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Sunday, March 18, 2012

Why have a barometric altimeter?

Altimeter

NOTE: A much more current version of this post can be found here.

Quite simply, the primary reason you would want a barometric altimeter in a handheld GPS is for more accurate elevation readings. This is especially useful for bikers, hikers and atheletes in training. You can use the resulting data to track your progress and maintain an accurate record of your trips. A barometric altimeter can also help you accurately place your location on a topo map.

Furthermore, you can use the altimeter to forecast weather trends. A falling barometer can indicate worsening weather. See the barometer section of this review for some really cool things you can do with your GPS!

GPS-based altitude error is generally worse than latitude/longitude error. A good explanation of why barometric altimeters are better than GPS-based elevation data comes from GPSInformation.net. Here is another good resource — an electronic compass and barometric altimeter FAQ from Garmin.

Finally, a barometric altimeter is often paired with an electronic compass in higher end handheld GPS receivers.

Related post:

About Rich Owings

Rich is the owner, editor and chief bottle-washer for GPS Tracklog. Connect with him on Twitter, Facebook or Google Plus.

Comments

  1. Thanks for this post. I was wondering this question a few weeks ago. (I searched your site for some info, but this is really what I was after. I knew that if I just waited patiently, you’d get to it eventually!;)
    So its all to do with geometry. Glad I got that altimeter watch when it was on sale then.
    k

  2. Thanks Keith. There are a LOT of posts that I want to get around to eventually! What I should have added in this post is how much I LOVE my altimeter. When I’m biking I only have two fields showing on the map screen. One of them is always elevation.

  3. Glen Arseneault says:

    Hi, Would you know which auto gps systems have a barometric altimeter? I know the magellan model 4210 has one but not sure which other models offer that option. Thank you

  4. I’ve never heard of an auto GPS with a barometric altimeter, and I don’t see it listed in the 4210’s specs. Why would you want this on an auto GPS?

  5. Hi,
    I have got totally different opinion. Since good 15 years I’m using different cycle computers with baro altimeter, and I’m highly dissapointed with them, regarding up to 200m in one day error appearing if weather changes. It makes them sometimes almost useless for cycling.
    I was waiting long time for accurate GPS. Unfortunatelly bike Garmin models are equipped with baro altimeters. Recently during 3 weeks Alpine cycling we have used cheap Nokia car navigation (free gift to new Skoda cars) to adjust our cycle computers. This Nokia has GPS altimeter, and we found it always roughly 1 metre accurate comparing to conour lines, and altitude points on the maps. Simply NO WEATHER INFLUENCE!
    If there is any problem with portable GPS (e.g.high power demand fort this feature), I just can’t understand, why nobody makes navigation devices with altitude based on pre-loaded memory, like contours on the maps, while they are already fully packed with other map based informations requiring thousands times more memory, than 10, or 20metres contours.
    When I suggested that to Garmin, tech. department gave me stupid answer, like “you can pre-adjust your altitude every day before you start riding”.

  6. Thats also my reason to use GPS-BAsed elevation – here in thailand not soo important, we have very less pressure change – but in northern europa with the high and low pressure – just like Chris wrote: up to 200 m difference,
    and what about Garmin – didn’t they think about someone traveling with bike 10 hours and getting full of the weather change ?

    I have mainly the problem want to be sure telling accurate climbing meter including the smal waves between also – no only netto from down to top …

    Thomas

    • The first Garmin GPS I ever owned, a “GPS III Plus”, included GPS based elevation. I am greatly distressed that the screen gave out recently and so far I haven’t been able to find a comparable unit. I have found barometric altimeters impractical for automobiles. For people who cannot handle the higher elevations it’s important to know at what elevation you’re about to pitch your tent or park your RV. My partner can handle several hours over 6000 or so feet and a continuous and promptly changing elevation reading is almost indispensable driving around in the western mountains. If you know of an auto mounting GPS navigator with gps based elevation, I’d be very pleased to hear of it.

  7. Looking to buy a GPS unit that will track me while I ski. Several companies have software that you can use to see what you did that day. It seems like the foretrex is the best unit for me. (If not please correct). Do I need to get the 401? If I get the 301 will the accuracy be too much of an issue?

    Thank you

    • Yes, the Foretrex will work for that, assuming you just want to be able to download the tracks when done and see where you’ve been. If you’re looking for something that will transmit your location to others, no, it won’t do that.

      The 401 has a barometric altimeter, which will give you somewhat more accurate elevation readings. Otherwise the 301 would work and should be just as accurate for lat/long positioning. The eTrex 10 is even cheaper.

  8. Having one that will show the barometric history is really nice when you’re hiking or backpacking. But they tend to be power hungry…

  9. I don’t currently have a GPS with barometric pressure information. If I did it would be more to see what the weather is doing, rapidly falling pressure? Better head for cover. I used to fly and and your altimeter was set to local Barometric pressure under 18kft. Every time you were handed off to a new controller or center they gave you the current pressure for where you were and you adjusted your altimeter to that pressure to make sure you knew if you were above or below your assigned altitude. Flying from Sacramento over the Sierras to a local airport was less than an hour but the local airfield was not at the elevation my altimeter thought it was, I was about 300′ lower than the traffic pattern. Now they have automatic reporting and give the pressure at the airport. So not having a gps with that feature I can’t say it’s the gps but pressure does change with weather, or vice versa.

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