The effects depend on three four main factors: mass, density, velocity, impact area characteristics.

Surprisingly, the impact angle can vary quite a good amount without much difference in the effects or the ultimate outcome.

Generally, you start with the diameter and depth of the crater. Then you include peripheral information, such as crater ejecta (type, composition, effects), as well as similar characteristics of the crater and it's walls. Third, you search for pieces of the meteor itself, as that will give you clues as to it's density, as well as to it's potential size (ratio of meteor found vs other matter). Then you crunch the numbers and can determine it's mass and velocity.

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If I set the budget, we'd have Ares and more. Unfortunately, I don't set the budget, and Ares is just too expensive and too far out for us to accomplish our goals within the budget we were given.

If we halt the ISS, all versions of Ares, and transport Orion and Altair aboard DIRECTv3's Jupiter family of Shuttle-Derived Launch Vehicles, we just might make it back to the Moon by 2020.