# What capabilities do I lose without barometric altimeter?



## likeybikey (Nov 24, 2007)

The new Garmin Forerunner 245 seems like it does everything I want, and the battery life is much better than similarly priced, older Garmins. One thing people seem to be complaining about, though, is the device's lack of a barometric altimeter. 

I don't know if I need a barometric altimeter. My first question is, what capabilities do I lose without one?

I think a barometric altimeter might be for 
-real-time altitude data
-stair-climbing data
-I saw some mention that power data needs a barometer?

It is very remotely possible I will get sucked in to the abundance of data these little devices can provide and suddenly find myself wanting something only a barometric altimeter provides. But my use today (via my smartphone) is simply to press record on Strava, go for a ride or run, and look at the results when I get home. I think Strava (and other software) recalculates (or can recalculate) everything anyway. So my second question is, for that type of use am I losing anything at all?


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## ghettocruiser (Jun 21, 2008)

Strava will default to using basemap elevation data to determine your climbing and descending, which in practice is almost always less than what you'd record with a barometer. 

So if you join strava climbing challenges, you are likely to be ripped off.

Strava's power calculations are pretty questionable, so your're not missing anything there IMO. A power meter that measured force directly does not need elevation data of any type.

That's about all I can think of.


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## Lone Rager (Dec 13, 2013)

Grade info during a ride is best based on baro as GPS elevation is generally less accurate and noisier than lat lon due to sat geo. Even with baro, Garmins have not been very good at this.


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## Harold (Dec 23, 2003)

if you care about elevation AT ALL at any time (real-time or post-activity), then you want a barometer.

elevation accuracy. resolution for change in elevation. grade. anything that depends on elevation will get mucked up if you don't have a barometric altimeter.


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## likeybikey (Nov 24, 2007)

I would have thought the topo maps would be a bit more reliable, Harold. Would you say the issue is that the data doesn't account for all the little ups and downs that go into a climb? 

Thanks all, for your replies. Gives me some things to think about in terms of what I want out of a device beyond good battery life and buttons. 

Sent from my Pixel using Tapatalk


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## ghettocruiser (Jun 21, 2008)

Other weird things happen when strava creates your altitude plot from a digital elevation model/map.

On flat railtrail in that goes through a hilly area, I was getting some big, false elevation changes since the elevation model was not fine enough to see the flat skinny trail.

Elsewhere, on a trail that went along the flat edge of a steep cliff, strava had me going halfway down said cliff and coming back up repeatedly, since the elevation model generalized the cliff into a slope that covered more ground than it should.

The ugly flip side to barometric altimeters is when they make up topography due to changes in weather, or when the ports get blocked by mud or water.


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## Harold (Dec 23, 2003)

likeybikey said:


> I would have thought the topo maps would be a bit more reliable, Harold. Would you say the issue is that the data doesn't account for all the little ups and downs that go into a climb?
> 
> Thanks all, for your replies. Gives me some things to think about in terms of what I want out of a device beyond good battery life and buttons.
> 
> Sent from my Pixel using Tapatalk


Elevation models are generally on a 30m pixel size, so LOTS of small changes in elevation get missed.

Higher resolution elevation models are being developed, but thet create other problems because the accuracy of a given elevation becomes dependent on the positional accuracy of the gps. In areas with high relief/steep slopes, a very small reduction in positional accuracy can make for false readings, which has already been mentioned, but will be magnified.

Sent from my VS995 using Tapatalk


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