I am trying to make a 3D model on the computer that is accurate from the unit.
What does this mean? You want to produce a 3D image showing what the hardware looks like? You want to use the hybrid device as a 3D drawing device? Something else?
I think he means that he wants to be able to get an extremely accurate, where exactly am I pointing, and how fast am I accelerating (which could be turned into how fast am I going) readout for a computer. That combined with accurate GPS coordinates would then be good for tracking whats going on with something.
Why you didn't get a 3 Axis compass though is a little beyond me, because then there wouldn't be much requirement for programming your own compensation. And they're really cheap (actually most single axis or dual axis units are more expensive, though they may be more accurate)
But so when you say you want to compensate it for tilting. What degree of tilt compensation you want. Cause if you tilt the thing more then 10 degrees your numbers are going to be quite a bit off regularly, and anywhere past 45 degrees of tilt, and your practically going to be making up your direction out of gyro data.
Edit. Actually quick thing, make it a bit easier for us. Which sensors do you have exactly?