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

[Ron Frazier (ALE)]

I don't think Cumming has an airport, but I'll keep it in mind.

I took the GPS out with me to supper.  When I left, my house was at 1210 feet above sea level.  By the time I got back, it had sunk (on the display) to 1170 feet.  In the last 20 minutes of me sitting here, it has raised back up to 1185 feet.

So, I guess I cannot expect too much from the elevation function of this device.

Sincerely,

Ron


Pete Hardie <pete.hardie at gmail.com> wrote:

>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
>>
>> ______________________________**_________________
>> Ale mailing list
>> Ale at ale.org
>>
>http://mail.ale.org/mailman/**listinfo/ale<http://mail.ale.org/mailman/listinfo/ale>
>> See JOBS, ANNOUNCE and SCHOOLS lists at
>>
>http://mail.ale.org/mailman/**listinfo<http://mail.ale.org/mailman/listinfo>
>>
>
>
>------------------------------------------------------------------------
>
>_______________________________________________
>Ale mailing list
>Ale at ale.org
>http://mail.ale.org/mailman/listinfo/ale
>See JOBS, ANNOUNCE and SCHOOLS lists at
>http://mail.ale.org/mailman/listinfo


--

Sent from my Android Acer A500 tablet with bluetooth keyboard and K-9 Mail.
Please excuse my potential brevity if I'm typing on the touch screen.

(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