Feet of Climb / Elevation Question

Last night my wife asked me a question about feet of climb I could not adequately answer. So, I thought I would post it here. I have always wondered the same thing actually and have never gotten a “simple” explanation. So, here goes, how is feet of climb calculated? What is the formula, if you will, for calculating it? Is it related to sea level, etc, etc

For example, on day one this year it says we will have 2592 feet of climb. Does that simply mean when we get to Atlantic we will be 2592 feet higher than we were in Council Bluffs? I can’t imagine that is the case.
By the way, my explanation was pretty simple. In 2016 from Glenwood to Creston we had about 4000 feet of climb and that day was brutal for me. In 2017 we had under a 1000 feet from Algona to Clear Lake. That was like coasting. That was my explanation to her, 4000 is really hard and 1000 is really easy.

Anyone have a simple explanation of it?

This topic was modified 9 months, 1 week ago by  Uncle Kraig.

10 Replies

pbot2004, February 3, 2019 at 4:17 pm

It is just the cumulative amount of climbing over the course of the ride. If you ride up 3 30′ rollers that then each drop 30′ your relative elevation hasn’t really changed, but you climbed 90′.

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Barry Schnoor, February 3, 2019 at 4:20 pm

My training route today was a 24 mile round trip. Total net elevation gain was zero…because I started and ended in my driveway. Total climbing was about 1,200 feet because of the all the *little* ups and downs along those 24 miles.

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Uncle Kraig, February 3, 2019 at 4:24 pm

Got it and thanks….it really is that easy then. For some reason, I thought it was a bit more complex but both of your explanations make perfect sense and simple, thanks.

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just randy, February 3, 2019 at 4:41 pm

If you do a google maps search of biking Council Bluffs to Atlantic and select the default route of US-6, it shows a 50.8 mile ride with 2,516 feet of climb and 2,297 feet of decent. Net change is only 218 feet.
On the other hand, if you choose the alternative route through Chautauqua/Weston/Underwood/Neola/Minden/Avoca/Marne the climb over 55.0 miles is only 1,982 feet with 1,762 feet downhill. Net change is 220 feet (rounding difference for us accounting types).
What drives me crazy is when I start and end at home and there is a net altitude gain or loss of 40 feet over 11.8 miles per my GPS. From what I understand, most GPS units use barometric pressure for their calculations and cross wind can impact the reading of climb and decent.

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LawnchairMan, February 3, 2019 at 7:31 pm

Another statistic to consider is feet of climb per mile. You could have a lot of climb one day, but over several miles. Another day could feel “tougher” with less climb if it were several miles shorter. For example, riding 50 miles with 2000 feet of climb should not seem as hard as 1500 feet of climb over 30 miles. The first case was forty feet of climb per mile while the second was fifty. Perhaps I should say the hills would not seem as tough in the first case as in the second. There would still be 20 more miles to do on the first day.
I hope this makes sense.

Another thing to consider is that the Missouri is at a higher altitude than the Mississippi. So we have a net loss as we go West to East. Not sure about that were we to go Southwest to Northeast, but I think it holds true going roughly straight East. Council Bluffs is at 1090 while Keokuk is at 568. 522 feet of loss.

This reply was modified 9 months, 1 week ago by  LawnchairMan.

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MadRanger, February 3, 2019 at 9:10 pm

Heya R-Daryl Daryl and All, FWIW The irony and inaccuracy of your cycling computer showing a net gain or loss in elevation when you do a loop back to your own driveway or any start is due to 3 different amazingly informative but imperfect data sources.

1. The GPS chip in your cycling computer or watch gets its location in 3-dimensional space by collecting signals from at least 4 orbiting GPS satellites. Though it can find your horizontal location with an accuracy most often within 10 feet; the geometry/physics/engineering of calculating vertical position (elevation) is less accurate – and the amount of that error can add up over the course of your ride. (The orbiting GPS satellites ‘see you’ from a lot of different directions – big different angles – in the horizontal plane but only at small angles downwards. Big differences are easier to measure than small differences..)

2. There is also (typically) a tiny digital barometer in your little gizmo that tracks elevation. Both the limitations of its tinyness and atmospheric air pressure changing throughout the ride affects its accuracy. (changing air pressure is how weather happens)

3. Finally when you upload your data into the cloud where your favorite app reads it, the measurements for elevation can be corrected by comparing them to stored databases of elevation maps. These can improve the recorded outcome of the ride – but they’re not perfect either. US Geological survey elevation data may only be within 30′, if other map data is available to your app/service it can be corrected to better accuracy. The elevation maps depend on interpolated elevation data points so if you stand in the ditch next to the road, most likely the map will assume that your at the same height as the road next to you.

Stand up and stretch your arms over your head and your GPS watch ‘thinks’ it gained several feet of elevation. Lay your bike down in the grass and your the cycling computer mounted on your handlebars ‘thinks’ it went downhill about 3 feet. .. GPS science can be entertaining (?) but just biking is the most fun of all! See you in Iowa!

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KenH, February 4, 2019 at 8:50 am

I believe that most bike computers that report climb data are relying on barometric sensors, GPS altitudes being famously undependable and GPS being entirely lacking on some computers that report climb data. Barometric sensors are potentially susceptible to wind noise depending on where their pressure port is located and how you have the unit mounted on your bicycle. Wind sensitivity potentially develops when the wind is from any direction, not just crosswind and the wind produced by your own forward motion can contribute too. However wind induced errors will tend to cancel out because they can be both positive and negative. It is a complex situation however and I would not suppose it to be impossible for wind errors to be relatively consistent in one direction. Even when they do not sum to a net gain or loss over a closed loop course, they could exaggerate the total climb and descent numbers because the climb number just accumulates all the positive excursions and the descent number the negative which excludes the possibility of cancelation.

Barometric pressure changes during the course of your ride will also affect the gain and loss reported when you ride a loop, starting and ending in the same place so that you know the net gain should report as zero. I don’t know how small aircraft operate today but back in the day when you were flying across country it was normal practice to contact the airport you were about to land at to get their barometric pressure reading. You would then dial that reading into an adjustment setting on your altimeter so that you could determine your altitude above ground level more accurately. The same altitude drift happens on bicycle rides of a few hours length unless the barometric pressure is dead steady or even on short rides if the barometric pressure is changing rapidly.

Other things like internal mathematical roundoff errors could accumulate into a net gain or loss in altitude over a loop in some cases. It is also true that the various services you might upload your ride data to could “correct” your elevation data with varying degrees of success but that’s a whole ‘nother can ‘o worms!

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Mark Hotle, February 4, 2019 at 11:07 am

“…cumulative amount of climbing over the course of the ride”

Is correct. But there’s more to the story . The difficulty of the day can depend on the type of hills you’re climbing.
3 30′ hills = the same as one 90′ hill.
Then, you need to factor in the grade of road on the hill.

I’ve done some ‘easy’ rides of 3,000 ft climb and hard 900ft climb rides…

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jwsknk, February 4, 2019 at 12:35 pm

and then there are the number of sample points. the hill might be 30 ft elevation difference from bottom to top, but 20 ft up there could be that little dip of 5 ft you barely notice, thinking that the hill had just leveled out. So now you end up with 35 ft climb on a hill that measured 30 from bottom to top.

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John Richardson, February 5, 2019 at 8:22 am

Ahhh, I thought Iowa was flat. Seriously, wind resistance is by far your biggest challenge. Hills are temporary and are usually followed by a nice coast while a head wind can last all day.

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