Vault/Fall Takeoff Angle Question

[MSI]

Q: From the crash forum:

• I am working on a crash where a Jeep ran off the road into a ditch and then went airborne after jumping a driveway. The entire scene is on a hill in that the landing area of the car is lower that where the takeoff occurred so I am treating it like a fall. In trying to determine the takeoff angle for use in estimating the speed at takeoff I can see that the vehicle had its driver's side tires on the shoulder (which would be a nearly level takeoff angle) and that the passenger side tires were in the ditch and much lower than the driver side tires (around a 20 degree takeoff angle going up to the driveway) meaning the Jeep was tilted around its y axis at takeoff. My question is how to determine the overall takeoff angle? Do I just go with the 20 degrees from the lower tires and negate the tires on the level surface or do I do something like take an average of the of the two (result would be around 10).
  
  In running rough numbers for the crash the difference between the results is pretty drastic with the level takeoff being much higher (80 MPH) vs if I just use the lower (around 30 MPH). My gut feeling from looking at the physical scene is that the jeep was going at least 50 mph at takeoff as it was only airborne for about 66 feet before rolling over several times.
  
  Any thoughts you have would be appreciated.