Measured miles/kilometres in Bristol

Discussion in 'UK and Europe' started by Danny Colyer, Mar 10, 2004.

  1. Danny Colyer

    Danny Colyer Guest

    For years I've thought it would be nice to find a measured
    mile to check the accuracy of my computer against. Then, on
    the way to work this morning, I noticed that the Bath-
    Bristol cyclepath has at least 2 measured and marked
    stretches of 2km and 1 measured mile.

    They're not new. I've seen the markings hundreds of times
    before and have occasionally wondered what they were for.
    The first marking I'd always assumed was something to do
    with a race, the others are all alongside the Bitton railway
    and I assumed they were to do with railway construction. I
    never made the connection between the first marking and the
    later ones.

    Anyway, riding towards Bath from Warmley Station, the first
    marking is just past the Victoria Road crossing. It's a line
    with the word "Start" painted alongside it.

    I didn't notice any further markings until just before
    Bitton station, when I noticed 3 more lines marked '800',
    '900' and '2K'.

    I was overjoyed to think that this was probably an
    accurately measured 2km. Then, just after Bitton Station, I
    noticed another line marked "Start". There are then numbered
    lines every 100m for the next 2km, finishing just before the
    diversion for the new railway construction. And just after
    the 1.6km mark is a line marked '1M'.

    On the way home, I noticed that there are actually markings
    every 100m from where I join the path at Warmley Station to
    Victoria Road. Then more markings every 100m from Victoria
    Road to Bitton Station (with a '1M' mark at 1.62km). I've
    seen them all hundreds of times (I've been commuting this
    way for 4-1/2 years, though the markings may not have been
    there that long) and I never worked out what they were for!

    Anyway, I used them to check my computer this evening.
    Assuming the markings are accurate, my computer was under-
    reading by somewhere between 1% and 2%. I just hope the
    markings are accurate, as I've now corrected the computer to
    agree with them.

    --
    Danny Colyer (the UK company has been laughed out of my reply address)
    http://www.speedy5.freeserve.co.uk/danny/
    Why I like OE6 - http://www.speedy5.freeserve.co.uk/danny/misc/oe6.html
    "He who dares not offend cannot be honest." - Thomas Paine
     
    Tags:


  2. Just Zis Guy

    Just Zis Guy Guest

    On Wed, 10 Mar 2004 22:24:52 -0000, "Danny Colyer"
    <[email protected]> wrote in message
    <[email protected]>:

    >Assuming the markings are accurate, my computer was under-
    >reading by somewhere between 1% and 2%.

    That's pretty good, I'd say.

    --
    Guy
    ===
    May contain traces of irony. Contents liable to settle after posting.
    http://www.chapmancentral.co.uk

    88% of helmet statistics are made up, 65% of them at Washington University
     
  3. On Wed, 10 Mar 2004 22:35:28 +0000, Just zis Guy, you know? wrote:
    > On Wed, 10 Mar 2004 22:24:52 -0000, "Danny Colyer"
    > <[email protected]> wrote in message
    > <[email protected]>:
    >
    >>Assuming the markings are accurate, my computer was under-
    >>reading by somewhere between 1% and 2%.
    >
    > That's pretty good, I'd say.

    Probably as good as you're going to get. My round trip
    commute apparently changes by about 0.2 miles in 19.8 or
    so depending on how hard my tyres are (slick MTB tyres),
    although it's hard to tell exactly how much because it
    varies on a day to day basis by about 0.1 or so anyway.
    I've always assumed that that variation is because I
    take a slightly different line around corners and the
    like each day?

    I guess a road bike with thinner, harder tyres wouldn't see
    that much variation. I run my tyres at 60 but they're
    typically at about 40 by the time I notice enough to
    reinflate them.

    --
    Trevor Barton
     
  4. "Trevor Barton" <[email protected]> wrote in message
    news:[email protected]...

    > Probably as good as you're going to get. My round trip
    > commute apparently changes by about 0.2 miles in 19.8 or
    > so depending on how hard my tyres are.....

    I reckon it's all the wheelies you pull at the lights on
    some days and not others.
     
  5. Andyp

    Andyp Guest

    "Danny Colyer" <[email protected]> wrote

    > For years I've thought it would be nice to find a measured
    > mile to check the accuracy of my computer against. Then,
    > on the way to work this morning, I noticed that the Bath-
    > Bristol cyclepath has at least 2 measured and marked
    > stretches of 2km and 1 measured mile.

    As I think I've probably said on here before I noted the
    location of the mile markers on the Portway for the Bristol
    half marathon. I assume they're capable of doing it
    accurately.
     
  6. Adrian Boliston <[email protected]> wrote:
    > "Trevor Barton" <[email protected]> wrote in message
    > news:[email protected]...
    >
    >> Probably as good as you're going to get. My round trip
    >> commute apparently changes by about 0.2 miles in 19.8 or
    >> so depending on how hard my tyres are.....
    >
    > I reckon it's all the wheelies you pull at the lights on
    > some days and not others.

    If I could pull a wheelie it'd only be because I'd attached
    a large hot air balloon to my gut!

    --
    Trevor Barton
     
  7. "AndyP" <[email protected]> writes:

    >"Danny Colyer" <[email protected]> wrote

    >> For years I've thought it would be nice to find a
    >> measured mile to check the accuracy of my computer
    >> against. Then, on the way to work this morning, I noticed
    >> that the Bath-Bristol cyclepath has at least 2 measured
    >> and marked stretches of 2km and 1 measured mile.

    >As I think I've probably said on here before I noted the
    >location of the mile markers on the Portway for the Bristol
    >half marathon. I assume they're capable of doing it
    >accurately.

    I set my computer by measuring one wheel-rev on bicycle
    wheel at typical inflation under typical load. I think I
    can do that to better than 1%. I've found that to agree
    over several miles within 2% with what a handlebar-mounted
    GPSR gives.

    Consider the difference between a new tyre, and one worn
    down to replacement level.

    I have my doubts about mile markers. In my youth I wasn't
    easily able to measure a mile accurately, but I was able to
    notice that different alleged measured miles were different
    lengths by several per cent.

    --
    Chris Malcolm [email protected] +44 (0)131 651 3445 DoD #205
    IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
    [http://www.dai.ed.ac.uk/homes/cam/]
     
  8. Danny Colyer

    Danny Colyer Guest

    Trevor Barton wrote:
    > I guess a road bike with thinner, harder tyres wouldn't
    > see that much variation. I run my tyres at 60 but they're
    > typically at about 40 by the time I notice enough to
    > reinflate them.

    You're right, I really ought to measure the effects of
    varying tyre pressure. I usually run mine at 100psi, but
    when I come to top them up I sometimes find they've dropped
    as low as 60psi (more often about 80psi).

    --
    Danny Colyer (the UK company has been laughed out of my reply address)
    http://www.speedy5.freeserve.co.uk/danny/
    Why I like OE6 - http://www.speedy5.freeserve.co.uk/danny/misc/oe6.html
    "He who dares not offend cannot be honest." - Thomas Paine
     
  9. Danny Colyer

    Danny Colyer Guest

    Chris Malcolm wrote:
    > I set my computer by measuring one wheel-rev on bicycle
    > wheel at typical inflation under typical load. I think I
    > can do that to better than 1%.

    I used to think that, when I used to ride a bike with the
    computer magnet on a 26" wheel. I'm not so satisfied with
    the measurements on a 20".

    I do two wheel revs at typical inflation under typical load
    (5 measurements, discard the highest and lowest readings,
    take the mean of the remaining 3), but I'm conscious that I
    might not ride quite as straight at low speeds on my patio
    as in real life. I'm also concerned that the unevenness of
    my patio paving slabs might make a difference. I really
    ought to do my rollouts somewhere else...

    Oh, and because I do the rollout largely with my feet on the
    ground, rather than on the pedals (at the front of the
    bike), the weight distribution on the front wheel (where the
    magnet is) will be slightly different.

    > I've found that to agree over several miles within 2%
    > with what a handlebar-mounted GPSR gives.

    It would be nice to try GPS.

    > I have my doubts about mile markers. In my youth I wasn't
    > easily able to measure a mile accurately, but I was able
    > to notice that different alleged measured miles were
    > different lengths by several per cent.

    I've tried other mile markers and found their spacing to be
    inconsistent. The great thing here is that I've found 3 sets
    of markings which are completely consistent. Probably all
    measured using the same wheel, of course, but the
    consistency is a good sign.

    --
    Danny Colyer (the UK company has been laughed out of my reply address)
    http://www.speedy5.freeserve.co.uk/danny/
    Why I like OE6 - http://www.speedy5.freeserve.co.uk/danny/misc/oe6.html
    "He who dares not offend cannot be honest." - Thomas Paine
     
  10. Tom

    Tom Guest

    "AndyP" <[email protected]> wrote in message news:<[email protected]>...

    > As I think I've probably said on here before I noted the
    > location of the mile markers on the Portway for the
    > Bristol half marathon. I assume they're capable of doing
    > it accurately.

    The total course measurement for the half will be super-
    accurate, but intermediate miles may be much less so (often
    depends on where there is a lamp-post to hang a marker).

    Tom
     
  11. On Thu, 11 Mar 2004 23:09:53 -0000, in
    <[email protected]>, "Danny Colyer"
    <[email protected]> wrote:

    >the remaining 3), but I'm conscious that I might not ride
    >quite as straight at low speeds on my patio as in real
    >life. I'm also concerned

    Thinking about it, since the front wheel has more lateral
    wobble then a rear wheel sensor would actually be more
    accurate in terms of forward distance travelled.

    --
    DISCLAIMER: My email box is private property.Email which
    appears in my inbox is mine to do what I like with. Anything
    which is sent to me (whether intended or not) may, if I so
    desire, form a legal and binding contract.
     
  12. On Thu, 11 Mar 2004 23:09:53 -0000, in
    <[email protected]>, "Danny Colyer"
    <[email protected]> wrote:

    >the remaining 3), but I'm conscious that I might not ride
    >quite as straight at low speeds on my patio as in real
    >life. I'm also concerned

    Thinking about it, since the front wheel has more lateral
    wobble then a rear wheel sensor would actually be more
    accurate in terms of forward distance travelled.

    --
    DISCLAIMER: My email box is private property.Email which
    appears in my inbox is mine to do what I like with. Anything
    which is sent to me (whether intended or not) may, if I so
    desire, form a legal and binding contract.
     
  13. Danny Colyer

    Danny Colyer Guest

    Richard Bates wrote:
    > Thinking about it, since the front wheel has more lateral
    > wobble then a rear wheel sensor would actually be more
    > accurate in terms of forward distance travelled.

    I think my rear wheel currently has quite a bit more lateral
    wobble. But that should change tomorrow when I fit the new
    one that I built last weekend. I really should have got a
    new hub a couple of months ago.

    I'd like to use a rear wheel sensor, but with both the
    computer and the cadence sensor having to be mounted to the
    derailleur tube at the front of the bike I doubt I'd find
    anything with wires long enough to reach.

    --
    Danny Colyer (the UK company has been laughed out of my reply address)
    http://www.speedy5.freeserve.co.uk/danny/
    Why I like OE6 - http://www.speedy5.freeserve.co.uk/danny/misc/oe6.html
    "He who dares not offend cannot be honest." - Thomas Paine
     
  14. Andy Dingley

    Andy Dingley Guest

    On Wed, 10 Mar 2004 22:24:52 -0000, "Danny Colyer"
    <[email protected]> wrote:

    >I noticed that the Bath-Bristol cyclepath has at least 2
    >measured and marked stretches of 2km and 1 measured mile.

    Talking of the Bristol-Bath path, did anyone else nearly run
    into that fallen tree a few weeks back ? Damned council
    felled it one day and then left it lying there at head
    height overnight, no markers, lights or anything !

    I can _almost_ forgive them for carving the faces into the
    two remaining stumps.

    I work in Bath these days and commute from Fishponds.
    Black MTB, black h*lm*t, yellow courier bag. Say hi if
    you see me !

    --
    Smert' spamionam
     
  15. Danny Colyer

    Danny Colyer Guest

    Andy Dingley wrote:
    > Talking of the Bristol-Bath path, did anyone else nearly
    > run into that fallen tree a few weeks back ? Damned
    > council felled it one day and then left it lying there at
    > head height overnight, no markers, lights or anything !

    Which one?

    There was one near Saltford that blew over during a blizzard
    a couple of weeks ago. You probably don't mean that one.

    There was one that blew over on a Saturday night just North
    of Victoria Road. They removed that on the Sunday.

    There was another one that came down a few days later in the
    same place. A friend spoke to the council workers who
    removed it, apparently it was cut down by some yob for a
    laugh, not by the council.

    I can't think of any other recent ones between Warmley and
    Saltford (the stretch I commute along). South
    Gloucestershire and B&NES councils are both usually pretty
    good at removing fallen trees, IME.

    > I can _almost_ forgive them for carving the faces into the
    > two remaining stumps.

    I haven't noticed that. I reckon you probably mean the ones
    by Victoria Road, I'll have a look tomorrow.

    > I work in Bath these days and commute from Fishponds.
    > Black MTB, black h*lm*t, yellow courier bag. Say hi if you
    > see me !

    I'll keep an eye out, although we're both travelling in the
    same direction so I probably wouldn't see you too often. Red
    Street Machine recumbent, BTW.

    --
    Danny Colyer (the UK company has been laughed out of my reply address)
    http://www.speedy5.freeserve.co.uk/danny/
    Why I like OE6 - http://www.speedy5.freeserve.co.uk/danny/misc/oe6.html
    "He who dares not offend cannot be honest." - Thomas Paine
     
  16. Danny Colyer

    Danny Colyer Guest

    Andy Dingley wrote:
    > > I can _almost_ forgive them for carving the faces into
    > > the two remaining stumps.

    and I responded:
    > I haven't noticed that. I reckon you probably mean the
    > ones by Victoria Road, I'll have a look tomorrow.

    I looked. I *like* the faces.

    I took some pictures with the camera that I keep in my
    bumbag: http://www.speedy5.freeserve.co.uk/z-faces01.jpg http://www.speedy5.freeserve.co.uk/z-
    faces02.jpg

    I shall have to go along there some time with a decent
    camera.

    --
    Danny Colyer (the UK company has been laughed out of my reply address)
    http://www.speedy5.freeserve.co.uk/danny/
    Why I like OE6 - http://www.speedy5.freeserve.co.uk/danny/misc/oe6.html
    "He who dares not offend cannot be honest." - Thomas Paine
     
  17. Frobnitz

    Frobnitz Guest

  18. Danny Colyer

    Danny Colyer Guest

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