Seat belts and airbags were inserted into cars around the time of the late 1950s so the rate of death during a car accident would decrease because people are more likely to survive. And then in 1991 Side Impact Protection System (SIPS) was placed into cars again reducing fatalities during a car incident as people became more protected. :)
Answer:
To see land elevation or underground elevation.
Explanation:
You can use it to know what it under the ground before digging if you need a space to construct a building or parking. Or perhaps, even when building a house.
