Slope Angle on Non-Snow Terrain

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ezabielski
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Re: Slope Angle on Non-Snow Terrain

Post by ezabielski »

letitbeirie wrote: Sun May 23, 2021 12:14 pm
Robbie Crouse wrote: Fri May 21, 2021 12:24 pm On the Keyhole route, I just checked the Homestretch and on caltopo at least it averages 48 degrees with a max of 57 degrees. That seems pretty consistent with the other class 3 angles. On the Narrows, you're right that you are traversing, but it's 54 degrees on the steepest part around it.
Wow it's really that steep? I think freeway on the second flatiron averages about 48 too, but it's class 4 or low 5, depending on who you ask.
I just measured the meaty part of the homestretch and a straightline version of Freeway and they are both within 1 degree at about 46 degrees. Kind of a pointless exercise though, since nobody takes a perfectly straight line on either. Add in a few real life wiggles and they are both less than 40 degrees on average. Max angle is pointless. Freeway is more than twice as long as the Homestretch, and definitely has harder parts than the Homestretch. But I think the middle section of Freeway is really similar to steepness and climbing on the Homestretch, not more than class 3. You can go up and down both quite fast if you practice.
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Re: Slope Angle on Non-Snow Terrain

Post by Robbie Crouse »

Here's Caltopo on it:

Longs caltopo.JPG
Longs caltopo.JPG (160.23 KiB) Viewed 1910 times
Longs caltopo 2.JPG
Longs caltopo 2.JPG (18.42 KiB) Viewed 1910 times
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Re: Slope Angle on Non-Snow Terrain

Post by Robbie Crouse »

I'm not sure how accurate Caltopo is. Sometimes it seems to exaggerate the steepness; other times it seems wildly under.
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Re: Slope Angle on Non-Snow Terrain

Post by justiner »

Robbie Crouse wrote: Sun May 23, 2021 10:00 pm I'm not sure how accurate Caltopo is. Sometimes it seems to exaggerate the steepness; other times it seems wildly under.
It's as good as the DEM data it's pulling from, which is usually pretty OK. But the actual terrain it's modeling can vary wildly. Also be very very careful of the sampling interval. The sampling interval for Homestretch is only every 45'. Not bad, but Homestretch isn't all that long - the slope profile you're going to be shown is very much averaged/normalized out. I wrote about this!

https://justinsimoni.com/2021/05/12/got ... gain-loss/

But the slope angle of Homestretch is quite regular - it's just about as steep on the bottom of Homestretch as it is on top - there's no like: 10' wall in the middle that would be hidden by the slope angle profile chart Caltopo is generating.
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Re: Slope Angle on Non-Snow Terrain

Post by Robbie Crouse »

That's really interesting, Justin. Thanks for writing that up. I didn't know about the sample size / resampling issue on Caltopo. (For what it's worth, it didn't really make a different on the Homestretch, but as you said, it's a small sample size anyway).
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Re: Slope Angle on Non-Snow Terrain

Post by Jorts »

Dave B wrote: Thu May 20, 2021 9:08 pm Knife edge on Capitol is pretty much flat and is 3-4th class.
Is it really 3-4th class though? I think exposure and climbing difficulty get conflated. Narrow catwalks are often class 1 or 2 but most hikers are reduced to butt shimmying because of the extreme exposure.
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Re: Slope Angle on Non-Snow Terrain

Post by Dave B »

Jorts wrote: Mon May 24, 2021 8:02 am
Dave B wrote: Thu May 20, 2021 9:08 pm Knife edge on Capitol is pretty much flat and is 3-4th class.
Is it really 3-4th class though? I think exposure and climbing difficulty get conflated. Narrow catwalks are often class 1 or 2 but most hikers are reduced to butt shimmying because of the extreme exposure.
Definitely a gray area where exposure and difficulty intersect. Given the almost certain death in a fall, then I'd say, yes, it's definitely 3rd or 4th class.

If a hypothetical route existed where the only challenge was an exact replica of the knife edge, but everything else was C1 trail, I'd be pretty surprised if anyone called the route class 1 or 2.
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Re: Slope Angle on Non-Snow Terrain

Post by SamWerner »

Jorts wrote: Mon May 24, 2021 8:02 am
Dave B wrote: Thu May 20, 2021 9:08 pm Knife edge on Capitol is pretty much flat and is 3-4th class.
Is it really 3-4th class though? I think exposure and climbing difficulty get conflated. Narrow catwalks are often class 1 or 2 but most hikers are reduced to butt shimmying because of the extreme exposure.
I'd be really curious to see an exact replica of the Kelso or Capitol knife edges, but at ground level to reduce the exposure/mental aspect of it. I'm not doubting your assumption, I'm just having trouble separating the different aspects in my head.
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Re: Slope Angle on Non-Snow Terrain

Post by jibler »

Angle-a Merkel'd
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Re: Slope Angle on Non-Snow Terrain

Post by Robbie Crouse »

I think the best way to think about "class" is "difficulty," both mental and physical. Exposure causes mental difficulty so that one's mental energy has to be laser focused, and that has an effect on physical difficult. But exposure alone can't really make the class change either. A catwalk that is basically a sidewalk in the sky isn't physically difficult, but you have to be more alert. A knife-edge isn't a catwalk since you do need to use your hands in some fashion -- or do the butt-scoot. It has both some physical difficulty combined with mental pressure.
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Re: Slope Angle on Non-Snow Terrain

Post by Jorts »

Doesn't necessarily look 4th class here. But ratings are subjective right?
Andrew Hamilton's son on Capitol's knife edge
Andrew Hamilton's son on Capitol's knife edge
Andrews-son-Axel-on-Capitol-Peaks-Knife-Edge-at-age-6-in-2013-Andrew-Hamilton.jpeg (34.34 KiB) Viewed 1602 times
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