Also, camera operators are not as accustomed to maintaining a strict lower frame line as they are at watching their headroom, so the mic tends to pop into the shot more frequently. Another important consideration when booming is not just the angle of the mic but the distance. One of the great advantages of using the mic on a fishpole, as opposed to being attached atop a camera, is that the mic can be brought close to the subject even when the camera isn't. Every inch closer that the mic can be to the subject will improve the quality of the sound. Never fly the mic higher than it absolutely needs to be if you want to control echo and background noise.
Some camera operators confuse width with height.
In other words, the back of the mic does not offer the most rejection to background noise. The most rejection occurs around four o'clock and eight o'clock respectively. So to decrease a source of noise, you would not want the mic facing directly away from it, as that would only serve to put the noise at the live spot in the back. Instead, angle the mic so that the noise source strikes slightly to the side and rear. When deploying your mic overhead, keep these angles in mind.