What is echo ranging? State any one application of this technique.

(N/A) Echo ranging is a technique used to determine the distance,direction,and speed of an object by measuring the time interval between the emission of a sound pulse (usually ultrasound) and the reception of its echo.
One application of this technique is in $SONAR$ ($Sound$ $Navigation$ $And$ $Ranging$),which is used to measure the depth of the sea or to locate underwater objects like hills,valleys,submarines,icebergs,and sunken ships.