The human ear doesn't really have the ability to determine the height of a source reliably, only left/right. A better effect might be putting the audio out of phase on left/right, which usually has the effect of making it difficult to hear where the sound is coming from (it kind of makes it sound like it's omnidirectional like you mentioned)
For the recording, with the ground transmitter stationary, it could be separated by one receiver shilded to look at only the ground transmitter, and a second omni-directional one for anything flying.