Calculating % Grade of a Hill

[Mr. Bloom]

Thanks for the idea! Now, how often do I have to use this GPS in order to make it tax deductible?

That's cool! As for 'tax deductible', forget that...that's just a 'discount'. Get the principal to reimburse the entire thing instead!

I'm convinced that kids respond well to practical learning when enhanced with technology. It's cool that you cared enough to speak to them in 'their language'.

[Chile Pepper]

That's what I thought the calculation was, but then the hill gradients seem really low. A 100% slope would be a 45 degree angle in terms of the hypotenuse of a right triangle. I see people talking about, say, a 10% slope as being difficult, but that would only be 4.5 degrees. I see stuff all the time that looks a lot steeper than that--and I'm not tallking about switchbacks, here. I'm not a spectacular climber, so I'm confused about eyeballing the angle of a slope. Are my eyeball estimates totally off? What would the slope of a hypothetical very-steep-but-climbable section be?

[mimitabby]

yes, 45 degrees is a 100% grade because you are travellling as far forward as you are up.

m not a spectacular climber, so I'm confused about eyeballing the angle of a slope. Are my eyeball estimates totally off? What would the slope of a hypothetical very-steep-but-climbable section be?

I'm really not sure what you consider climbable, but an 8% grade LOOKS formidable
and a 16% grade is tough to walk up and down, and both are climbable by some people.

I don't eyeball them, I have an inclinometer on my bike and my husband has a GPS that's how we figure it out

[Chile Pepper]

Thanks! That little device looks great. I think I'll try it out.

[Zen]

This thread makes my head hurt.

[mimitabby]

ah, come on. Walk 10 feet... now if when you get to the end of the 10 feet you are 2 feet higher than you were in the beginning, that's a 20% grade.

[lacyliz]

I tried calculations- yes, they work. But Specialized, Blackburn and others sell cyclocomputers that give you the %grade of a hill (altimeter feature), feet of elevation, etc. They're fantastic and this way you could compare your hills to hills on other rides, practice the % grade you want and everything. They run about $100, but well worth it (most have cadence, time, mph and everything you could possibly want)

[uforgot]

ah, come on. Walk 10 feet... now if when you get to the end of the 10 feet you are 2 feet higher than you were in the beginning, that's a 20% grade.

Careful! It's not quite as easy as that. If you walk up 10 feet and have risen 2 feet, your horizontal displacement is not 10, it's 9.8, which makes it 20.4%. Not an issue for a small rise, but it certainly is if the rise gets larger! If you walk up a 10 feet slope and rise 5, (30 degrees) it's not 50%, but 57%!

Remember when your Geometry teacher taught you the Pythagorean Theorem and you wondered..."when am I EVER going to use this?" Well, here ya go.