move a UIImageView "up"

- February 24, 2012

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