It is used to determine locations of objects and can be used to calculate a 3-dimensional location when multiple sources are used.
The term RADAR is an acronym for RA dio D etection A nd R anging. It uses primarily microwave frequencies, although lower radio frequencies may also be used. Knowing the location of potential obstructions as well as a vessel's specific location with respect to fixed objects or other moving ones is indispensable to safe navigation at sea or in the air.
for further examples and general discussion of mechanisms.