When we use PhotoModeler to measure objects up to perhaps 1000 meters in size, our camera positions are close enough to the object to make the light ray distortion by the air negligible. In aerial photography the object being measured might be very far away and air caused distortion can have a significant effect. In astronomy, objects are viewed through the whole depth of the Earth's atmosphere and sophisticated techniques are needed to model the effects of air turbulence and other air effects.