Sarah

Link with info on calibration/accuracy of GPS altimiters vs barometric altimeters:

http://wiki.motionbased.com/mb/GPS_Barometric_Altimeter

Answers the questions below.

Sarah

----- Original Message ----
From: Rick Johnson
To: obra@list.obra.org
Sent: Tuesday, January 16, 2007 6:00:19 PM
Subject: Re: [OBRA Chat] Garmin 305 questions

Ron Magnus wrote:
"In most altimeters one has to set in the barometric pressure correction to indicate the local correct elevation above sea level. There is no human intervention on the 305 so I conclude that it probably gets some data from above but I doubt it's devine."

Another possibility is that as the 305 is not intended for navigation
the altitude is not calibrated at all - possibly just assumes a standard
pressure of 29.92. This will be just fine for the use the 305 is
intended - tracking relative gain/loss - as the pressure change over the
course of a workout will usually not be significant.
Other Garmin units I have used allow the barometric altimeter to be
calibrated with various known conditions such as actual altitude or
current pressure. Again this only matters in navigation where route
finding/orienteering requires knowing the altitude to a high degree of
accuracy. I use my Vista to track workouts but never bother to calibrate
the altimeter unless I'm mapping or navigating altitude critical routes.

Rick

Ron Magnus wrote:

>There was a comment about some operation issues with the '305 and a
>suspicion of an update.
>
>
>There has been a number of posts on the http:/www.motionbased forums about
>battery life and ways to extend it as well as talk about firmware updates.
>Right now the current firmware for the 305 is 2.9 dated sometime in
>December. The 26th comes to mind. The latest chipset load is from
>November and I don't recall the number.
>
>You can detrimine the version when you first turn on the unit and look at
>the page prior to it starting to aquire satelites. The firmware and
>chipset loads are avialable from Garmin. I believe they have notes to
>tell you what was rewritten for each revision. If you are geekish you may
>find it interesting to see what needed to be improved that you had not
>noticed.
>
>As for altitude determination, yes the owner's manual states the the
>information is barometric. Based on altitude errors noted at turn on and
>start of the ride as compared to the elevation at the end of the ride at
>the start point which is usually pretty close, I am inclined to think that
>there is more than barometric data being crunched. In most altimeters one
>has to set in the barometric pressure correction to indicate the local
>correct elevation above sea level. There is no human intervention on the
>305 so I conclude that it probably gets some data from above but I doubt
>it's devine.
>
>Ron
>
>_______________________________________________
>OBRA mailing list
>obra@list.obra.org
>http://list.obra.org/mailman/listinfo/obra
>Unsubscribe: obra-unsubscribe@list.obra.org
>
>
>

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David
Turn off the auto pause when mountain bike riding or change the low speed to .5 miles an hour on the auto pause. I have used the Garmin 305 at the Ski Bowl and never lost any function.

> From: ibis23@comcast.net> To: paul.formiller@maxtek.com; obra@list.obra.org> Date: Tue, 16 Jan 2007 17:12:58 -0800> Subject: Re: [OBRA Chat] Garmin 305 questions> > In response to the question about reception when mountain biking: It> depends. I have raced with it at Ski Bowl and I would hear the constant> chirping the unit auto-pausing and auto-resuming as I was going through the> tree cover. It would seem that if the forest is dense enough, you will lose> the signal every now and then. That being said, my data was only off by a> bit as the results were shortened due to the loss of signal.> > However, I have ridden with it at Brown's camp and it worked fine. > > The cadence sensor is supposed to take care of when you lose the signal. Due> to the fact that it is continually tracking your speed, cadence, etc, there> is supposed to be minimal loss of data. (Of course I have yet to install my> cadence sensor because I was having problems getting it to work right...)> > In response to the other questions:> 2) Never taken it out longer than a 4 hour ride and it worked fine. > 3) Not sure about that. It was accurate right out of the box.> 4) Works fine in the rain, snow, and sunny weather. No complaints here.> > Dave> > -----Original Message-----> From: obra-bounces@list.obra.org [mailto:obra-bounces@list.obra.org] On> Behalf Of Paul Formiller> Sent: Tuesday, January 16, 2007 1:17 PM> To: obra@list.obra.org> Subject: [OBRA Chat] Garmin 305 questions> > Thanks for all the responses on the Garmin 305. I'm specifically interested> in the following questions. I'm an elevation tracking junky. I current use> a Polar 710 with a barometric altimeter.> > 1) How's the signal reception for the Garmin? Any experience mountain> biking (trees, hills, etc). I'm concerned about losing the signal - (losing> speed, miles, elevation, etc).> > 2) I've heard issues about battery life. Can it last 10 hours + (sorry I'm> a tourist on the RAMROD)?> > 3) I hear for accurate elevation, you need to upload to the Motion Based> software. Is this true?> > 4) Any opinions on GPS versus barometric elevation accuracy. Seems like GPS> should be better (not weather dependent).> > > Thanks for the input!!! It's helpful when you didn't get one for Christmas> and you have to buy it (hoping for a tax refund).> > > Paul> _______________________________________________> OBRA mailing list> obra@list.obra.org> http://list.obra.org/mailman/listinfo/obra> Unsubscribe: obra-unsubscribe@list.obra.org> > > _______________________________________________> OBRA mailing list> obra@list.obra.org> http://list.obra.org/mailman/listinfo/obra> Unsubscribe: obra-unsubscribe@list.obra.org
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Rick Johnson

Ron Magnus wrote:
"In most altimeters one has to set in the barometric pressure correction to indicate the local correct elevation above sea level. There is no human intervention on the 305 so I conclude that it probably gets some data from above but I doubt it's devine."

Another possibility is that as the 305 is not intended for navigation
the altitude is not calibrated at all - possibly just assumes a standard
pressure of 29.92. This will be just fine for the use the 305 is
intended - tracking relative gain/loss - as the pressure change over the
course of a workout will usually not be significant.
Other Garmin units I have used allow the barometric altimeter to be
calibrated with various known conditions such as actual altitude or
current pressure. Again this only matters in navigation where route
finding/orienteering requires knowing the altitude to a high degree of
accuracy. I use my Vista to track workouts but never bother to calibrate
the altimeter unless I'm mapping or navigating altitude critical routes.

Rick

Ron Magnus wrote:

>There was a comment about some operation issues with the '305 and a
>suspicion of an update.
>
>
>There has been a number of posts on the http:/www.motionbased forums about
>battery life and ways to extend it as well as talk about firmware updates.
>Right now the current firmware for the 305 is 2.9 dated sometime in
>December. The 26th comes to mind. The latest chipset load is from
>November and I don't recall the number.
>
>You can detrimine the version when you first turn on the unit and look at
>the page prior to it starting to aquire satelites. The firmware and
>chipset loads are avialable from Garmin. I believe they have notes to
>tell you what was rewritten for each revision. If you are geekish you may
>find it interesting to see what needed to be improved that you had not
>noticed.
>
>As for altitude determination, yes the owner's manual states the the
>information is barometric. Based on altitude errors noted at turn on and
>start of the ride as compared to the elevation at the end of the ride at
>the start point which is usually pretty close, I am inclined to think that
>there is more than barometric data being crunched. In most altimeters one
>has to set in the barometric pressure correction to indicate the local
>correct elevation above sea level. There is no human intervention on the
>305 so I conclude that it probably gets some data from above but I doubt
>it's devine.
>
>Ron
>
>_______________________________________________
>OBRA mailing list
>obra@list.obra.org
>http://list.obra.org/mailman/listinfo/obra
>Unsubscribe: obra-unsubscribe@list.obra.org
>
>
>

Ron Magnus

There was a comment about some operation issues with the '305 and a
suspicion of an update.

There has been a number of posts on the http:/www.motionbased forums about
battery life and ways to extend it as well as talk about firmware updates.
Right now the current firmware for the 305 is 2.9 dated sometime in
December. The 26th comes to mind. The latest chipset load is from
November and I don't recall the number.

You can detrimine the version when you first turn on the unit and look at
the page prior to it starting to aquire satelites. The firmware and
chipset loads are avialable from Garmin. I believe they have notes to
tell you what was rewritten for each revision. If you are geekish you may
find it interesting to see what needed to be improved that you had not
noticed.

As for altitude determination, yes the owner's manual states the the
information is barometric. Based on altitude errors noted at turn on and
start of the ride as compared to the elevation at the end of the ride at
the start point which is usually pretty close, I am inclined to think that
there is more than barometric data being crunched. In most altimeters one
has to set in the barometric pressure correction to indicate the local
correct elevation above sea level. There is no human intervention on the
305 so I conclude that it probably gets some data from above but I doubt
it's devine.

Ron

David Rosen

In response to the question about reception when mountain biking: It
depends. I have raced with it at Ski Bowl and I would hear the constant
chirping the unit auto-pausing and auto-resuming as I was going through the
tree cover. It would seem that if the forest is dense enough, you will lose
the signal every now and then. That being said, my data was only off by a
bit as the results were shortened due to the loss of signal.

However, I have ridden with it at Brown's camp and it worked fine.

The cadence sensor is supposed to take care of when you lose the signal. Due
to the fact that it is continually tracking your speed, cadence, etc, there
is supposed to be minimal loss of data. (Of course I have yet to install my
cadence sensor because I was having problems getting it to work right...)

In response to the other questions:
2) Never taken it out longer than a 4 hour ride and it worked fine.
3) Not sure about that. It was accurate right out of the box.
4) Works fine in the rain, snow, and sunny weather. No complaints here.

Dave

-----Original Message-----
From: obra-bounces@list.obra.org [mailto:obra-bounces@list.obra.org] On
Behalf Of Paul Formiller
Sent: Tuesday, January 16, 2007 1:17 PM
To: obra@list.obra.org
Subject: [OBRA Chat] Garmin 305 questions

Thanks for all the responses on the Garmin 305. I'm specifically interested
in the following questions. I'm an elevation tracking junky. I current use
a Polar 710 with a barometric altimeter.

1) How's the signal reception for the Garmin? Any experience mountain
biking (trees, hills, etc). I'm concerned about losing the signal - (losing
speed, miles, elevation, etc).

2) I've heard issues about battery life. Can it last 10 hours + (sorry I'm
a tourist on the RAMROD)?

3) I hear for accurate elevation, you need to upload to the Motion Based
software. Is this true?

4) Any opinions on GPS versus barometric elevation accuracy. Seems like GPS
should be better (not weather dependent).

Thanks for the input!!! It's helpful when you didn't get one for Christmas
and you have to buy it (hoping for a tax refund).

Paul
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OBRA mailing list
obra@list.obra.org
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Unsubscribe: obra-unsubscribe@list.obra.org

oregonyankee@comcast.net

Paul

The signal reception is excellent. I get links even in the house. No problem there.

Not enough experience with it to comment on battery life. Yeah, I've heard the same and have had similar concern as I do long rides as well. However, the benefits outweigh that one shortcoming, in my opinion. You can pick up a USB based batter to battery charger - might even work on the bike, for all I know.

The elevation seems to be more accurate than what I was seeing on my Ciclosport CM434M. Again, not enough time to truly compare. But, as the 305 uses both barometric and satellite for elevation, it should be more accurate (at least that's my understanding).

One more thing. If you opt for the Cadence feature, you can run the 305 for distance, time and speed without turning on the satelllite function. That would preserve some battery life, I would imagine. You could also shut off the HRM function for more life. Yeah, that all kind defeats the purpose but, as I said, how many rides over six or seven hours do you do? For me, it's fine.

Peter

--
Bored? Boss not looking? Surf over to my cycling blog at:
www.OregonLive.com/weblogs/bikeblog/

-------------- Original message --------------
From: Paul Formiller

> Thanks for all the responses on the Garmin 305. I'm specifically interested in
> the following questions. I'm an elevation tracking junky. I current use a
> Polar 710 with a barometric altimeter.
>
> 1) How's the signal reception for the Garmin? Any experience mountain biking
> (trees, hills, etc). I'm concerned about losing the signal - (losing speed,
> miles, elevation, etc).
>
> 2) I've heard issues about battery life. Can it last 10 hours + (sorry I'm a
> tourist on the RAMROD)?
>
> 3) I hear for accurate elevation, you need to upload to the Motion Based
> software. Is this true?
>
> 4) Any opinions on GPS versus barometric elevation accuracy. Seems like GPS
> should be better (not weather dependent).
>
>
> Thanks for the input!!! It's helpful when you didn't get one for Christmas and
> you have to buy it (hoping for a tax refund).
>
>
> Paul
> _______________________________________________
> OBRA mailing list
> obra@list.obra.org
> http://list.obra.org/mailman/listinfo/obra
> Unsubscribe: obra-unsubscribe@list.obra.org

Paul Formiller

Thanks for all the responses on the Garmin 305. I'm specifically interested in the following questions. I'm an elevation tracking junky. I current use a Polar 710 with a barometric altimeter.

1) How's the signal reception for the Garmin? Any experience mountain biking (trees, hills, etc). I'm concerned about losing the signal - (losing speed, miles, elevation, etc).

2) I've heard issues about battery life. Can it last 10 hours + (sorry I'm a tourist on the RAMROD)?

3) I hear for accurate elevation, you need to upload to the Motion Based software. Is this true?

4) Any opinions on GPS versus barometric elevation accuracy. Seems like GPS should be better (not weather dependent).

Thanks for the input!!! It's helpful when you didn't get one for Christmas and you have to buy it (hoping for a tax refund).

Paul