DiabloScott

I have literally hundreds of identical rides on Strava up the local 3,800 ft mountain, and the Strava reports all fall within 100 feet of each other. Android app.

I don't trust the % grade callouts on the short sections, but for overall elevation this is probably as precise as any bike altimeter.

indyfabz

Map the dang thing on Ride With GPS. See, e.g.:


https://ridewithgps.com/routes/23254899


Move the cursor along the profile to see grades.

Biker395 

The accuracy of that technique varies. I believe it interpolates between contours of the topo-maps which don't have the resolution required to account for road filling and cutting. I think they have updated their models with other data to improve on that problem, though.

I'm curious what the OP really wants to know.

If it is instantaneous grade, the bubble inclinometers are probably best.

If it is the average grade of a particular climb, computing it from the distanced traveled and the elevation change is best (and if steep, accounting for the sin/tan problem mentioned earlier).

If it is to determine your total climb on a particular day, the best would be to compile different measurements from different devices, account for systematic errors, then compute a statistical average of those devices. Someone involved with double centuries some years ago did just that ... they solicited input from people with different devices to try to best estimate the total climb. It's surprising how much estimates from different devices can vary.

CliffordK

One can also always just take a level and tape measure.

Put one end of the level on the slope, and set it level. Measure straight down to the ground. And, of course, the length of the level.

Divide Rise/Run and express as a percent.

DiabloScott

How much does that bubble jiggle around when you're really climbing though?
Anything over 6% or so and my bike is ... not a good reference frame.

Cyclist0108

I've never used one.

I measure the slope of hills by how much I hyperventilate.

steelbikeguy

It uses a liquid that is more viscous than water, so it doesn't move too badly... but you do need to maintain a steady speed if you want a good measurement.

In the worst case, just check the reading while you are stopped to catch your breath and massage the leg cramps.


Steve in Peoria

Retro Grouch 

That's a fair question. I really had 2 questions. The first was the maximum grade on the 2 mile stretch. The second was the average grade for the entire 2 mile climb. Scott s answered the first question (9%), Jon c. answered the second (4%).


To answer FBinNY's question: Nope, I don't care $20.00 worth, just curious.

CommuteCommando

Not true since the result is "unitless". You could use cubits or angstroms and get the same result.

79pmooney

English - miles to feet: multiply by 5280
Metric - kilometers to meters: multiply by 1000

I rest my case.

(Edit: ignore my previous math. Pre-coffee)

Ben

Biker395 

CommuteCommando

Grade= feet / feet = meters /meters = sticks laid end to end vertically / sticks laid end to end horizontally = x%

Edit, since it may be impractical to lay sticks end to end horizontally, you can lay the end to end up the slope and determine the angle in degrees as arcsin(sleev/sleeUpSlope). O
nce you have this angle the grade is arctan of that.

grayEZrider

I've got these showing 12% from town to home. But the original road going around the highway is far worse. (On short stretches). I think I will take gear and measure on the way to our Thursday afternoon ride with the LBS through Hickory Valley. After failing twice a few months ago, I might even try climbing it again. Maybe.

Trsnrtr

I first posted this long post on measuring % grades. I'm a retired highway engineer.

I try to stay out of these threads because it's more entertaining to just read all the posts.

canklecat

Ditto. Our local modest roller coasters have some short steep sections up to 11%, followed by equivalent downhills, and so on. Those short sections never show quite right on graphs in Cyclemeter, Strava, or any other app or map. But over a mile long segment, or longer, they're accurate enough.

But the apps don't leave us much to brag about. A 10 mile uphill roller coaster slog records as a puny 1% overall climb. Never mind the dozens of short 5%-11% grinds. Makes for great interval training when I have only an hour to ride. But it doesn't look impressive on Strava. On the plus side, I don't need to buy a trainer and find room for it indoors.

kcblair

Yep, I too use the Sky Mount. The bubble stays as steady as I keep the handlebars. KB

DiabloScott

This is my regular ride.

Biker395 

^ Isn't there a really steep pitch at the very end of that climb?

canklecat

We don't have anything like that near Fort Worth. There are some 3-12 mile long grades of 1% overall with some segments up to .4 mile with short stretches of 11%.

Some of the steepest roller coasters are in upscale residential neighborhoods, usually overlooking golf courses. I alternate between those neighborhoods so they don't think I'm casing the joint.

SylvainG

I think what was meant is if elevation is in feet and distance in miles (or fraction of), you need to do that convoluted conversion in that antiquated imperial system.

Cyclist0108

I did it when I was about 25 and in grad school in Berkeley. I should try it again (29 years later).

Machka 

You don't have to lay a bunch of metre sticks end to end. Just use one.


Do I really have to post the how-to photos?

rm -rf

ridewithgps is usually accurate. But they depend on known elevation points, and have to estimate the exact road height in between. This can be occasionally quite wrong on short, steep climbs. And it can be inaccurate locally on roads traversing a steep slope. The average grade, from (top elevation - low elevation) / distance is usually quite accurate.

I've seen a hill with a short 22% pitch in the middle reported as a 13% maximum grade. And a 10% or steeper hill showing as 5%.

One road was rebuilt some years ago, with a deep cut through the steep hilltop, so it now has a steady 6% grade, instead of the 11-12% previously. The satellite view shows the new road, but the Terrain map still has the old elevations.

Strava used to be quite inaccurate on some climbs -- I think they just used the first GPS recording data, and the device can be off calibration. A local bridge approach was reported to start 100 feet under water, for instance.

Measuring with a stick and a level
I actually did this years ago, on a local steep hill. I had a 2 foot level, and marked a stick with 4%, 6%, 8%... markings. So, checking the level, then holding the stick vertical against the downhill side, the grade is shown directly. (Of course, with a meter long metric level, you'd just read the cm marks on a ruler = grade percentage.)

It's interesting how short this vertical stick is! A 10% grade on a 24 inch level means the lower edge is only 2.4 inches off the ground. That seems to be a trivially shallow slope, until you try climbing the road.

fastcarbon

I am not clear why one needs a measurement of grade or elevation with a high degree of precision. I just look at my Garmin readout whenever I care. I would guess the readings are less than + or - 10% in variation. These are not satellite launch parameters.

TimothyH

Rise over run times 100. Done.

Run in miles (or kilometers) may have to be converted to feet (or meters) - Google can do this for you.


-Tim-