hish747
Pre-takeoff checklist
I noticed this weekend that Stratus 2s altitude was off by about 200 feet. Has anyone else using the stratus had this problem? If so, is there a solution?
I noticed this weekend that Stratus 2s altitude was off by about 200 feet. Has anyone else using the stratus had this problem? If so, is there a solution?
GPS altitude is basd on a standard datum plane which is NOT sea level or the ground. I trust the altimeter, if its been checked & cert.
You don't just trust, it you *go by it*
... above a mathematical model ellipsoid that approximates the shape of the earth. IIRC most GPSs use WGS 84. The operative words here are "model" and "approximates."GPS altitude is true altitude ...
And there you have it folks. The pointlessly argumentative nature of POA captured in one line (again).
I'd put money on the stratus being accurate. My altimeter is always a little off in comparison. I've noticed when checking on flightaware that my recorded altitude is usually a little lower than what my altimeter read.
There really is a distinction. Barometric altimeters do make errors, even when properly adjusted, at nonstandard temperatures. They are systematics and are highly reproducible. The point is that everyone makes the same errors, so it doesn't matter, except for terrain avoidance. And terrain avoidance is done either visually or with large margins (though there are correction tables, and it can get significant when really, really cold).
The distinction is much more obvious in the flight levels, where the pressure is always presumed to be standard. You can make enough of a difference there using the GPS altitude to put you in an opposite-direction RVSM airway. Not good at all.
... above a mathematical model ellipsoid that approximates the shape of the earth. IIRC most GPSs use WGS 84. The operative words here are "model" and "approximates."