In language we pin down the consonants, which are really absences of sound. Many writing systems, from Sanskrit to Arabic, write only the consonants. The majority of meaning is carried by the chords of vowel formants, which are shaped by the mostly absent consonants. Consonants are moments when the formant vector changes its direction.
In traveling we pin down the landmarks, which are really absences of travel. We tell people to turn left at the blue house, or turn right at the corner of 4th. Landmarks are places where the travel vector changes its direction.
Polistra's Mill 