Calculating Strike through compass in iphone

i am developing and application for geol开发者_开发技巧ogy and need to calculate the dip and strike(dip direction). As i have found the way to calculate the dip but does not know how to calculate the strike. strike is calculate according to the compass direction.

This are usefull in measuring rockface. so anyone knows the way to calculate then please suggest some solution.

Thank you.

How do you mean "calculate the strike"? As you say, the Strike is a compass direction. As a student we would simply measure it - no calculation required. Typically it is taken as the compass bearing of the horizontal line in the plane that is being measured. We would usually explicitly state whether the downdip direction or use a standard. Eg. I'd use a clockwise standard - ie. downdip was 90 degrees clockwise of the given strike bearing.

I note that some US texts prefer to give the compass bearing of the down dip direction rather than the strike; and there's already an iPhone/iPad app that gives this info (although it is very unreliable - inertial problems I think).

So what do you mean by "calculate"? Perhaps you have a cliff face and you are trying to calculate it from that? That would be a case for 3d geometry - the exact formulae would depend on the situation in question.