Watched a program on TV where a professor demonstrated stereoscopic olfactory ability. A person was blindfolded and knelt on a grassy area where an invisible smell trail was laid out. The person was able to track the trail because of this ability.

The key part is your sinus cavity slightly closes one nostril creating a differential air flow. This difference allows us to figure out the direction the smell via the difference in intensity between nostrils which our brain uses to sense direction.