MnGCA

msteffel · Posted: Thu Apr 24, 2008 2:22 pm Post subject:

Sorry, I know I'm getting off the thermometer topic, but it kind migrated toward the accuracy of altitude in GPSs...

One attempt at a solution to getting an accurate altitude is motionbased's Gravity. http://wiki.motionbased.com/mb/Gravity It cross references the horizontal position (latitude/longitude) provided by the GPS with an elevation that has been acquired by professional survey.

Granted this is "after the fact" [it takes the .gpx file and goes from there] and cause it's following a survey it wont help if you were off the ground in a plane/helicopter/etc when you took the readings. But it supposedly more accurate, especially if your GPS doesn't have a Barometric Altimeter http://wiki.motionbased.com/mb/Barometric_Altimeter

Arcticabn · Posted: Thu Apr 24, 2008 3:16 pm Post subject:

Both of the last two posters are correct. My point is that even with the Csx if you turn off the barometer you can still get altitude off the sat fix. If you are interested in a baro altitude fix, you need to calibrate it that day and not turn it off. You have to calibrated it near the location you intend on being.
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spinowner · Posted: Thu Apr 24, 2008 8:41 pm Post subject:

And if you are in a changing weather pattern (in other words when the barometric pressure is rising or falling) you may need to calibrate more than once a day.
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