Peter Headland <
[email protected]> writes:
>> Others such as the Cateye are optimistic in this regard
> Uh? If I climb 3 feet, I climb 3 feet and I expend energy so to do. Measuring that accurately
> isn't "optimistic", it's a statement of fact.
Oh you don't say. So if I ride from my house to San Jose, both at elevation 60ft and no hills in
between, you want to register the more than 100ft of 0.25% grades along the route as elevation
climbed. That's only the more apparent problem but atmospheric variations usually cause more than
that in pressure fluctuations even though the barometer at the start and finish of such a ride is
also unchanged.
> OK, I grant you there has to be some lower threshold, otherwise we would be measuring every ripple
> in the pavement, but 10m is excessive in my view. The resolution on most of these instruments is
> generally a small (single digit) number of feet (so they don't detect rollers smaller than that),
> and that seems to work tolerably well.
The 10 meter threshold was chosen because it eliminates RR underpasses or overpasses, something most
athletically inclined people take as not a climb, all of it being an optionally anaerobic effort.
For folks who don't ride mountains, this may seem a Draconian theft of accomplishment but these
folks don't need an altimeter anyway. The instrument is designed to give an accurate representation
of climbing over a mountainous route and it does that with greater accuracy than others.
> The real problem is jitter (where the reading is near the boundary between one increment and the
> next and very small undulations or perturbations in air pressure can cause measured elevation
> changes of several feet). Certainly a good algorithm would ignore changes of less than a single
> increment (but perhaps Avocet's dubious patent prevents other makers from so doing - if so, thank
> you Avocet). More annoying still are those instruments that have an over-long sampling interval
> (20 seconds) and perform cumulative calculations based upon those snapshots - you can go down and
> back up quite a long way in 20 seconds.
Are you basically opposed to Intellectual Property (IP) protected by copyright and patents? That is
a discussion subject that is widely discussed in appropriate forums. When I proposed the 10m
threshold in the design, others did not understood why that might be valuable, indicating to me that
the feature should be patented since it was not obvious to others involved in designing the
barometric accumulator. This feature also allows the Vertech wristwatch to count ski runs, an
equally patentable application.
http://www.avocet.com/vertechpages/vertechski.html
> If your complaint is that the accumulated climb is not equal to the difference between the
> elevations at the top and bottom of a climb, I think you are being unrealistic - a climb such as
> our beloved Page Mill road here in the SF peninsula undulates quite a bit, and you certainly have
> to work to regain the losses. FWIW, my Suunto has a "stopwatch" mode that can measure the
> difference between the start elevation and the current elevation, in addition to the accumulated
> elevation change.
I should turn your comment around because insignificant barometric and elevation dithers are not
what most healthy bicyclist wants to record when characterizing a route. In fact, without rejection
software, other instruments record significantly greater elevation gains even on monotonic climbs
with level sections.
> The bottom line is that these instruments are plenty accurate enough for their purpose; expecting
> perfection (even if you can define what that is in this instance) is foolish. The fact that one
> maker's device may give a slightly different result than another's is not significant.
So why are you making a fuss over it?
Jobst Brandt
[email protected] Palo Alto CA
