Gradients of hills

dan1983
dan1983 Posts: 314
edited July 2008 in The Crudcatcher
Hi guys,

When out riding today my mate and I were wondering what the gradient of the hill we had just ridden up was. Does anyone know how to work this out?

Thanks

Comments

  • Surf-Matt
    Surf-Matt Posts: 5,952
    Find out the horizontal distance (x)
    Find out the change in height (y)

    Divide x by y - this is a gradient.

    e,g, 1000m long (x) and 100m climb (y) - gradient = 1000/100 = 10% or one in ten.
  • Jimbob_no5
    Jimbob_no5 Posts: 1,568
    look on an OS map, they'll be some conversion thing if you google it
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  • Surf-Matt
    Surf-Matt Posts: 5,952
    If anywhere near a road and marked on an OS map:

    one arrow indicates a gradient of 1 in 7 to 1 in 5

    two arrows indicate a gradient of 1 in 5 or steeper
  • dan1983
    dan1983 Posts: 314
    I'll have to see if I can find an OS map. Its one of the trails at Hamsterley Forest though so not near a road.

    Only way I can think of measuring the horizontal distance is to use a bike computer. Thats the only way of getting a reliable measurement that I can think of. Any other suggestions??

    Cheers for the help surf-matt and kona_cowan_rider.
  • ride_whenever
    ride_whenever Posts: 13,279
    use length over height and an os map, you'll be fine.
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  • dan1983
    dan1983 Posts: 314
    The problem is the only OS map of the area I've got is 1:25000 so isn't detailed enough!
  • Surf-Matt
    Surf-Matt Posts: 5,952
    You will struggle to get more detail than 1:25000 from an OS map.
  • dan1983
    dan1983 Posts: 314
    So are there any other ways of doing it? Anything on the net?
  • ride_whenever
    ride_whenever Posts: 13,279
    what scale are the os maps on the interweb?
    Neeermad
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  • dan1983
    dan1983 Posts: 314
    1:25000 on the OS website
  • ride_whenever
    ride_whenever Posts: 13,279
    can you measure the horizontal length on the map and the slope length on your bike and crack out some triginometry?
    Neeermad
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  • Surf-Matt
    Surf-Matt Posts: 5,952
    Where is this fabled hill?
    Someone here might just know!

    My drive is 33% at the top - always a challenge at the end of a run/ride!
  • dan1983
    dan1983 Posts: 314
    Just in hamsterley forest on one of the trails.

    Its nothing too grand, just interested us to find out how steep it is.

    Now I know how to (and finally have a use for GCSE maths - but dont tell my girlfriend, she's a maths teacher and i'm forever telling her how useless it is as a subject and she should teach a proper subject like me), I just need to find the measurements of the hill to work it out!

    Which is proving easier said than done from the comfort of my chair. :roll:
  • nasz
    nasz Posts: 88
    One easy way is to track it with a GPS - then look at the results on a computer
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  • dan1983
    dan1983 Posts: 314
    Easy...if you've got GPS!! :wink:

    Cheers for the idea though!
  • Crispy5449
    Crispy5449 Posts: 73
    Why not post on the trailblazers website - quite a few of the guys on there use GPS when riding in the forest as they are running a vertical climb competition and I'm sure one of them will be able to give you the measurements you need from one of their GPS plots.
  • dan1983
    dan1983 Posts: 314
    Oh right cool, cheers for that I'll give it a go.
  • batch78
    batch78 Posts: 1,320
    map my ride gives a gradient graph at bottom of page, maybe other maping sites too, this'll give distance and height figures, then bit of very basic, dare I say useful!, maths.
  • dan1983
    dan1983 Posts: 314
    Batch, thanks for that, I hadnt noticed it the first time round. I've used it, and I think its right, although according to that the route I plotted is very up-down-up-down whereas in reality its very much just up??

    According to the measurements I've got from there it'll be 14% (659 metres horizontal climb, 47 metres change in height).
  • Surf-Matt
    Surf-Matt Posts: 5,952
    14%?! That's a GAY hill.... :twisted: :lol::lol:
  • dan1983
    dan1983 Posts: 314
    But then I've got measurements from elsewhere that suggest its a 7% hill, so i dont know!! I've given up! My brain has switched off for the summer and wont work!

    Which way round does it work? I'm assuming nearer to 100% = steeper it is? Or am I wrong??
  • supersonic
    supersonic Posts: 82,708
    Gradient % as mentioned earlier is vertical height over horizontal distance (NOT distance travelled, as that is the hypotenuse of the angle, but you can still work it out from here) multiplied by 100. So the higher the percentage the steeper the hill ie 100% works out at 45 degrees slope.

    Also, as the height over horizontal distance is equivalent to the TAN of the angle, you can work out the angle by:

    TAN^-1 H/D

    People often over estimate slopes! Your 14% hill, while steep is just 8 degrees - things do look steeper than we think!

    Another way to do this is to go to google earth and find your hill, take the spot heights and distance and work it out. This will give you the average gradient. Many slopes often have parts that are steeper or shallower than the average, but don't mean much in the grand scheme of things (imagine a bombhole!)
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