Re: Elevation estimates - more

In message <49fb0d50$0$8254$ec3e2dad@xxxxxxxxxxxxxxxxxxxxxx>
"Mike Mason" <mikemason@xxxxxxxxxxxxxx> wrote:


"Paul Saunders" <pvs1@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:nrmdnVj-YMWMa2fUnZ2dnUVZ8rudnZ2d@xxxxxxxxxxxx
Mike Clark wrote:
"Mike Mason" wrote:

No disappointment that Garmin's advertising as far as the barometer
goes is basically a lie

I can't remember exactly what was claimed in the advertising but I
own a Summit, a Geko301 and a Vista HCx. I've been more than pleased
with the performance, particularly the autocalibration mode, which
seems to work very well under most conditions.

Same here.

As you've noted, the downside of that sensitivity and resolving power
is that it records small pressure fluctuations in gusty environments.
However if it wasn't as sensitive you wouldn't be able to resolve
small altitude differences in still air conditions.

Exactly. I suppose the real question is, how often do you go out walking
in very windy conditions? If you do so often enough that it's a real
problem then maybe you should buy a non-altimeter GPS instead/as well?

It's a pity that you can't switch between altimeter and non-altimeter
mode. No reason in theory why that shouldn't be possible. It would be even
better if it recorded two tracks simulaneously, one altimeter track and
one GPS elevation track.

Paul
Quick look at 2008/2009 indicates that I did 47 walks in and around
the Lake District. For me 2008/2009 was a poor year for weather as a
quick check on my photographs indicates that. Most of those walks
were done in poor conditions with about a third with wind having some
impact on the walk.

My ethos on walking is go out and do something whatever the weather. I
will change route to suit the weather but only if in my estimation
the weather is so bad as to make the walk inherently dangerous.This
sounds and probably is arrogant but if I were to walk only when the
weather is good then I wouldn't do much walking in this country.

Absolutely agree with you on this one. I rarely let the weather stop me
from going out and it's only very extreme conditions that make a big
influence on route choice. I've done a fair bit of crawling on hands and
knees and navigation in white outs.


I do have an Extrex Vista, which is less prone to being affected by
the wind but is nowhere near as precise/accurate (which) as the 60cxs

Garmin's advertising for the 60cxs includes the statement 'Barometric
altimeter provides extremely accurate elevation data'.

Garmin's advertising for the Vista includes 'The Vista's barometric
altimeter pinpoints your precise altitude'.

Both of these statements are not qualified in any way

Mike


I think the Vista HCx has a similar chipset to the 60cxs? As far as I am
aware the major improvements in those models over the older Vista and
Summit models relates to the GPS components, not the barometric
components.

I do think there is a problem with the advertising of the barometric
models if the audience is largely made up of individuals who have no
previous experience of using a barometric altimeter alone. I've used
barometric altimeters for navigation, particularly in mountaineering and
ski-mountaineering before I acquired a GPS. Therefor I had experience of
the problems associated with calibration of these devices under
different weather conditions. Thus when I purchased my first GPS, an
etrex Summit, it performed to my expectations, but with the advantage
that I could autocalibrate the barometer with the averaging of GPS
readings.

I also have become aware that many users of these barometric GPSs are
not aware of the importance of manual calibration of the device at the
beginning of each day/walk and also at regularly intervals throughout
the day (e.g. just before switching the unit off for any short period)
and thus they simply leave it in the auto mode all the while. I agree
that for many users that don't bother to do this regular manual
recalibration they would be much better off not buying the barometric
devices.

Mike
--
o/ \\ // |\ ,_ o Mike Clark
<\__,\\ // __o | \ / /\, "A mountain climbing, cycling, skiing,
"> || _`\<,_ |__\ \> | caving, antibody engineer and
` || (_)/ (_) | \corn computer user"
.

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