What GPS to use?

[Jim Sherman]

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?

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? 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.

Possible with the GPS or with add-on software?

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

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.

Since I'm brand new to these things any advice is welcome. Thanks.

[Bob M]

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
> "Jim Sherman" > wrote in message
> ...
>> 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?
>>
>> 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? 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.
>>
>> Possible with the GPS or with add-on software?
>>
>> Mountable on a bike? Can you just carry it in your pocket?

Yes, they sell bike mounts.

>> 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.
>>
>> Since I'm brand new to these things any advice is welcome. Thanks.
>>
>
>
>
Mine does have features to stop and start routes and to mark "waypoints"
during the route. I don't know about elevation statistics, as I generally
don't look at these.


--
Bob M in CT
Remove 'x.' to reply

[Jim Spencer]

On Tue, 29 Jul 2003 11:49:31 -0400, Jim Sherman >
wrote:

Most any of the hand held GPS units should work for you. They all
will record your current track giving you location, time and some also
record elevation. I have an older Garmin Model(GPSIII) that I use on
my bike. It will record up to 1900 points and I can set the interval
that these points are taken based on any time or distance. Normally I
use .05 miles(95miles total) but you could use a smaller interval.
When I get back the track can be downloaded to the computer to be used
with any mapping program. Even if your GPS doesn't record elevation
some of those programs that have topographic maps will calculate total
climb and generate an elevation profile for you.

Also, except for cadence, a GPS will do everything your bike computer
will do and a whole lot more.

[Rick Onanian]

On Tue, 29 Jul 2003 11:49:31 -0400, 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?

I use an Etrex Venture. You can get a handlebar mount for the Etrex
series, though you won't find it in stores anymore, you should be
able to get it online or from Garmin. The handlebar mount is light,
onobtrusive, and very secure.

> 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? I

The Etrex Venture even comes with the computer cable in the box.
Other Etrex models don't (at least, cheaper ones).

> 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.

Again, score for the Etrex Venture. The Etrex line includes at
least two levels of breadcrumb-resolution. You won't find that
in any marketing literature, but I stumbled across it while
looking for some mapping software. Some Etrex models don't
breadcrumb very often, but the Etrex Venture is pretty quick.

Still, if you do a fast descent followed by a short climb, it
might miss the valley. Even while dropping multiple breadcrumbs,
it may not have a strong link to the satellites -- this is
especially true under heavy tree cover (another score for the
Etrex Venture, which supposedly handles tree cover pretty well).

> Possible with the GPS or with add-on software?

Absolutely.

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

Any Garmin Etrex series is mountable, via the handlebar mount
I mentioned before. It's never come off accidentally, even
after X amount of crashes. It does unclip easily when you want
it to.

Carrying a GPS in your pocket is a problem because the antenna
is directional; it has to face up. The Etrex antenna (probably
similar for all GPS) looks aesthetically like a largish computer
chip with a sticker on it, and the flat surface must face up
without excessive obstruction.

> 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.

You can always mark waypoints; that person forgot to do so.

Additionally, you could [gasp!] turn the gps off when you're in
your car. I only turn mine on when I actually want to use it.

Also...with the Etrex Venture [and probably all other Etrex as
well as most other GPS at all], you can tell it NOT to drop
breadcrumbs at all; then it just shows you where you are and
allows you to manually mark waypoints.

> Since I'm brand new to these things any advice is welcome. Thanks.

I've quite a bit of experience using mine on my mountain bike.
I'm lost without it...literally. ;)

--
Rick Onanian

[Rick Onanian]

On Tue, 29 Jul 2003 17:18:13 GMT, Jim Spencer > wrote:
> Also, except for cadence, a GPS will do everything your bike computer
> will do and a whole lot more.

I find that the readings from my bike computer are more accurate
and useful than those from the GPS, and easier to reset without
losing important data; but the GPS in combination with the bike
comp (which has cadence, I wouldn't do without it!), makes a
great team.

Now, integrate them, add a heart rate monitor, and let me write
scripts for it (maybe run Linux on it) and I'd be in heaven.

Power to the data! Data to the people!

Seriously speaking, though, that makes me think of this question
I have:
Is there a heart-rate monitor that takes constant readings without
requiring a chest band? Why haven't I seen any that read it from
the wrist? Aside from chest bands, I've only seen the ones that
read it from your fingertip, which is only useful when you've
stopped.

I've got enough things chafing and sweaty, I don't need to add a
damn chestband.

--
Rick Onanian

[archer]

In article >, says...
> On Tue, 29 Jul 2003 17:18:13 GMT, Jim Spencer > wrote:
> > Also, except for cadence, a GPS will do everything your bike computer
> > will do and a whole lot more.
>
> I find that the readings from my bike computer are more accurate
> and useful than those from the GPS, and easier to reset without
> losing important data; but the GPS in combination with the bike
> comp (which has cadence, I wouldn't do without it!), makes a
> great team.
>
> Now, integrate them, add a heart rate monitor, and let me write
> scripts for it (maybe run Linux on it) and I'd be in heaven.
>
> Power to the data! Data to the people!
>
> Seriously speaking, though, that makes me think of this question
> I have:
> Is there a heart-rate monitor that takes constant readings without
> requiring a chest band? Why haven't I seen any that read it from
> the wrist? Aside from chest bands, I've only seen the ones that
> read it from your fingertip, which is only useful when you've
> stopped.
>
> I've got enough things chafing and sweaty, I don't need to add a
> damn chestband.

Sweaty, yes, but I've never had any chafing from my Polar chestband.


--
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.

[Jim Sherman]

Thanks for your input Rick.

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?

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

Are these "breadcrumbs" marked by time or distance?

Jim

Rick Onanian wrote:
> On Tue, 29 Jul 2003 11:49:31 -0400, 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?
>
>
> I use an Etrex Venture. You can get a handlebar mount for the Etrex
> series, though you won't find it in stores anymore, you should be
> able to get it online or from Garmin. The handlebar mount is light,
> onobtrusive, and very secure.
>
>> 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? I
>
>
> The Etrex Venture even comes with the computer cable in the box.
> Other Etrex models don't (at least, cheaper ones).
>
>> 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.
>
>
> Again, score for the Etrex Venture. The Etrex line includes at
> least two levels of breadcrumb-resolution. You won't find that
> in any marketing literature, but I stumbled across it while
> looking for some mapping software. Some Etrex models don't
> breadcrumb very often, but the Etrex Venture is pretty quick.
>
> Still, if you do a fast descent followed by a short climb, it
> might miss the valley. Even while dropping multiple breadcrumbs,
> it may not have a strong link to the satellites -- this is
> especially true under heavy tree cover (another score for the
> Etrex Venture, which supposedly handles tree cover pretty well).
>
>> Possible with the GPS or with add-on software?
>
>
> Absolutely.
>
>> Mountable on a bike? Can you just carry it in your pocket?
>
>
> Any Garmin Etrex series is mountable, via the handlebar mount
> I mentioned before. It's never come off accidentally, even
> after X amount of crashes. It does unclip easily when you want
> it to.
>
> Carrying a GPS in your pocket is a problem because the antenna
> is directional; it has to face up. The Etrex antenna (probably
> similar for all GPS) looks aesthetically like a largish computer
> chip with a sticker on it, and the flat surface must face up
> without excessive obstruction.
>
>> 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.
>
>
> You can always mark waypoints; that person forgot to do so.
>
> Additionally, you could [gasp!] turn the gps off when you're in
> your car. I only turn mine on when I actually want to use it.
>
> Also...with the Etrex Venture [and probably all other Etrex as
> well as most other GPS at all], you can tell it NOT to drop
> breadcrumbs at all; then it just shows you where you are and
> allows you to manually mark waypoints.
>
>> Since I'm brand new to these things any advice is welcome. Thanks.
>
>
> I've quite a bit of experience using mine on my mountain bike.
> I'm lost without it...literally. ;)
>

[David Storm]

Depending on where you live, you can buy the handlebar mounts
at REI or Fry's electronics to name two retailers. I have an Etrex
Legend which has a built in map of major streets and trips in
the US and you can probably buy it with other parts of the
world depending on where you live. I use my GPS in concert
with Delorme's topographical software, Topo. With Topo
I can lay out a course on my desktop computer for a coming
ride or tour and download the route and waypoints to the GPS,
and whalla, I have the routes directions with turns and distances
in the GPS. You can go the other way too by going on a ride
and have the GPS track your course during a ride. You can
then upload the course to Topo and generate a route and
elevation profile in Topo. I have found the GPS very handy
when touring new and unknown roads and areas.

You can also purchase Garmin software which allows you to
download more detailed maps of streets and roads to the
GPS.

"Rick Onanian" > wrote in message
...
> On Tue, 29 Jul 2003 11:49:31 -0400, 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?
>
> I use an Etrex Venture. You can get a handlebar mount for the Etrex
> series, though you won't find it in stores anymore, you should be
> able to get it online or from Garmin. The handlebar mount is light,
> onobtrusive, and very secure.
>
> > 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? I
>
> The Etrex Venture even comes with the computer cable in the box.
> Other Etrex models don't (at least, cheaper ones).
>
> > 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.
>
> Again, score for the Etrex Venture. The Etrex line includes at
> least two levels of breadcrumb-resolution. You won't find that
> in any marketing literature, but I stumbled across it while
> looking for some mapping software. Some Etrex models don't
> breadcrumb very often, but the Etrex Venture is pretty quick.
>
> Still, if you do a fast descent followed by a short climb, it
> might miss the valley. Even while dropping multiple breadcrumbs,
> it may not have a strong link to the satellites -- this is
> especially true under heavy tree cover (another score for the
> Etrex Venture, which supposedly handles tree cover pretty well).
>
> > Possible with the GPS or with add-on software?
>
> Absolutely.
>
> > Mountable on a bike? Can you just carry it in your pocket?
>
> Any Garmin Etrex series is mountable, via the handlebar mount
> I mentioned before. It's never come off accidentally, even
> after X amount of crashes. It does unclip easily when you want
> it to.
>
> Carrying a GPS in your pocket is a problem because the antenna
> is directional; it has to face up. The Etrex antenna (probably
> similar for all GPS) looks aesthetically like a largish computer
> chip with a sticker on it, and the flat surface must face up
> without excessive obstruction.
>
> > 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.
>
> You can always mark waypoints; that person forgot to do so.
>
> Additionally, you could [gasp!] turn the gps off when you're in
> your car. I only turn mine on when I actually want to use it.
>
> Also...with the Etrex Venture [and probably all other Etrex as
> well as most other GPS at all], you can tell it NOT to drop
> breadcrumbs at all; then it just shows you where you are and
> allows you to manually mark waypoints.
>
> > Since I'm brand new to these things any advice is welcome. Thanks.
>
> I've quite a bit of experience using mine on my mountain bike.
> I'm lost without it...literally. ;)
>
> --
> Rick Onanian

[Mark Weaver]

I've been using a Magellan Sportrak Map on my bike recently. Kind of
overkill, but it has a moving map display which is actually pretty
nice--combined with street / topo maps. I can come back later and download
the tracks, which is mostly a curiosity, but I suppose I could actually make
my own trail maps that way. Altitude encoding isn't great, but it's not too
bad--I can look at a an altitude profile of my tracks after the fact. It's
surprising how well it does in tree cover--sometimes I lose the signal, but
it seems to hold it better on the bike than when walking. My guess it it's
somehow a kind of 'window fan' effect.

Anyway, here's a GPS track from riding the 'Potowatami Trail' (southern
Michigan) on Saturday. The straight line throught the lake is where I lost
the signal in dense tree cover:

http://www.fototime.com/C232670A6C1B8F0/orig.gif

Mark


"Jim Sherman" > wrote in message
...
> 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?
>
> 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? 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.
>
> Possible with the GPS or with add-on software?
>
> Mountable on a bike? Can you just carry it in your pocket?
>
> 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.
>
> Since I'm brand new to these things any advice is welcome. Thanks.
>

[Steve]

"Jim Sherman" > wrote in message

> 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?


Some useful sites to go along with all the useful posts.

http://joe.mehaffey.com/

http://mywebpages.comcast.net/ibikealot/navigatingbygps.htm

Steve B.

[Rick Onanian]

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

[Jim Spencer]

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

[B a r r y B u r k e J r .]

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

[B a r r y B u r k e J r .]

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

[Rick Onanian]

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

[archer]

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.

[Rick Onanian]

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

[Roberto Divia]

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

[salmoneous]

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.

[Rick Onanian]

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

[Roberto Divia]

Rick Onanian wrote:
> 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.

Not to mention the fact that you can't read the info (e.g. trip computer page)
without taking your helmet off :-(

> Mine's been safe on the handlebar.

So is mine ;-)

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

[James Messick]

Ditto. I have a Garmin eMap and it sucks for elevation. Otherwise it's
pretty cool. An external antenns helps when in the woods.

[Eric]

Actually, the altitude solution from a GPS is less accurate than the
latitude/longitude. This is mostly due to the fact that the GPS system
is up in the sky only. If there was a satellite or two at the center
of the Earth, the 3D mapping would be much more accurate. This has
been discussed in sci.geo.satellite-nav before, and there is an old
(outdated due to SA being turned off) Realaudio file at
http://www.tapr.org/tapr/ra/dcc97.intro.gps.ram if you are really
intrested in the technical details and a good overview of navagation
in general.

The e-Trex Vista has a built in barametric altimeter and magnetic
compass. The altimeter works very well, but I don't believe the
tracklog uses it (the tracklog uses GPS altitude). I still find it
very useful while climbing, though. The big improvement on the Vista
over the others is the large memory available for downloading maps.
For example, I keep most of the street level maps of the state of PA
loaded all the time.

One problem is that due to it bouncing around the countryside for
about 7000 miles on my handlebars, the compass no longer works.
However, I know that Garmin will repair it for a flat fee (basically
they send a new unit). I just don't think it is worth fixing, since I
rarely used it anyway.

Eric

archer > wrote in message >...
> 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.
>
> ....

[Ron Hardin]

Chris Malcolm 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?
>
> Those with barometric altimeters, e.g. Garmin Summit, Vista, MAP76S, &
> Geko 301.

I get fine altitudes with Garmin eTrex (variously $99-$125), the original.
Since the page button fell off after a couple years, I bought another and
now have two on the bike. Scotch electrical tape over a small wad of
durable plastic packing peanut material (there are various kinds, you need
a very flexible kind that won't break when you wad it up) fixed the missing
button, so it looks like I have two forever.

They agree about position to within a place in the last digit (might be
handlebar width! and altitude by about ten feet. Altitude will slowly
change but not wildly. Usually it goes slowly up when you pedal slowly
up and down when down. A tree canopy though will ruin it because the
number of satellites seen is greatly reduced.

Barometric altitude can be less accurate due to wind, which GPS altitude
is unaffected by.

I would say that if you bike in the open, so mostly you can see horizon to
horizon, the GPS altitude is fine. It will still change but is better at
detecting a slope than you are.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

[Ron Hardin]

Here's a test run, two Garman eTrex's on the handlebars, bike
parked out front, reading position and altitude every five minutes:
(decimal degrees, x's agree, alt feet, lat 40 degrees, average/good view of sky)

11:15 lat xx.xxx08 lon xx.xxx05 alt 1165 lat xx.xxx05 lon xx.xxx06 alt 1166
11:20 lat xx.xxx07 lon xx.xxx02 alt 1152 lat xx.xxx07 lon xx.xxx05 alt 1162
11:25 lat xx.xxx07 lon xx.xxx03 alt 1162 lat xx.xxx07 lon xx.xxx05 alt 1157
11:30 lat xx.xxx06 lon xx.xxx03 alt 1160 lat xx.xxx07 lon xx.xxx04 alt 1162
11:35 lat xx.xxx07 lon xx.xxx04 alt 1157 lat xx.xxx06 lon xx.xxx03 alt 1169
11:40 lat xx.xxx08 lon xx.xxx03 alt 1146 lat xx.xxx06 lon xx.xxx04 alt 1164
11:45 lat xx.xxx07 lon xx.xxx03 alt 1153 lat xx.xxx06 lon xx.xxx04 alt 1163
11:50 lat xx.xxx07 lon xx.xxx03 alt 1154 lat xx.xxx07 lon xx.xxx03 alt 1142
11:55 lat xx.xxx07 lon xx.xxx03 alt 1142 lat xx.xxx06 lon xx.xxx03 alt 1158
12:00n lat xx.xxx08 lon xx.xxx04 alt 1151 lat xx.xxx05 lon xx.xxx04 alt 1162

the variation is slow (ie this captures it well, it's not changing faster)
corresponding to satellite movement and (probably) deficiencies in the refraction
correction, rather than measurement noise. The two eTrex's are different system
releases, current and then previous.

Now, over 45 minutes, you've gone over ten miles, and 20 feet over ten miles
is two feet over a mile, or a pretty good grade estimate.

Probably, if you see fast altitude variation, it's trees cutting out satellites,
which lets the errors in the refraction correction cut in and out at the same speed.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

[Chris Malcolm]

Ron Hardin > writes:

>Here's a test run, two Garman eTrex's on the handlebars, bike
>parked out front, reading position and altitude every five minutes:
>(decimal degrees, x's agree, alt feet, lat 40 degrees, average/good view of sky)

>11:15 lat xx.xxx08 lon xx.xxx05 alt 1165 lat xx.xxx05 lon xx.xxx06 alt 1166
>11:20 lat xx.xxx07 lon xx.xxx02 alt 1152 lat xx.xxx07 lon xx.xxx05 alt 1162
>11:25 lat xx.xxx07 lon xx.xxx03 alt 1162 lat xx.xxx07 lon xx.xxx05 alt 1157
>11:30 lat xx.xxx06 lon xx.xxx03 alt 1160 lat xx.xxx07 lon xx.xxx04 alt 1162
>11:35 lat xx.xxx07 lon xx.xxx04 alt 1157 lat xx.xxx06 lon xx.xxx03 alt 1169
>11:40 lat xx.xxx08 lon xx.xxx03 alt 1146 lat xx.xxx06 lon xx.xxx04 alt 1164
>11:45 lat xx.xxx07 lon xx.xxx03 alt 1153 lat xx.xxx06 lon xx.xxx04 alt 1163
>11:50 lat xx.xxx07 lon xx.xxx03 alt 1154 lat xx.xxx07 lon xx.xxx03 alt 1142
>11:55 lat xx.xxx07 lon xx.xxx03 alt 1142 lat xx.xxx06 lon xx.xxx03 alt 1158
>12:00n lat xx.xxx08 lon xx.xxx04 alt 1151 lat xx.xxx05 lon xx.xxx04 alt 1162

>the variation is slow (ie this captures it well, it's not changing faster)
>corresponding to satellite movement and (probably) deficiencies in the refraction
>correction, rather than measurement noise. The two eTrex's are different system
>releases, current and then previous.

Looks fairly typical to me. It's the sort of altitude dithering which
a barometric altimeter will greatly reduce.

>Now, over 45 minutes, you've gone over ten miles, and 20 feet over ten miles
>is two feet over a mile, or a pretty good grade estimate.

Fair enough. Some folk are fussier about altitude profiles and move
slower, e.g., folk climbing hills on foot (and hand), and who might
want to use small ups and downs in altitude as navigational clues.

>Probably, if you see fast altitude variation, it's trees cutting out satellites,
>which lets the errors in the refraction correction cut in and out at the same speed.

And this can happen if you're stationary near a big tree and
satellites move through its large branches. It can happen if a wind is
moving the tree branches around. Rapid (< few minutes) variation won't
necessarily be observed in any particular half hour, but it's common
enough in a trip that you never know whether it's happened or not. For
example, suppose in a trip at one point in ten minutes you climbed 15
feet. But the trip log shows two such incidents. Which one is the real
one and which is the dither?








--
Chris Malcolm +44 (0)131 650 3085 DoD #205
School of Informatics, Edinburgh University, 5 Forrest Hill,
Edinburgh, EH1 2QL, UK. [http://www.dai.ed.ac.uk/homes/cam/ ]