Topographical maps are essential for the study and measurement of various terrains. One of their defining features is the presence of contour lines, which represent the elevation levels of a landscape. The bottom of a topographic map shows the height interval between each contour line, the scale of the map and rulers representing various units of distance.
Topographic maps allow the calculation of the gradient of a terrain. This process requires taking the difference in height between two points and dividing by the distance between these points. For example, if the height difference between two points is 400 feet and the distance between these points is 2 miles, the gradient is 400 feet divided by 2 miles, or 200 feet per mile. One useful application of this formula is for calculating the flow of a river down a mountain.
Additionally, contour lines allow individuals to make judgments on construction locations for new buildings. For example, a person can determine the highest point a river has risen during a flood by observing the surrounding contour lines. This knowledge is useful for determining the need to purchase home flood insurance in a specific area. This also allows insurance companies to determine the risk factor of a home and to set the price accordingly.