The contour lines

The contour lines

Contour lines are lines connecting points having the same height from a datum / field reference. The concept of contour lines can be easily understood by imagining a pool of water. If the water in a state of calm, then the edge of the surface water shows a line that has the same height and the line will close at the edge of the pond to form contour lines.
If the water level falls, for example the water level down 5 meters, then the edge of the water surface will form the second contour line. So then every surface water will form a line down the other contour (figure 10.1.1.)

Figure 10.1.2 shows the contour line drawing and image slices of the island. Tide line on the left is shown with contour lines that have a height of zero, if the water level rises every l0cm at a certain distance, then the edge surface of the water on the soil surface will form a contour line which has a height of 10 m, 20 m, 30 m and 40 m .

 

The slope of the land
The height between contour lines are sequentially called vertical hose or hose contours and its magnitude always remains on the map. At the intersection of the vertical interval is shown by the line AB. Horizontal distance between two contours is described by the distance BC. The distance is called the horizontal distance.
The slope of the land surface between points A and C are:

slope AB / BC = Hose Vertical / Horizontal Distance

Because the vertical interval is the amount that remains on the slope of each map, it will change if the horizontal distance changes.
Example:

The slope along the AC = 10/100 = 1 / 10 = 1:10

source : http://www.ilmusipil.com/garis-kontur-adalah