Linewatch operations are conducted near international boundaries and coastlines in areas of Border Patrol jurisdiction to prevent the illegal entry and smuggling of aliens into the United States and to intercept those who do enter illegally before they can escape from border areas. Signcutting is the detection and the interpretation of any disturbances in natural terrain conditions that indicate the presence or passage of people, animals, or vehicles. The operation that's designed to detect changes in the natural environment, which may indicate passage of illegal aliens is called: