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

[Robert Reese]

Hello Ron,

Monday, February 25, 2013, 5:53:02 PM, you wrote:

> 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?



As others have noted, finding a bench mark is one of the best ways to do it.  I calibrate mine whenever we visit a lighthouse, since each one of them has a marker, and quite frankly is usually so close to sea level that a "guesstimation" usually works well enough within a dozen feet or so.  You can also find those markers on the website - ironically you'll get the GPS coordinates for them - as well as other information.  Note that the benchmarks are on NOAA's website and not the USGS website.

To find benchmarks near you, go here: 
http://www.ngs.noaa.gov/cgi-bin/datasheet.prl

Choose DATASHEETS
Choose COUNTY
Choose your State
Choose your County, and the Data Type you want is VERTICAL.
Click "Get Marks"
Play with the settings if you don't get good results.

(I sent you to the top of the datasheet area, rather than directly into the county area because I wanted to show you other options besides DATASHEETS.)



By the way, the altimeter feature, for me, is useful for hiking, yes, but more more so for warning me of potential severe weather changes as you noticed.  Huge pressure drops over short periods of time will prompt me to get the heck back to safety, pronto.

One last thing: you mentioned WeatherBug.  You probably don't remember it, but WeatherBug was well-known spyware back in the day.  I haven't trusted them since; a leopard never changes its spots, so to speak.  Try wunderground.com.

Cheers,
Robert~