First it can be blocked from receiving a signal, during this time it
goes blind and has no idea where you are. Trees buildings etc can block the
Second is the sampling rate. It measures then computes the distance
from the last time it measured. Some units don't measure too often. I hope
the new Timex unit has a rapid sample time reducing this problem. It is a
problem because runners don't generally run only straight paths, and bend or
turn of your path between samples will be replace by a straight line in the
mind of the GPS.
I do have a GPS unit and I can say from personal experience they are
good for many things, even better now that the US government has turned off
it's intentional errors. Over long straight distances they are very
accurate and they are very good at finding specific locations from a map.
My girlfriend is into genealogy and we often are trying to find some old
grave location in the middle of some farmer's field. The GPS takes us right
there, or close enough. But I also know they can have problems finding and
keeping contract with the satellite and a curvy path will be under recorded.
Joseph E. Meehan
26 + 6 = 1 It's Irish Math
> I've had my eye on the Fitsense or Nike for months, but I've held out
> for various reasons. One of the reasons is I really don't have a
> reliable place to calibrate them and I'm too lazy to go find a track
> where I can do so :).
David (in Hamilton, Ont)
"This body holding me reminds me of my own mortality
Embrace this moment; remember, we are eternal
All this pain is an illusion."
Tool - Parabola
> > You an calibrate the FitSense on ANY length measured course you can find
> ...that was originally measured with what? ;-)
> > or on a treadmill.
> Using a treadmill to calibrate another device? I'm assuming
> you don't run on treadmills too often, as they are not very
> accurate, not enough for calibration purposes, anyway!
Actually, the real accurate numbers for me were somewhere between
the track calibration and the treadmill. I used the "calibration"
page on the website to refine the setting and it came up spot on
on the last 20 mile long run.
There are some excellent threads, quite recent in fact, on comparisons
between the two foot pod systems, both are based on the same technology
and when properly trained seem to give a 98 % or better accuracy. I
bought the Nike because of the training system, you run a known metric
course and then adjust for accuracy. Since 400 meters is only 7 feet shy
of a quater mile you can adjust any track or known course to accomodate,
because the Nike will allow you to use any distance to calibrate. The
Fitsense calls for either 400 meters or a timed treadmill training, but
does allow for manual adjustments later on, which the Nike does not.
I also bought the Nike because I belong to the run club at road runners
sports and they have a 60 day no questions asked return policy, but they
ain't getting this baby back, its just too much fun to make your own
course and still have all that ***retentive data. RRS now carries the
Fitsense as well. the Nike system is similar to their other watches and
I've been using the Triax's for over 3 years so the learning curve was
less. A lot of people don't like the Fitsense because of the styling of
the watch, which is way different but those who have them seem to like
Bottom line either one should be more accurate than the Timex, until
proven otherwise, and either will be way more more useful to a training
program than a HRM.
It really depends on your desire for complete accuracy. If you
want you could go drive a mile with your car and calibrate. The unit
will simply say the same distance as your car, which by the way isn't
A question I would like to know about the GPS unit is how
accurate are they? It was my impression that GPS's were only accurate
within 10-20ft. If your running at 7MPH or roughly 8:30 you are moving
at 10.26 ft/sec. If the unit updates pace every 5 sec, rough what the
Triax does, you would cover about 51.3 ft Even if the GPS is within 5
ft thats about 10% error. I at any given time or it would report you
were running from a 7:39 to a 9:21. Wondering how the GPS actually
calculates pace? The good thing I can see about GPS is it would never
be off more than the error of the GPS. If you run 50ft you may be 5 ft
off. However if you run 50 miles you will only be 5 ft off. Not true
with the other foot units, there error is cumulative. The foot units
are also susceptable to running error's I.E. tripping, changing of
gate etc. GPS would not be.
David (in Hamilton, Ont)
"These roads go on forever, and so do you and I"
Every time I see a thread on one of these devices, I want one. They
sound like a lot of fun to play with, especially when you are just
going out for a couple hour run. One of these days, I'm going to
break down and shell out the money. If they were $100 or less, I'd
probably get one today.
1. I don't have any trouble paying $100+ for a pair of shoes that wears
out in less than a year, so an investment of $200 in a device that will
last several years seems okay.
2. Compared to a lot of other sports and outdoor activities, $200 is a
bargain. We're way ahead of golfers, skiers, bicyclists, and especially
boaters. You save so much by being a runner, you owe it to yourself,
3. I used to work as a musician, and currently work as a computer geek.
In either endeavor, $200 for a cool gadget is no biggie. Why should
running be any different?
Bottom line: We're used to this sport being inexpensive, so it's a little
tough to swallow a $200 price tag on anything. But, in the grand scheme
of things, it's not really all that expensive.
At least, that's what I keep telling myself. :)
All good points, and I love gadgets. If I can just make it a little
longer with no new gadgets, then this will probably be my next
purchase. The problem is, it shouldn't matter to me how far I
actually ran on my long run, as long as it's for a certain amount of
time. Plus, I already have a pretty good idea how far I've gone.
Right now, I'm not doing any interval work, but if I started, that
would be a good reason to get one. I watch eBay now and then for one
of these, but there are no bargains there. I just checked, and there
is on Nike SDM Triax, and it's already up to $180. At that price, you
may as well buy straight from Nike and make sure you have a valid
I am sort of going through mid-life simplification process. Tired of
getting more 'stuff' all the time. For example, we moved up north
last summer and my wife said I should go buy a snow blower and I just
said that I would shovel. (A mild winter made my decision seem pretty
smart.) I guess it's kind of strange, but better than the typical
mid-life crisis of buying a new sports car and running off with a
"San Francisco isn't what it used to be, and it never was." -- Herb Caen
thread, I wear progressive lenses and can read the main display without
glasses but the fine print is probabmatic while on the run because of
the dot matrix construction of the characters. When stopped I have no
problems with even the small print. I have only seen one Fitsense and I
believe it uses LED's instead of LCD but they are of a smaller weight.
The Nike has backlighting that can be set to turn on whenever a button
is pushed or when you complete a "lap" I set my laps to one mile and it
is bright enough to catch my attention at night.
They are both based on the same technology and appear to have similar
degrees of accuracy, you probably can't go wrong either way.
> >I got the Fitsense because you can download it wirelessly to your
> >PC, and then upload to their website and look at the pretty graphs
> >and various other breakdowns of your stats.