Question

how can you say contour lines and mean sea level are use full to us?​

Answer 1

Explanation:

Contour line,is  a line on a map representing an imaginary line on the land surface, all points of which are at the same elevation above a datum plane, usually mean sea level.

                                      Imagine a land surface inundated by the sea to a depth of 100 feet (30.5 metres)—that is, the intersection of a horizontal plain with the uneven surface of the land. If then a line representing the edge of the sea is drawn on a map of the area, the result would be a contour line, and it would be called the 100-foot contour. Similar contours could be drawn at successive 100-foot intervals or at any desired interval.  

I think this might help you

Answer 2

Answer:

Contour line,is a line on a map representing an imaginary line on the land surface, all points of which are at the same elevation above a datum plane, usually mean sea level.