Talk:Huascarán

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[edit] Contradiction with other sources on Wikipedia

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)

The source is already included on this page; it clearly states that the peak (and the entire range) is non-volcanic. The idea that Huascarán is a volcano is, as far as I can tell, pure legend, possibly due to a confusion between the massive earthquake-induced landslides that have occured on the peak and volcanic eruptions. When I edited this article to remove the false claim that it is a volcano, I looked around the internet quite a bit, and indeed one does see mention of it as an extinct volcano. However none of these internet pages had a source or any justification of the claim. Also, Huascarán does not show up on any reputable volcano site. So I see no reason to doubt my printed source, the one currently referenced.

I'll go ahead and change the other two articles that you mention. Let me know if there are any more places on Wikipedia with this false claim. -- Spireguy 02:46, 14 January 2007 (UTC)

[edit] Farthest from Earth's center

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)