Has anyone compared the accuracy of a Garmin's altitude numbers with a real altimeter or known source for a location? I have used our Garmin and iPhone to measure the altitude of our property and the numbers seem to be very different.
I didn't expect anyone to notice that. My tires are usually at 0 AGL but of course that changes when you go over a bridge.
Or on a ferry.
Which raises the question - when in a tunnel, what is your AGL altitude ?
- Tom -
somewhere between Bayou St Louis and Pearlington, on Rt 90, it was -35 maybe even a bit more
My Garmin Oregon 550 has a barometric altimiter. But interestingly, you calibrate the barometer by setting the correct elevation at a known point.
My nuvi's which of course just use satellites to report elevation are usually within 50 or 60 feet of what the Oregon shows, but sometimes can be way off by several hundred feet.
When calibrating your 550, do you also need to input a baro input in inches of mercury or millibars? Like in current weather condition.
On the Oregon, you go to the calibration setting on the Altimeter menu. From there you can use either the known elevation or the known barometric pressure. I know the elevation at my home, so I usually calibrate that way before I leave home for a hiking or geocaching outing. I will then check to see what the Oregon shows for barometric pressure and compare it to the current weather conditions being reported for my city. It is usually within .01 inches of what is being reported for pressure. Today when I calibrated it was dead on.
For the current units. I don't get out into the woods any longer since I don't live in Maine anymore. (don't miss the snow)
Says it has an auto calibration for barometric altimeter in addition to the other inputs. Sounds like fun, some of the things it will do. True north or auto mag var for location setting . Enjoy it.
Nice stuff to ponder
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