Originally Posted by
ElNull
My question here was not how an IRS do alignment. My question was that why not an IRS just take all the position from the GPS rather than taking time sensing and calculating.
As pointed out, it's so the box knows where true north is, and at what latitude it is currently parked.
The whole point of an inertial system is it can work without a gps input, they have been around since long before GPS was invented.
The answer was, it can't figure out the earth's rotation from gps alone. Gps satellites are mainly geo stationary , they stay in same place relative to earth's surface, and therefore GPS signal cant be used to sense earth's rotation. What the GPS is good for, is an initial latitude and longitude position.
Ttfn