move a UIImageView "up"

hi,
have uiimageview representing level of "artificial horizon" in plane. blue sky, brown ground. image clipped super view creates square.



when i move nose of plane up, move image down:



when move nose of plane down, move picture :



called "pitch"

far i've been modifying x axis of image:

code:

 imagehorizon.center = cgpointmake(imagehorizon.center.x, imagehorizon.center.y + valuetomove); 

when "roll" plane rotate picture either left or right:

code:

 imagehorizon.transform = cgaffinetransformrotate(imagehorizon.transform, angletorotate*(cgfloat)(m_pi/180)); 

now, problem once rotated picture , want modify "pitch", dont know formula use find correct x,y move picture towards sky or ground direction:



in other words, when rotate picture angle β, x, y value add center of image move on red line ?

help,
tex

 

maybe : http://forum.onlineconversion.com/showthread.php?t=5408

know have seen better tutorial on this, can't find anymore, sorry.

 

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