There are lots of hills around my house. Some of them tax me. I am curious if there is a way to measure the % grade. Anybody know a way?
There are lots of hills around my house. Some of them tax me. I am curious if there is a way to measure the % grade. Anybody know a way?
You could always take a 4-foot level & a tape measure and do the math (rise/run = slope). The easier way is to use a "smart level" that has a readout of % grade.
Get a GPS head unit such as a Garmin 500, export the ride data into gpx format, import this gpx into ridewithgps.com and hover over the elevation map on the bottom... this will show you the grade at that point. You can also export the tcx in a spreadsheet and calculate the grade given two points and the change in elevation.
The formula if you don’t have a cycling computer that gives you the grade is:
Elevation gain divided by feet and multiplied by 100.
An 800 foot climb divided by 3 miles would be 800 / 15840= .05050 x 100= 5.050505 or 5.05 percent.
That only gives you a total and in most cases there are places in that climb that will be in excess of 5 percent.
You can sometimes use Google Earth. But the road segment needs to be straight and not tree covered. I have used a grade school protractor, string, and weight to measure ski slopes, but then some segments had a 100 percent slope.
And don't confuse percentage with degrees. It's something along the lines of this: 90° is straight up and has and infinite gradient percentage while 45° has a 100% gradient.
That's gonna leave a mark.
Sometimes you want to measure the slope at various points on a long ride going uphill. That slope will vary between the beginning of the climb to the top of the climb.
Suppose the climb is a total of 1 mile. But you want to measure some spots in between because you have noticed that the climb gets tougher at different points.
To get a general idea without the use of a Garmin GPS type thing, just try Google Earth. There's that ruler icon at the top bar and that will allow you to do the measurement, in feet, meter, anything you want.
If you haven't used Google Earth before, just play with it. Zoom in on that hill climb. Its a click on the mouse to get the elevation changes. The first click sets the starting point so you know the distance in feet.
I slide the cursor and watch the elevation gain go up. If its a quick elevation movement, then I know that its steep.
Last edited by Garfield Cat; 07-04-10 at 06:32 PM.
Most county/city governments will have elevations available for roads. It might take a couple of calls to figure out which dept - surveyor first, GIS, planning , highway etc. Most topographic maps will also have elevations on high points and contour lines to determine elevation for others, scaling the distance and doing the math is nothing. GPS would be easiest.
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Last edited by wahoonc; 07-06-10 at 06:00 AM.
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I noticed you're in Illinois, the grade can't even be measurable! Isn't that why we call you guys flatlanders up here above the cheese curtain?
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On this website http://www.sportdistancecalculator.com/ you can see elevation change and % grade directly on the map by clicking on buton altitude after having draw your route ;-)
Would this work for you?
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Originally Posted by Steely Dan: if you're riding a bike and not having fun, then you're doing it wrong.
An easy way to use a level to measure grades, using a 2 foot level (or double this for a 4 foot level):
Take a stick and mark the grades percentages on it. An 8 inch stick will go up to a 30% grade. 4% grade=.04*24 inches= .96 inches. So mark 4% at slightly under an inch. 6% is 1.44 inches, and so on.
Then set the level's bubble horizontal with one end on the road and hold the stick vertically against one end to see the grade directly, lined up with the bottom edge of the level.
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With experience riding up known grades, you should be able to estimate the grade within a few percent with no tools.
Mapping sites like mapmyride.com and ridewithgps.com use google's elevation data, which can be just an estimate between two known points, so the grades on small sections of roads will often be very inaccurate. For instance, ridewithgps.com shows short grades over 15% on the Blue Ridge Parkway, but the Parkway has no grades over 7%.
But an average grade for the whole hill is usually pretty accurate. I use ridewithgps.com and draw a route up the hill. Use the Terrain View to see where the hill starts and stops on the map. The drawn route shows the elevation at the bottom and top, and the length of the road. So the average grade calculation is easy: 100*(top-bottom in feet)/(distance in miles*5280)
Last edited by rm -rf; 07-06-10 at 08:42 AM.
rm -rf
Quote Originally Posted by xtrajack View Post
Would this work for you?
A bike club rider has one. These handlebar mounted levels don't work on bumpy roads, the bubble doesn't settle in place. If you move your head, the markings aren't lined up correctly with the bubble
This is easier than stopping to get a reading on the inclinometer, how???
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Originally Posted by Steely Dan: if you're riding a bike and not having fun, then you're doing it wrong.
Hmmm.....
I have often wondered and occasionally asked what people mean by % grade. Never gotten a consistent answer from a road engineer though. Here's the problem:
Those quotes above are not consistent with each other, or are at least ambiguous. Does "grade" mean (1) elevation gained per horizontal distance, like the mathematical definition of slope? Or does it mean (2) elevation gained per distance traveled up the slope, essentially the sine of the angle? For small enough slope the two are approximately the same. But with examples like 45deg or 90deg (vertical) the analogies break down.
Definition 2 is more intuitive. By that definition straight up means if you travel X feet total you gain X feet of elevation. It is all up, so the grade might be called 100%. The slope is infinite. You might consider "run" to mean the distance travelled, which makes metabike's formula appropriate.
Definition 1 matches MMACH 5's definition. (One might argue that he defines "gradient", as opposed to "grade", and gradient is not usually specified as %. But we won't quibble, will we?)
If I follow the math of Robert Foster's example correctly (while not bothering with a calculator), I conclude he means definition 2 simply because it uses distance traveled, something measurable with an odometer or computer. By comparison, horizontal distance gained is what we observe on a map, a map being a (necessarily imperfect) horizontal project of the actual ground surface.
It's a minor point for practical purposes, road grades being as small as they are. But I'd sure like to know what a road engineer means by "grade".
Last edited by jimmuller; 07-06-10 at 07:34 PM. Reason: I can't tpye.
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I'd like to know, also. The reason I said "It's something along the lines of..." is because I don't understand it either.
I do remember there being some disagreement about which road holds the title "Steepest Street in the World." And that disagreement arose because one was being reported in percentage while the other in degrees.
That's gonna leave a mark.
Well, I don't carry a level on my rides. I already had the level. And the stick didn't cost $30.
I've used the level and stick twice. Once to measure a very steep local hill. It's actually 18%.
The other time I measured a few spots on a 1 mile climb that google maps showed was near 7 or 8%. I was planning a ride in the Blue Ridge that had long 7% grades and wanted to see how easily I could climb them. The local road was actually 7% too.
Last edited by rm -rf; 07-07-10 at 09:45 AM.
I finally had to good sense to ask my brother who is an architectural engineer. (Duh, why didn't I ask him ages ago?) He wrote back:
10% grade means the vertical rise is 10% of the horizontal run.
Civil engineers (surveyors and site planning) use base 10 scales rather
than feet and inches, so it's easy and natural for them to speak in terms
of percet slope rather than degrees.
This clarifies the term "run" also. So grade is essentially slope. Straight up would be infinite. 45 degrees would be 100%.
Real cyclists use toe clips.
With great bikes comes great responsibility.
jimmuller
Percent grade is 100 times the tangent of the angle...vertical distance divided by horizontal distance. If you use distance traveled along the road rather than horizontal distance, you're using the sine of the angle. For small angles, sine and tangent are approximately equal. Does anyone remember slide rules? They had a scale named SRT for sine, radian, tangent to use for small angles...sine, tangent, and the size of the angle in radians were all close enough to being equal for slide rule accuracy for angles less than 0.1 radian (approximately a 10% grade).
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