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Ron,

Try adding in some cross controll input & acelerometer error Bzzzzt. The
deal is that over time, any acelerometer, even 3 axix will accumulate
error, and ignoring your idea of non-realtime GPS directional input for
the moment, what you need is a leaky integrator. To accomplish this, you
need to be able to sense the horizon in an accelerated frame of
reference. You can accomplish this in a number of ways. The two that
come readily to mind are magnetometers & solid state or otherwise steam
gage type gyros. Sadly, this last requirement for instrumentation is
often where the expense for your system will come in to play.

Evan Carew

Ron Webb wrote:
Your GPS can't tell you whether you're straight and level, only whether
you're straight.


Agreed.

But if the GPS says I'm straight (over a 10 second average) and the
accelerometer says the roll axis vector is pointed toward the floor of the
aircraft, then it seems to me I'm straight (otherwise the heading would be
changing) and level - since if there is no heading change the only vector
remaining is G.



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