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# how do you measure hill grade?

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Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

# how do you measure hill grade?

04-21-09, 01:51 PM
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how do you measure hill grade?

is this done mainly by gps computation now-a-days? i often read or hear people talking about hills they climbed and refer to their steepness by grade %.

of course i understand mathematically how to determine a hills angle, but without a trusty protractor is there some method of estimating grade?
04-21-09, 01:53 PM
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Originally Posted by AngryScientist
is this done mainly by gps computation now-a-days? i often read or hear people talking about hills they climbed and refer to their steepness by grade %.

of course i understand mathematically how to determine a hills angle, but without a trusty protractor is there some method of estimating grade?
https://en.wikipedia.org/wiki/Slope

Have fun:
https://www.toporoute.com/cgi-bin/bicycle.cgi
04-21-09, 01:54 PM
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mapmyride.com
04-21-09, 01:59 PM
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rise/run * 100 = % grade

(although it should be noted that a bike computer measures the wrong "run", e.g. the hypoteneuse of the right triangle, not its base)

but it's close enough.
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04-21-09, 01:59 PM
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Originally Posted by AngryScientist
is this done mainly by gps computation now-a-days? i often read or hear people talking about hills they climbed and refer to their steepness by grade %.

At the foundation of all these estimates and calculations are measurements made by surveyors and maps made by cartographers.
04-21-09, 02:01 PM
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04-21-09, 02:09 PM
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Originally Posted by mattm
rise/run * 100 = % grade

(although it should be noted that a bike computer measures the wrong "run", e.g. the hypoteneuse of the right triangle, not its base)

but it's close enough.
If you are using a Garmin w/GPS instead of wheel sensor it is measuring the base not the hypotenuse. Not that it matters much for the shallow angles we are talking about.
04-21-09, 03:08 PM
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This is great stuff...love the mapmyride...I too have been curious about grades on various roads...I'll measure a few and then should be able to estimate others...nice, thanks!
04-21-09, 03:10 PM
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Originally Posted by Jive Turkey
mapmyride.com
Extremely inaccurate.
04-21-09, 03:11 PM
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Originally Posted by AngryScientist
is this done mainly by gps computation now-a-days?
GPS is not very accurate for elevation. A barometric altimeter is better.
04-21-09, 03:22 PM
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oh my...mapmyride is too much fun!!!
04-21-09, 03:33 PM
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Originally Posted by johnny99
Extremely inaccurate.
One thing that I have noticed is that gradients which appear in a localized short segment, do not necessarily appear when I expand the route....for example: when I look at a small street near me, I see a gradient of up to 19% (let's assume this is reasonably accurate for the moment -- it is steep)...but, when I extend the route -- including this segment -- suddenly the gradient range does not include anything near 19%!! Now, I just started playing with this, so, perhaps I am misreading something in the table...
04-21-09, 04:41 PM
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i typically hire surveyors for all the hills i ride.
Once they are done, my training schedule can be perfected.
04-21-09, 05:14 PM
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don't try this at home.

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One of the local riders used a mapping database to calculate accurate grades on a list of local hills. After checking the list and riding some of those hills, I can usually estimate a grade within a few percent for the typical 2%, 4%, 6%, 8% grades now.

Mapmyride uses the google elevations which are estimated between known points. If you look at Google Earth in 3-D, you often see lakes tilted down the (estimated) sides of hills. And the elevation graph averages out the grades. On a 40 mile route, a half mile 10% grade might show as an average 4% over 2 miles.

If you want to get a more accurate grade, you can try the topo view in mapmyride, get the elevation from the contour lines, and draw a short route up the hill to get the distance. Then just calculate 100 * elevation / (mileage*5280)

To get a rough idea of grades, use the Terrain View in mapmyride or google maps, zoomed in all the way. It shows contour lines at 40 foot intervals, with a heavy line every 200 feet. You can get a good feel for steepness by comparing the interval distances with a hill you already know.

Last edited by rm -rf; 04-21-09 at 05:17 PM.
04-21-09, 05:17 PM
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In my experience, the grades on mapmyride are reasonable but any cumulative ascent figures over a route are not.
04-21-09, 05:24 PM
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My Garmin 305 tells me the grade. I usually get about a C+.
04-21-09, 05:46 PM
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Originally Posted by AngryScientist
is this done mainly by gps computation now-a-days? i often read or hear people talking about hills they climbed and refer to their steepness by grade %.

of course i understand mathematically how to determine a hills angle, but without a trusty protractor is there some method of estimating grade?
Sure. Just add a couple percent to whatever the last guy said he rode.

However, a barometric altimeter is also a good and cost effective way to go. My wired VDO MC 1.0 has been decent.
04-21-09, 08:21 PM
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What most of us do here is claim a 10% increase from the last person to post as in my fastest climb happened on a X% grade. Seems to work well. It is far from being correct but it is fun.

Last edited by John1992; 04-21-09 at 08:58 PM.

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