[ale] WAY [OT] but geeky - how do I calibrate GPS barometric altimeter

[Pete Hardie]

Go down to the airport - it's a well-specified lat/lon and alt, and a
weather station.

Pete Hardie
--------
Better Living Through Bitmaps


On Mon, Feb 25, 2013 at 5:53 PM, Ron Frazier (ALE) <
atllinuxenthinfo at techstarship.com> wrote:

> Hi all,
>
> I just got my hands on a neat Garmin Etrex Vista H handheld GPS on
> clearance for hiking trails and such.  It has a barometric altimeter that I
> wish to calibrate.  I have to either enter an accurate known  barometric
> pressure; or I have to enter an accurate known elevation.
>
> I've checked Weatherbug (for Cumming, GA), The Weather Channel, and the
> Firefox ForecastFox plugin.
>
> The barometric pressure readings are: 29.85, 29.92, and 29.90.  As I
> understand it, these variations would be enough to create altimeter reading
> differences of around 70 feet.
>
> I can't necessarily use my weather station as a good barometric pressure
> gauge, since it depends on elevation.  (I usually calibrate that instrument
> by putting in the barometric pressure from The Weather Channel.)
>
> I don't know the exact elevation of my house, nor the exact elevation at
> the trail at the park.
>
> I can calibrate to GPS elevation, but that's not very accurate.
>
> Garmin says the altimeter is accurate to 10 feet if properly calibrated.
>  Of course, it will change with the weather.
>
> So, how can I determine accurate barometric pressure for a location, or
> accurate elevation, so I can calibrate this thing?  Is there a way to get
> elevation from google maps, or something?
>
> Note, this is not critical, not life threatening if I don't find the
> answer, not even exceedingly important.  But, I just want to get the most
> usage out of the device that I can.  And, you guys are a great source of
> geeky information of all sorts.
>
> Any help, as always, is appreciated.
>
> Sincerely,
>
> Ron
>
>
> --
>
> (PS - If you email me and don't get a quick response, you might want to
> call on the phone.  I get about 300 emails per day from alternate energy
> mailing lists and such.  I don't always see new email messages very
> quickly.)
>
> Ron Frazier
> 770-205-9422 (O)   Leave a message.
> linuxdude AT techstarship.com
>
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