What GPS to use?

On Tue, 29 Jul 2003 14:59:06 -0400, Jim Sherman wrote:
A few more questions. Does the Venture calculate elevation? The
comparison chart shows that only the Vista has a barometric altimeter. Or
is that just an advanced version?

Now that you mention it, I believe it does not use an altimeter,
but just figures it from the satellite signal. I don't know just
how accurate this method is.

Does the Etrex come with any software for downloading (even a basic
program) or is that an add-on?

It does not come with any program. Free (open source, free software)
is available for it, as well as free (free of charge) and shareware,
and of course, commercial software.

Are these "breadcrumbs" marked by time or distance?

I call 'em breadcrumbs [a la Hansel & Gretel]; Garming calls
them Tracklogs, I'm sure others call them other things. Anyway,
on the Garmin Etrex series, they are marked by time. Somebody
else replied with a GPS that marks by distance, and suggested
that you may be able to adjust it.

I think that very accurate mapping via GPS on a bicycle may not
be feasible...you may have to walk, with any GPS, to get the
accurate map you want.

I'm rather interested in this subject, as I'd like to map the
Big River Management Area, a large network of moderate to very
good singletrack near my home. Currently, only very rudimentry
maps exist and are hard to find. I've got loads of GPS data,
but it's such a damn mess, I have to start fresh.

I'd be interested in whatever general GPS cartography information
you come up with, as well as what program you choose.

That all said...did I mention that I LOVE my Etrex Venture?

Jim
--
Rick Onanian

On Tue, 29 Jul 2003 21:08:05 -0400, Rick Onanian
wrote:

snip
Are these "breadcrumbs" marked by time or distance?

I call 'em breadcrumbs [a la Hansel & Gretel]; Garming calls
them Tracklogs, I'm sure others call them other things. Anyway,
on the Garmin Etrex series, they are marked by time. Somebody
else replied with a GPS that marks by distance, and suggested
that you may be able to adjust it.


I looked at the manual for the eTrex Venture
(http://www.garmin.com/manuals/133.pdf) and like my GPSIII the
interval for taking track points can be based on distance or time.
Distance can be set from 0 to 9.9miles and time can be set up to
99hrs:59min:59sec

On Tue, 29 Jul 2003 16:14:59 GMT, "Alan Acock"
wrote:

I don't have anything to contribute other than a question. A friend has one
of these (I don't even know the brand), and it seems to give wildly
inaccurate elevations (below sea level in the hills). Do some do a better
job of elevation and do any have a useful slope gauge?
Alan


Some units have barometric altimeters which are more accurate than the
altitude calculated from the satellites.

However, these need to be set to the proper altitude when powered on,
and readjusted occasionally as weather changes.

Barry

On Tue, 29 Jul 2003 13:58:06 -0400, Rick Onanian
wrote:

Again, score for the Etrex Venture. The Etrex line includes at
least two levels of breadcrumb-resolution.

The eTrex Vista is fully configurable to make marks by time or
distance. The time and distance intervals can be programmed by the
user.

I don't know about the Venture, but the Vista can currently store
10,000 track log points. That's about 2 hours and 45 minutes at the
maximum resolution by time of 1 point per second, and 100 miles at the
maximum distance resolution of .01 mile per point.

Barry

On Wed, 30 Jul 2003 03:08:28 GMT, Jim Spencer wrote:
I looked at the manual for the eTrex Venture
(http://www.garmin.com/manuals/133.pdf) and like my GPSIII the
interval for taking track points can be based on distance or time.
Distance can be set from 0 to 9.9miles and time can be set up to
99hrs:59min:59sec

How about that...I learn something new every day. I might just
fiddle around with that!

Thanks.

--
Rick Onanian

In article , says...
On Tue, 29 Jul 2003 14:59:06 -0400, Jim Sherman wrote:
A few more questions. Does the Venture calculate elevation? The
comparison chart shows that only the Vista has a barometric altimeter. Or
is that just an advanced version?

Now that you mention it, I believe it does not use an altimeter,
but just figures it from the satellite signal. I don't know just
how accurate this method is.

The altitude accuracy is the same as the horizontal accuracy: typicallt
10 to 30 ft, depending on conditions. It simply determines your position
in 3-dimensional space with respect to the satellites.

.....

--
David Kerber
An optimist says "Good morning, Lord." While a pessimist says "Good
Lord, it's morning".

Remove the ns_ from the address before e-mailing.

On Wed, 30 Jul 2003 11:07:45 GMT, B a r r y B u r k e J r .
wrote:
I think that very accurate mapping via GPS on a bicycle may not
be feasible...

It certainly is when the GPS is set up right and the logs are
downloaded to GOOD maps like those from National Geographic or
Maptech, as opposed to Garmin's inaccurate maps.

Also keep in mind that saving a tracklog inside the GPS causes it to
be compressed, detail is removed to make the log take less storage
memory. Downloading each track log while it's still the active log
will preserve the detail.

It seems to me that you've put much more time and effort into
doing this than I have. I haven't bothered with existing maps,
nor have I saved any tracklogs inside the GPS -- I just download
them when I get back from the ride.

I think that the Etrex Vista that you use is the top-of-the-line
Etrex model, isn't it? For anybody willing to spend the money, it's
got to be as good or a better choice than my Etrex Venture, which
is the best value Etrex for bike-mapping; going to more expensive
models may not yield any advantage for bike mapping...except that,
I think, the Vista has some 8mb memory and the Venture has something
like 1mb.

However much memory it has, it's more than enough to just ignore
my tracklog (never bother saving), and the GPS keeps damn near all
the trails I ride in memory. I look at the map and see a huge,
gnarled mess, until I zoom in. The detail at the default settings
is sufficient for trail mapping, IMO, and yields a lot of memory
space.

Barry
--
Rick Onanian

Jim Sherman wrote:
I have never used a GPS before but would like to get one to calculate
elevation, grades etc especially on hilly routes. My cycle computer
already has speed distance etc. The Garmin Etrex seems to get the most
positive reports. But that's from the general public. How about bikers?

Garmin Etrex Vista. Baro and GPS altimetry, sampling automatic, by time or
by distance. Computer link via RS232. Proprietary and non-propietary
software for downloading and analysis. Good resolution (max: 2 meters).

I'm not too interested in preprogrammed routes (though I probably will
after I get it). More interested in downloading data to a computer
after a ride to get a visual display of what I have done. Will it do
this?

Yes: detailed for the route, a bit less for the altimetry. You need extra
software.

I expect it must update your position extremely frequently or
even constantly otherwise a slow climb followed by a fast descent would
give a strange readout.

I find it's OK with a 50 meters sampling.

Possible with the GPS or with add-on software?

Both.

Mountable on a bike? Can you just carry it in your pocket?

Yes and yes. Garmin sells a special bike holder. The best position seems
to be on the helmet, a "soft" holder from Garmin can be used for that
(heard of, never tried myself).

I read someone's post about how he had to edit his route after
downloading as it included his car ride home! I would expect it to have
some kind of mark feature to mark beginning and ends of routes.

There are two types of tracks: "live" and "saved". Live tracks include all
data. Saved track discard timing information. The unit splits tracks in
chunks based on "pauses" (loss of GPS signal or breaks). The software from
Garmin allows deletion of (sets of) points as well as deletion of entire
chunks.

I normally export from the Garmin software to Excel with a cut-and-paste
operation. Takes a few seconds.

Ciao,
--
Roberto Divia` Love at first sight is one of the greatest
============= labour-saving devices the world has ever seen.
Mailbox: C02110 CERN-European Organization for Nuclear Research
E-mail: CH-1211 GENEVE 23, Switzerland

Another option that might work (depending upon where you ride) is Topo
software. It doesn't track where you actually rode, per se. It shows
you maps where you then trace out your route. It then can tell you the
distance, give you an elevation map, etc.

On Wed, 30 Jul 2003 15:05:08 +0200, Roberto Divia
wrote:
Yes and yes. Garmin sells a special bike holder. The best position seems
to be on the helmet, a "soft" holder from Garmin can be used for that
(heard of, never tried myself).

That never occured to me, but it would probably yield more accurate
results and less signal loss.

However, there, you won't know when you've lost a signal; and also,
it's subject to getting destroyed in an accident.

Mine's been safe on the handlebar.
--
Rick Onanian