RE: [prominence] Re-post of BC spire Top 50
- [Mike Cleven:]
Just glanced at the list to see what was on it.
Frankly, I still haven't sat down and worked out how
you calculate spire measure, but I'm curious as to why
Mt Currie is on the list and nearby Wedge isn't (Wedge
is higher, and has at least a steep a face, I think);
there's not a big col between the two (341m only for
Currie); maybe it's because you use the 4 compass
points to calculate spire measure, and the ridge the
col is on is SE?
Thanks Mike for mentioning this one---this is a good example of how spire measure works and how it often ranks a lower, but steeper, peak higher. (That is exactly what it is designed to do.) The spire measure of Mt. Currie is 547m; that of Wedge is 454m, quite a bit lower, even though Wedge is about 400m higher. Let's see why.
One good way to get a rough idea of the spire measure of a peak is to look at the drops to the nearby valleys. For Mt Currie (the North Peak, which is the one which gets the best spire measure), the North face drops an impressive 2260m in 3.5km. (See e.g. the picture on the Mt. Currie page at bivouac.com.) (We can also compare this 7415ft drop in 2.15mi to Fred Beckey's famous criterion of 6000ft in 3mi---wow!) Wedge Mountain, on the other hand, while higher, is much more set inside the high part of the range, and so it doesn't have that kind of big steep drop. The best it does in 3.5km is about 1700m, from what I can tell on BC Basemap. (No slouch, but not as good as Mt Currie.) It seems to just miss the Beckey criterion.
Now, spire measure doesn't just take the aforementioned drops into account, nor does it just do the cardinal directions as Mike suggests; spire measure takes into account all of the drops at all distances in all directions and takes a certain average. However looking at these "best" drops usually gives a good idea of why one peak beats another. Currie simply has bigger steep relief than Wedge. Based on height or prominence considerations, Wedge beats Mt. Currie; based on local relief and steepness, Mt. Currie beats Wedge. The latter is what spire is designed to measure.
(I'll also note that the col between the two peaks is irrelevant to spire measure, though it is of course crucial to prominence. That is another point that it is good to clarify; spire measure is a very different kind of metric from prominence.)
Aaron Maizlish has been helping out checking various
entries in the Bivouac database; not sure if any of
this affects your data but have a look at 2445m Peak
33-58 Kalahin http://bivouac.com/MtnPg.asp?MtnId=7360
which got revised upwards today to 1640m from 1525m
prominence thanks to his topo-hunting; reason I'm
commenting is that the "new" col is much closer to the
peak in question. I THINK that affects spire measure;
but again I'm going to have to study the math....
As I mentioned above, the cols and prom values are irrelevant, but thanks for noting the change. Also, I checked the peaks on this list directly against the basemap, partly since some of the peaks are not on the bivouac database. This is in some measure for the same reason as in the Currie/Wedge example above: bivouac focuses on high-elevation and high-prom peaks, and some of the best peaks by spire measure are not particularly high-elevation or high-prom (by local standards). So while bivouac was very useful for identification and context, the actual spire numbers shouldn't be influenced by any inaccuracies in the bivouac data.
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- Mike---thanks for the additional comment/question. I hope this is still of some interest to others on the list. If the discussion gets very technical I'll start replying personally.
I noted "Mount Douglas" at the bottom end of the list,
and again leaves me scratching my head as to how Spire
Measure works; this is one of the lower summits around
these parts, and there's others that (to me) seem far
steeper/higher. I gather, again, that it's because
Spire Measure works off the four compass points,
instead off of absolute geometry? i.e.
As I mentioned in the other reply, spire measure is omnidirectional, and doesn't just focus on compass points. Douglas comes up quite well primarily because of that steep SW face which, as you mention below, shows off very well in the pictures. (A good clue that it will have a good spire measure!) In particular it drops about 1940m in about 2.64km (this is the drop of the optimal point for spire measure, not the summit), which is very good. That kind of high, steep drop is what spire measure rewards. You can compare to the Wedge number I gave in the other email, namely 1700m in 3.5km, not so impressive. The extremely low base provided by Harrison Lake is crucial to how a low peak like Douglas can get a high spire measure. Peaks like this, in a way, are the most interesting ones for spire to pick out, since they will not show up on a list by elevation. Saying Mt. Waddington is impressive is not news; noting that this peak is impressive for its small (absolute) stature is interesting.
Another important note about the list: since the ranking is by reduced spire measure, which demotes peaks which are nearby better ones (according to spire measure), some of the peaks you are thinking of as higher/steeper might not be on the list for that reason. (E.g. a lot of the peaks right next to Waddington.) If you have a particular peak you want to know the spire measure of for comparison, let me know, it's easy for me to get a figure on it if I don't have it already.
BTW this was unnamed officially at some point; it was
in the official lists as Mount Douglas but taken off
at some point, for undeterminted reasons; the only
official Mt Douglas in BC is a tourbus-plagued bump in
northeastern Victoria. Can't see why this one was
"unnamed"; the townsite of Douglas at the north end of
Harrison Lake was the oldest non-native settlement on
the mainland, and the name Douglas is of course deeply
associated with that period of BC history. it's quite
a striking looking thing, too, for all of its 2076m:
Thanks for the note about the name; I'll keep referring to it as Mt Douglas, since bivouac still is using that name.
Thanks for the interest,
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> * Mount Bute exemplifies a lot of the peaks on this list: it liesThis is not unusual. When I went to Europe several years ago, the flight
> next to tidewater (at the head of Bute Inlet) and on the edge of
> one of the major icefields (the Homathko).
> (By contrast, some of the highest peaks in the Coast Range
> do not show up on this list since they lie in the interior of
> these icefields, away from low, steep terrain.)
from Minneapolis to Oslo went over Greenland. The coast was rugged and
fjorded with tidewater glaciers everywhere. The interior was a vast, smooth,
ice sheet with almost no relief at all. I would guess that most of
Antarctica, and some parts of the Saint Elias, are also this way.
Edward "7.389056099" Earl
"As I hiked along the trail, I saw a flicker of tail and a lizard
disappeared down a hole into an underground tunnel. The lizard then came
face-to-face with the mouse that lived in the tunnel."
>[Edward:]This is definitely true for Antarctica: the best spire measures there
>This is not unusual. When I went to Europe several years ago, the
>flight from Minneapolis to Oslo went over Greenland. The coast was
>rugged and fjorded with tidewater glaciers everywhere. The
>interior was a vast, smooth, ice sheet with almost no relief at
>all. I would guess that most of Antarctica, and some parts of the
>Saint Elias, are also this way.
will generally be found on the coasts, with some exceptions like the
spires of Queen Maud Land. However the Saint Elias is different; the
best spire measures there are the biggest mountains, not smaller peaks
on fjords. The Saint Elias isn't as much of a plateau/fjord system as
Greenland, Antarctica, or the Coast Range.