughly as lat. 89° 58.5’ S., and long. 60° E. > > On the accompanying sketch-chart the letters abcd indicate the field within which the first Polar station must lie; ABCD is the field which is thereby assigned to Polheim; EFGH the field within which Polheim must lie according to the observations taken on the spot itself; P the probable position of Polheim, and L the resulting position of the first Polar station. The position thus assigned to the latter agrees as well as could be expected with the average result of the observations of December 15. According to this, Polheim would be assumed to lie one and a half geographical miles, or barely three kilometres, from the South Pole, and certainly not so much as six kilometres from it. > > From your verbal statement I learn that Helmer Hanssen and Bjaaland walked four geographical miles from Polheim in the direction taken to be south on the basis of the observations. On the chart the letters efgh give the field within which the termination of their line of route must lie. It will be seen from this that they passed the South Pole at a distance which, on the one hand, can hardly have been so great as two and a half kilometres, and on the other, hardly so great as two kilometres; that, if the assumed position of Polheim be correct, they passed the actual Pole at a distance of between 400 and 600 metres; and that it is very probable that they passed the actual Pole at a distance of a few hundred metres, perhaps even less. > > I am, etc., > > (Signed) Anton Alexander. > > Christiania, > > September 22, 1912. Here is Amundsen’s account: > [@](#): > > The first thing we did — Hanssen and I — was to set about arranging a lot of trifling matters; there was something to be done here, something there, and above all we had to be ready for the series of observations we were to carry out together, so as to get as accurate a determination of our position as possible. The first observation told us at once how necessary this was. For it turned out that this, instead of giving us a greater altitude than the midnight observation, gave us a smaller one, and it was then clear that we had gone out of the meridian we thought we were following. Now the first thing to be done was to get our north and south line and latitude determined, so that we could find our position once more. Luckily for us, the weather looked as if it would hold. We measured the sun’s altitude at every hour from 6 a.m. to 7 p.m., and from these observations found, with some degree of certainty, our latitude and the direction of the meridian. > > By nine in the morning we began to expect the return of our comrades; according to our calculation they should then have covered the distance — twenty-five miles. It was not till ten o’clock that Hanssen made out the first black dot on the horizon, and not long after the second and third appeared. We both gave a sigh of relief as they came on; almost simultaneously the three arrived at the tent. We told them the result of our observations up to that time; it looked as if our camp was in about 89° 54’ 30’’ S., and that with our encircling we had therefore included the actual Pole. With this result we might very well have been content, but as the weather was so good and gave the impression that it would continue so, and our store of provisions proved on examination to be very ample, we decided to go on for the remaining ten kilometres (five and a half geographical miles), and get our position determined as near to the Pole as possible. Meanwhile the three wanderers turned in — not so much because they were tired, as because it was the right thing to do — and Hanssen and I continued the series of observations. > > In the afternoon we again went very carefully through our provision supply before discussing the future. The result was that we had food enough for ourselves and the dogs for eighteen days. The surviving sixteen dogs were divided into two teams of eight each, and the contents of Bjaaland’s sledge were shared between Hanssen’s and Wisting’s. The abandoned sledge was set upright in the snow, and proved to be a splendid mark. The sledge-meter was screwed to the sledge, and we left it there; our other two were quite sufficient for the return journey; they had all shown themselves very accurate. A couple of empty provision cases were also left behind. I wrote in pencil on a piece of case the information that our tent — “Polheim” — would be found five and a half geographical miles north-west quarter west by compass from the sledge. Having put all these things in order the same day, we turned in, very well satisfied. > > Early next morning, December 16, we were on our feet again. Bjaaland, who had now left the company of the drivers and been received with jubilation into that of the forerunners, was immediately entrusted with the honourable task of leading the expedition forward to the Pole itself. I assigned this duty, which we all regarded as a distinction, to him as a mark of gratitude to the gallant Telemarkers for their pre-eminent work in the advancement of ski spot. The leader that day had to keep as straight as a line, and if possible to follow the direction of our meridian. A little way after Bjaaland came Hassel, then Hanssen, then Wisting, and I followed a good way behind. I could thus check the direction of the march very accurately, and see that no great deviation was made. Bjaaland on this occasion showed himself a matchless forerunner; he went perfectly straight the whole time. Not once did he incline to one side or the other, and when we arrived at the end of the distance, we could still clearly see the sledge we had set up and take its bearing. This showed it to be absolutely in the right direction. > > It was 11 a.m. when we reached our destination. While some of us were putting up the tent, others began to get everything ready for the coming observations. A solid snow pedestal was put up, on which the artificial horizon was to be placed, and a smaller one to rest the sextant on when it was not in use. At 11.30 a.m. the first observation was taken. We divided ourselves into two parties — Hanssen and I in one, Hassel and Wisting in the other. While one party slept, the other took the observations, and the watches were of six hours each. The weather was altogether grand, though the sky was not perfectly bright the whole time. A very light, fine, vaporous curtain would spread across the sky from time to time, and then quickly disappear again. This film of cloud was not thick enough to hide the sun, which we could see the whole time, but the atmosphere seemed to be disturbed. The effect of this was that the sun appeared not to change its altitude for several hours, until it suddenly made a jump. > > Observations were now taken every hour through the whole twenty-four. It was very strange to turn in at 6 p.m., and then on turning out again at midnight to find the sun apparently still at the same altitude, and then once more at 6 a.m. to see it still no higher. The altitude had changed, of course, but so slightly that it was imperceptible with the naked eye. To us it appeared as though the sun made the circuit of the heavens at exactly the same altitude. The times of day that I have given here are calculated according to the meridian of Framheim; we continued to reckon our time from this. The observations soon told us that we were not on the absolute Pole, but as close to it as we could hope to get with our instruments. The observations, which have been submitted to Mr. Anton Alexander, will be published, and the result given later in this book. > > On December 17 at noon we had completed our observations, and it is certain that we had done all that could be done. In order if possible to come a few inches nearer to the actual Pole, Hanssen and Bjaaland went out four geographical miles (seven kilometres) in the direction of the newly found meridian. ---
**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, 11:55pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/22 "2022-07-29T23:55:39Z")
So, near the pole the altitude of the sun changes pretty slowly, and they took 24 hours to make a set of observations. Also, the mist in the air caused the image of the sun to jump around, which has to be averaged out. Note that they knew they were a couple of miles north; they theoretically could have repeated the process. The declination of the sun was changing by a couple of minutes per day; on the other hand they had all the noise to contend with, and who knows how much mathematical sophistication they were willing to put into it. Note that they were already getting a mean error of 2’ at 89° 54’; maybe they figured they could not do any better. > [@Dr.Strangelove](#): > > A shadow at noon always points south …which is super useful _if you can figure out the moment of noon_ 🙂 ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 29, 2022, 11:58pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/23 "2022-07-29T23:58:41Z")
> [@Dr.Strangelove](#): > > Walking west or any other direction is easy. A shadow at noon always points south. OK, but determining noon requires knowing your latitude, and knowing your latitude requires knowing your position relative 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 30, 2022, 12:10am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/24 "2022-07-30T00:10:28Z")
> [@DPRK](#): > > which is super useful _if you can figure out the moment of noon_ Sure. But the closer you get to the pole, the less accurate the heading needs to be. I don’t see how the altitude changing slowly really changes things. There will be a high and a low point, and your latitude relative to the pole will be half the difference. Repeat as many times as needed. The aberrations sound like a bigger deal, if they were causing an error of 2’. I suppose that gets worse when all readings are only ~23° from the horizon. It’s going through a lot of atmosphere at that point. Bringing a clock along would have made some things easier, but I suppose that wasn’t in the cards given the environmental conditions. > [@Chronos](#): > > OK, but determining noon requires knowing your latitude Noon is just the point when the sun is highest in the sky. Of course, that breaks down at the pole, and gets less accurate as you get closer. But you could perform readings farther away and determine a heading based on distant landmarks. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [July 30, 2022, 12:25am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/25 "2022-07-30T00:25:55Z")
> [@Dr.Strangelove](#): > > Walking west or any other direction is easy. A shadow at noon always points south. And how do you know it’s noon? The sun just goes around in a circle, height changing only with the season. How do you know what time zone you are in (assuming they had time zones then). In fact, noon would be defined by the time your shadow points due south. ---
**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 30, 2022, 12:30am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/26 "2022-07-30T00:30:19Z")
The time zone matters if you want to know when it’s 12:00. But noon (and in case it’s not clear, I’m talking _solar noon_) is just when the sun is at its highest point. As I mentioned, that breaks down when you’re _exactly_ at the pole, and your ability to discern the time of the highest point gets worse as you get closer, but there is nevertheless still a highest point if you’re any finite distance from the pole. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [July 30, 2022, 12:32am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/27 "2022-07-30T00:32:56Z")
They did stay in one spot for 24 hours and observe the (very slowly changing) altitude of the sun; I understood from the quoted paragraphs that the data was noisy enough that they determined they were at the limit of their precision, at the same time there was no doubt they were not exactly at the pole. They decided just to walk in a circle around where the pole was sure to be. ---
**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 30, 2022, 12:52am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/28 "2022-07-30T00:52:56Z")
Putting up a tent and a foucault pendulum wouldn’t have worked. The staff down there did that [in 2001](https://www.southpolestation.com/trivia/00s/southpolefoucault.html) and they had to keep tweaking it over and over. ---
**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 30, 2022, 12:58am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/29 "2022-07-30T00:58:37Z")
If they had a clock of modest accuracy (could keep decent time over a 1-day period), using the phase of the sun might have better results. That is, determine the high and low points, then determine the time that the sun passes through the halfway mark (both rising and falling). Noon (or midnight) is halfway between those points. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [July 30, 2022, 2:28am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/30 "2022-07-30T02:28:09Z")
But greatest altitude will not coincide with the moment of transit, even pretty close but not exactly on the pole. Of course, they had enough observations to work everything out, which is exactly what Anton Alexander did if you read what he wrote, but he says that “The moments of culmination could, of course, only be determined very approximately” and does not presume any more precision than that the tent was “between 89° 57’ and 89° 59’”. On or very near the pole itself, of course the altitude would just gradually keep increasing so you would not try to observe any up and down oscillations. Perhaps that is one reason why they did not try to repeat 24 hours of observation nearer the pole; they just walked south (as best they could determine it) from the tent and called it good enough. ---
**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 30, 2022, 3:11am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/31 "2022-07-30T03:11:33Z")
Sorry, haven’t had a chance to more than skim the passages yet. I agree that there are some other factors they’d have to correct for, though I’m not sure why you’d stop observing oscillations except when right at the pole. Even tiny deviations should be easily measurable; in fact they’d get more accurate as they got closer since the amount of atmosphere being passed through would vary less. Since they arrived at the pole on Dec 11, the sun wouldn’t be quite at 23.5°, though I don’t have a table handy to tell me what it would have been. Wouldn’t be much different, though that close to the pole it might have been significant. At any rate, all easily determined via table. Regardless, if their mean error was 2’, then they aren’t going to get too much closer than that unless they average over a very long period. Too bad they didn’t have the (not Sun) stars available, but I guess it gets pretty chilly down there in June… ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [July 30, 2022, 10:08am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/32 "2022-07-30T10:08:09Z")
At the south pole, shadows all point north all the time, don’t they? ---
**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 30, 2022, 11:08pm UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/33 "2022-07-30T23:08:24Z")
Yep so you could wait for your shadow to point north then you’d know you were at the pole. 😉 😉 ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [July 31, 2022, 12:06am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/34 "2022-07-31T00:06:35Z")
> [@Dr.Strangelove](#): > > Sorry, haven’t had a chance to more than skim the passages yet. I agree that there are some other factors they’d have to correct for, though I’m not sure why you’d stop observing oscillations except when right at the pole. Even tiny deviations should be easily measurable; in fact they’d get more accurate as they got closer since the amount of atmosphere being passed through would vary less. The trigonometry to figure out exactly how close you can get to the pole is not too bad, but let’s run some numbers through the computer first. Ignoring refraction and other issues, let’s print out the apparent altitude of the Sun every hour at the pole: > **Summary** > > ```x > Target body name: Sun (10) {source: DE441} > Center body name: Earth (399) {source: DE441} > Center-site name: (user defined site below) > ******************************************************************************* > Start time : A.D. 1911-Dec-15 00:00:00.0000 UT > Stop time : A.D. 1911-Dec-16 00:00:00.0000 UT > Step-size : 60 minutes > ******************************************************************************* > Target pole/equ : IAU_SUN {East-longitude positive} > Target radii : 696000.0 x 696000.0 x 696000.0 k{Equator, meridian, pole} > Center geodetic : 60.0000000,-90.000000,3.919E-13 {E-lon(deg),Lat(deg),Alt(km)} > Center cylindric: 60.0000000,3.9186E-13,-6356.752 {E-lon(deg),Dxy(km),Dz(km)} > Center pole/equ : ITRF93 {East-longitude positive} > Center radii : 6378.1 x 6378.1 x 6356.8 km {Equator, meridian, pole} > Target primary : Sun > Vis. interferer : MOON (R_eq= 1737.400) km {source: DE441} > Rel. light bend : Sun, EARTH {source: DE441} > Rel. lght bnd GM: 1.3271E+11, 3.9860E+05 km^3/s^2 > Atmos refraction: NO (AIRLESS) > RA format : HMS > Time format : CAL > EOP file : eop.220728.p221021 > EOP coverage : DATA-BASED 1962-JAN-20 TO 2022-JUL-28. PREDICTS-> 2022-OCT-20 > Units conversion: 1 au= 149597870.700 km, c= 299792.458 km/s, 1 day= 86400.0 s > Table cut-offs 1: Elevation (-90.0deg=NO ),Airmass (>38.000=NO), Daylight (NO ) > Table cut-offs 2: Solar elongation ( 0.0,180.0=NO ),Local Hour Angle( 0.0=NO ) > Table cut-offs 3: RA/DEC angular rate ( 0.0=NO ) > ********************************************************************************************************* > Date__(UT)__HR:MN R.A.__(a-apparent)__DEC Azi____(a-app)___Elev Sky_motion Sky_mot_PA RelVel-ANG > ********************************************************************************************************* > $$SOE > 1911-Dec-15 00:00 *m 17 24 43.37 -23 12 09.4 273.384665 23.202617 2.5440417 93.500378 -0.301779 > 1911-Dec-15 01:00 *m 17 24 54.43 -23 12 18.7 258.389645 23.205199 2.5440698 93.482237 -0.301202 > 1911-Dec-15 02:00 *m 17 25 05.48 -23 12 28.0 243.394627 23.207767 2.5440978 93.464092 -0.300625 > 1911-Dec-15 03:00 *m 17 25 16.53 -23 12 37.2 228.399612 23.210322 2.5441256 93.445945 -0.300050 > 1911-Dec-15 04:00 *m 17 25 27.58 -23 12 46.3 213.404599 23.212864 2.5441534 93.427795 -0.299476 > 1911-Dec-15 05:00 *m 17 25 38.64 -23 12 55.4 198.409588 23.215392 2.5441811 93.409642 -0.298903 > 1911-Dec-15 06:00 *m 17 25 49.69 -23 13 04.5 183.414579 23.217907 2.5442088 93.391485 -0.298331 > 1911-Dec-15 07:00 *m 17 26 00.75 -23 13 13.5 168.419573 23.220409 2.5442363 93.373326 -0.297760 > 1911-Dec-15 08:00 *m 17 26 11.80 -23 13 22.4 153.424569 23.222897 2.5442637 93.355165 -0.297190 > 1911-Dec-15 09:00 *m 17 26 22.86 -23 13 31.3 138.429567 23.225372 2.5442911 93.337000 -0.296622 > 1911-Dec-15 10:00 *m 17 26 33.91 -23 13 40.2 123.434567 23.227833 2.5443184 93.318832 -0.296054 > 1911-Dec-15 11:00 *m 17 26 44.97 -23 13 49.0 108.439569 23.230281 2.5443455 93.300661 -0.295487 > 1911-Dec-15 12:00 *m 17 26 56.03 -23 13 57.8 93.444574 23.232715 2.5443726 93.282488 -0.294921 > 1911-Dec-15 13:00 *m 17 27 07.09 -23 14 06.5 78.449581 23.235136 2.5443996 93.264312 -0.294356 > 1911-Dec-15 14:00 *m 17 27 18.15 -23 14 15.2 63.454590 23.237544 2.5444266 93.246132 -0.293792 > 1911-Dec-15 15:00 *m 17 27 29.21 -23 14 23.8 48.459601 23.239938 2.5444534 93.227950 -0.293229 > 1911-Dec-15 16:00 *m 17 27 40.26 -23 14 32.3 33.464614 23.242319 2.5444801 93.209766 -0.292667 > 1911-Dec-15 17:00 *m 17 27 51.32 -23 14 40.9 18.469629 23.244686 2.5445068 93.191578 -0.292105 > 1911-Dec-15 18:00 *m 17 28 02.39 -23 14 49.3 3.474647 23.247040 2.5445334 93.173388 -0.291545 > 1911-Dec-15 19:00 *m 17 28 13.45 -23 14 57.8 348.479666 23.249381 2.5445598 93.155194 -0.290986 > 1911-Dec-15 20:00 *m 17 28 24.51 -23 15 06.1 333.484688 23.251708 2.5445862 93.136999 -0.290427 > 1911-Dec-15 21:00 *m 17 28 35.57 -23 15 14.5 318.489712 23.254022 2.5446126 93.118800 -0.289870 > 1911-Dec-15 22:00 *m 17 28 46.63 -23 15 22.8 303.494738 23.256322 2.5446388 93.100599 -0.289313 > 1911-Dec-15 23:00 *m 17 28 57.70 -23 15 31.0 288.499766 23.258609 2.5446649 93.082395 -0.288758 > 1911-Dec-16 00:00 *m 17 29 08.76 -23 15 39.2 273.504796 23.260882 2.5446910 93.064188 -0.288203 > $$EOE > ********************************************************************************************************* > > ``` As expected, it slowly increases. Now at 89° 59’: > **Summary** > > ```x > 1911-Dec-15 00:00 *m 17 24 43.37 -23 12 09.4 118.757074 23.194599 2.5440474 93.500459 -0.301985 > 1911-Dec-15 01:00 *m 17 24 54.43 -23 12 18.7 103.762732 23.201235 2.5440727 93.482331 -0.301430 > 1911-Dec-15 02:00 *m 17 25 05.48 -23 12 28.0 88.767919 23.208127 2.5440978 93.464193 -0.300861 > 1911-Dec-15 03:00 *m 17 25 16.53 -23 12 37.2 73.772622 23.214981 2.5441227 93.446046 -0.300276 > 1911-Dec-15 04:00 *m 17 25 27.58 -23 12 46.3 58.776860 23.221504 2.5441478 93.427889 -0.299678 > 1911-Dec-15 05:00 *m 17 25 38.64 -23 12 55.4 43.780683 23.227426 2.5441731 93.409722 -0.299066 > 1911-Dec-15 06:00 *m 17 25 49.69 -23 13 04.5 28.784170 23.232515 2.5441989 93.391547 -0.298445 > 1911-Dec-15 07:00 *m 17 26 00.75 -23 13 13.5 13.787425 23.236595 2.5442253 93.373365 -0.297817 > 1911-Dec-15 08:00 *m 17 26 11.80 -23 13 22.4 358.790565 23.239560 2.5442524 93.355177 -0.297186 > 1911-Dec-15 09:00 *m 17 26 22.86 -23 13 31.3 343.793717 23.241376 2.5442801 93.336986 -0.296557 > 1911-Dec-15 10:00 *m 17 26 33.91 -23 13 40.2 328.797007 23.242089 2.5443085 93.318792 -0.295933 > 1911-Dec-15 11:00 *m 17 26 44.97 -23 13 49.0 313.800551 23.241817 2.5443375 93.300599 -0.295318 > 1911-Dec-15 12:00 *m 17 26 56.03 -23 13 57.8 298.804450 23.240746 2.5443670 93.282407 -0.294715 > 1911-Dec-15 13:00 *m 17 27 07.09 -23 14 06.5 283.808778 23.239115 2.5443967 93.264217 -0.294128 > 1911-Dec-15 14:00 *m 17 27 18.15 -23 14 15.2 268.813581 23.237200 2.5444266 93.246031 -0.293557 > 1911-Dec-15 15:00 *m 17 27 29.20 -23 14 23.8 253.818874 23.235294 2.5444563 93.227850 -0.293003 > 1911-Dec-15 16:00 *m 17 27 40.26 -23 14 32.3 238.824637 23.233692 2.5444858 93.209672 -0.292465 > 1911-Dec-15 17:00 *m 17 27 51.32 -23 14 40.9 223.830819 23.232664 2.5445148 93.191498 -0.291942 > 1911-Dec-15 18:00 *m 17 28 02.39 -23 14 49.3 208.837341 23.232441 2.5445432 93.173327 -0.291431 > 1911-Dec-15 19:00 *m 17 28 13.45 -23 14 57.8 193.844101 23.233198 2.5445708 93.155157 -0.290928 > 1911-Dec-15 20:00 *m 17 28 24.51 -23 15 06.1 178.850979 23.235044 2.5445976 93.136987 -0.290431 > 1911-Dec-15 21:00 *m 17 28 35.57 -23 15 14.5 163.857850 23.238012 2.5446235 93.118815 -0.289934 > 1911-Dec-15 22:00 *m 17 28 46.63 -23 15 22.8 148.864588 23.242056 2.5446486 93.100639 -0.289434 > 1911-Dec-15 23:00 *m 17 28 57.70 -23 15 31.0 133.871076 23.247059 2.5446730 93.082458 -0.288927 > 1911-Dec-16 00:00 *m 17 29 08.76 -23 15 39.2 118.877216 23.252834 2.5446966 93.064270 -0.288409 > > ``` It goes up and down, all right. But let’s be at 89° 59’.5 : > **Summary** > > ```x > 1911-Dec-15 00:00 *m 17 24 43.37 -23 12 09.4 118.857132 23.198595 2.5440446 93.500418 -0.301882 > 1911-Dec-15 01:00 *m 17 24 54.43 -23 12 18.7 103.862452 23.203202 2.5440713 93.482284 -0.301316 > 1911-Dec-15 02:00 *m 17 25 05.48 -23 12 28.0 88.867539 23.207932 2.5440978 93.464143 -0.300743 > 1911-Dec-15 03:00 *m 17 25 16.53 -23 12 37.2 73.872384 23.212637 2.5441242 93.445995 -0.300163 > 1911-Dec-15 04:00 *m 17 25 27.58 -23 12 46.3 58.876998 23.217172 2.5441506 93.427842 -0.299577 > 1911-Dec-15 05:00 *m 17 25 38.64 -23 12 55.4 43.881405 23.221399 2.5441771 93.409682 -0.298985 > 1911-Dec-15 06:00 *m 17 25 49.69 -23 13 04.5 28.885645 23.225204 2.5442038 93.391516 -0.298388 > 1911-Dec-15 07:00 *m 17 26 00.75 -23 13 13.5 13.889770 23.228499 2.5442308 93.373346 -0.297789 > 1911-Dec-15 08:00 *m 17 26 11.80 -23 13 22.4 358.893839 23.231229 2.5442581 93.355171 -0.297188 > 1911-Dec-15 09:00 *m 17 26 22.86 -23 13 31.3 343.897914 23.233378 2.5442856 93.336993 -0.296589 > 1911-Dec-15 10:00 *m 17 26 33.91 -23 13 40.2 328.902058 23.234969 2.5443134 93.318812 -0.295993 > 1911-Dec-15 11:00 *m 17 26 44.97 -23 13 49.0 313.906331 23.236060 2.5443415 93.300630 -0.295402 > 1911-Dec-15 12:00 *m 17 26 56.03 -23 13 57.8 298.910781 23.236744 2.5443698 93.282447 -0.294818 > 1911-Dec-15 13:00 *m 17 27 07.09 -23 14 06.5 283.915446 23.237141 2.5443982 93.264264 -0.294242 > 1911-Dec-15 14:00 *m 17 27 18.15 -23 14 15.2 268.920351 23.237387 2.5444266 93.246082 -0.293674 > 1911-Dec-15 15:00 *m 17 27 29.21 -23 14 23.8 253.925501 23.237631 2.5444549 93.227900 -0.293116 > 1911-Dec-15 16:00 *m 17 27 40.26 -23 14 32.3 238.930887 23.238019 2.5444830 93.209719 -0.292566 > 1911-Dec-15 17:00 *m 17 27 51.32 -23 14 40.9 223.936485 23.238686 2.5445108 93.191538 -0.292024 > 1911-Dec-15 18:00 *m 17 28 02.39 -23 14 49.3 208.942254 23.239748 2.5445383 93.173357 -0.291488 > 1911-Dec-15 19:00 *m 17 28 13.45 -23 14 57.8 193.948143 23.241293 2.5445653 93.155176 -0.290957 > 1911-Dec-15 20:00 *m 17 28 24.51 -23 15 06.1 178.954093 23.243376 2.5445919 93.136993 -0.290429 > 1911-Dec-15 21:00 *m 17 28 35.57 -23 15 14.5 163.960040 23.246013 2.5446180 93.118807 -0.289902 > 1911-Dec-15 22:00 *m 17 28 46.63 -23 15 22.8 148.965923 23.249182 2.5446437 93.100619 -0.289374 > 1911-Dec-15 23:00 *m 17 28 57.70 -23 15 31.0 133.971682 23.252823 2.5446689 93.082427 -0.288842 > 1911-Dec-16 00:00 *m 17 29 08.76 -23 15 39.2 118.977268 23.256845 2.5446938 93.064229 -0.288306 > > ``` It looks like it is (barely) monotonically increasing. Preliminary conclusion: if the sun continuously rises, you must be pretty close to the pole, but maybe not exactly (you could be up to half a mile away). If you observe oscillations, you did not make it within half a mile of the pole. On 15 December 1911, 60°E. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [July 31, 2022, 12:13am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/35 "2022-07-31T00:13:35Z")
> [@Chronos](#): > > OK, but determining noon requires knowing your latitude Latitude or longitude? ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [July 31, 2022, 12:57am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/36 "2022-07-31T00:57:52Z")
> [@mixdenny](#): > > At the present day South Pole station they remark the exact pole each year. Note that this is because the ice moves, not an actual movement of the pole. It says so at the link, but they don’t emphasize it. If you missed that point, you might get the idea that the pole is actually moving in a straight line. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 31, 2022, 11:25am UTC](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771/37 "2022-07-31T11:25:47Z")
> [@Saint\_Cad](#): > > Latitude or longitude? Longitude. Even when I stop to think about it, I still often get those two mixed up. And I think that when I made that post, I didn’t stop to think about it. Thanks for catching that. [Previous page](https://boards.straightdope.com/t/gps-accuracy-at-the-south-pole-circa-1911-1912/968771.md?page=1)