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Archive 1 |
I see that this article says that Huascaran is not of volcanic origin. Other sources (eg the source on the Santa River and the article which I started on Ranrahirca say that it is an extinct volcano. Can someone find a source that clears up this contradiction. Gerryfarm 08:43, 13 January 2007 (UTC)
Could we get a source on the claim that Huascarán is in a tie with Chimborazo? That isn't in accord with what I have seen. Also, it shouldn't really have to do with determining the geoid. For example, a GPS reading can in principle tell you the distance from the center directly. More practically, a GPS reading measures height relative to a standard reference ellipsoid, and adding in the ellipsoid radius at that location should give the distance from the center. Now, the given heights were not determined by GPS (although they may have since been verified by it?) but they also were not referenced to any complex model of the geoid---the figures are too old for that. They probably also use a spheroidal datum (to the extent that they are accurate at all, which can be an issue for South American peaks). So the claim about the geoid seems spurious and makes the whole claim dubious to me. -- Spireguy 03:05, 14 January 2007 (UTC)
The parameters and formulae are at Earth_radius. I knocked up a basic program:
pi=3.1415926 lat1=9.121389 lat2=1.469167 lat=lat2
p=lat*pi/180 a=6378.135 b=6356.750
t1=a*a*cos(p) r1=t1*t1 t2=b*b*sin(p) r2=t2*t2 t3=a*cos(p) r3=t3*t3 t4=b*sin(p) r4=t4*t4 r5=(r1+r2)/(r3+r4) r=sqr(r5) print r
From this I get a radial difference of 520m between the two latitudes; Chimbo's latitude is further away. According to Wikipedia, the elevations are 6768m and 6267m. But see also the geoid factor, [1]. When extrapolated to sea level, Huascaran's location appears to be c.20m further from the earth's centre than the ellipsoid calculation indicates, in which case it is, indeed, very close.
Elevations of 6746m and 6310m are often given. If either are correct then Chimbo is the winner. I don't believe the latter, but I am not at all sure about the former.
Viewfinder 07:13, 14 January 2007 (UTC)
Thanks to Viewfinder for the numbers. I should clarify what I said earlier about the geoid. It depends on what the reference vertical data for the given elevations are. If the elevations are relative to any standard ellipsoid model, then the geoid is irrelevant. However, if they are relative to mean sea level, then the geoid is relevant, as long as one is using those figures and not, say, a modern GPS reading. Also note that if the two peaks' elevation figures use different ellipsoids, then that throws another wrench into things. Viewfinder, do you know what the vertical data for these given peak heights are likely to be?
Viewfinder correctly points out that even the given figures are pretty widely variable, so even without the issue of the geoid, the uncertainty in these figures make it hard to come to a definite conclusion.
Of course, to put it into perspective, we are talking about a percentage difference of at most 100m/6300km = 0.0016%, so maybe we should call it a tie after all. -- Spireguy 20:14, 14 January 2007 (UTC)
I have no reason not to believe the heights are relative to anything other than sea level. The 6267m for Chimborazo was from a 1993 DGPS survey by Mike Jenkins and is more SRTM compatible than 6310m. Official PIGM 100k mapping has 6746m for Huascaran; I think 6768m is from a more detailed and probably more accurate DAV (German alpine) map. Of course it would be good to get accurate ellipsoidal GPS readings. Any volunteers? Viewfinder 21:00, 14 January 2007 (UTC)
I am puttimg it back. Most of these sources make the claim on the basis that Chimborazo is 6310m, which is too high. Viewfinder 22:15, 23 September 2007 (UTC)
[3] [4] [5] [6] [7] [8] [9] [10] [11] Rracecarr 14:44, 24 September 2007 (UTC)
It was not I; here is the claim. I subsequently checked the calculation at Spireguy's request. Sorry Spireguy, but the words "we should call it a tie" were not mine either. Wikipedia supports 6768m for Huascaran; this seems reasonable, given that it is supported by Austrian Alpine Club mapping that is more detailed and accurate than official Peruvian mapping, although it is possible that 6746m (which would end the debate) is based on a more recent survey. Given this elevation, the above calculation shows that Huascaran is in the running. The calculation is verifiable in that it can be verified by anyone who has studied mathematics to an advanced level; it should therefore be regarded as verifiable fact, not original research. The Chimborazo claim is probably correct, but it has never been proved beyond all doubt. "Reliable sources" frequently make or repeat incorrect claims in the field of topography. Viewfinder 05:54, 24 September 2007 (UTC)
Assuming it is OK to present verifiable information, and a link to the formula that links the information, surely it is then helpful, and not against the spirit if Wikipedia, to apply that formula in a verifiable manner? Are not the OR rules aimed at editors' value judgements, which are not an issue here? Anyway, for now, I amended the " Chimborazo.. is" to "Chimborazo.. is generally regarded as", which is more true and which I hope will be accepted. Meanwhile I will try to find out more about the 6746m vs 6768m elevation (which may settle the matter in Chimbo's favour) or the current thoughts of the so-called "experts" who could provide acceptable sources. Viewfinder 14:14, 24 September 2007 (UTC)
There is no longer a content dispute, and the discussion has moved on to a more general issue and is therefore best not continued here. However, it is an important discussion, so I have moved it to User:Viewfinder/OR. Feel free to contribute to it. Viewfinder 06:59, 26 September 2007 (UTC)
The "source" cited above is clearly copied (not just paraphrased) from an earlier version of Huascarán. This is an illustrative example of what is not supposed to happen with Wikipedia. Wikipedia is not supposed to be an originator of knowledge; it is a tertiary source, and is not itself a reliable primary or secondary source. One should not be able to trace the ultimate provenance of a claim to Wikipedia; that definitely makes it original research. Inserting a claim based on a private calculation is completely out of line with WP policy, for good reason: the claim could be pure fiction or quackery. Firm belief in the truth of the claim by one or even several editors is not enough. As we have recently seen, even a public calculation on the talk page, while certainly more plausible, is not enough.
As to whether this claim, if propagated originally out of Wikipedia, could become "reliable", the answer is simple. If it got checked independently and openly, for example by a calculation published in a peer-reviewed journal, then that would provide a reliable source for the claim. It wouldn't then matter if the inspiration for the claim came from WP, if it was put forth as any other reliable claim would be. I do hope that this claim does not propagate in a way that makes it seem reliable and independently checked, and then gets re-inserted into WP on that basis. Even though I personally believe the claim, if that happens, I'll delete it.
As I mentioned above, I am certainly not blameless in this matter, but as someone who does take contributing to WP seriously, I find the flippant attitude expressed by the "amused" anonymous editor somewhat exasperating. I would suggest that if the anon editor continues to maintain a distinction between "a Wikipedia problem" and "my problem", he/she should not contribute to WP again. -- Spireguy 03:21, 4 October 2007 (UTC)
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