Originally Posted by
ElNull
this might be dumb question but at ground why the IRS would need to sense the earth rotation when it already have position from the GPS? Or is it just need it for a comparison?
Er, so it can work out your position.
To work out where you are, it does a mathematical calculation, based on your speed over the ground, and heading.
Ignoring ALL other factors , in simples terms your speed over the ground is going to be different if flying east to west or west to east, if flying at a constant air speed.
Ttfn