In cartography, a contour line (often just called a “contour”) joins points of equal elevation (height) above a given level, such as mean sea level. A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

The purpose of contour drawing is to emphasize the mass and volume of the subject rather than the detail; the focus is on the outlined shape of the subject and not the minor details.

Contour line, 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.

How to Draw Contour Lines in Art

1. Step 1: Choose What You’ll Draw and Gather Materials. For your first contour drawing, we recommend choosing just one object to draw, as this will be easier to focus on than several objects.
2. Step 2: Look at the Object.
3. Step 3: Draw Long, Continuous Lines.
4. Step 4: Go Slow and Steady.

Contour lines don’t cross because each line represents a particular elevation. If two contour lines crossed, the place where they intersect would have two different elevations, and this simply isn’t possible. However, contour lines can come very close to touching, especially in steep mountainous regions.

: the vertical distance between the elevations represented by adjacent contour lines on a map.

Divide the difference in elevation between the index lines by the number of contour lines from one index line to the next. In the example above, the distance 200 is divided by the number of lines, 5. The contour interval is equal to 200 / 5 = 40, or 40-unit contour intervals.

FACTORS FOR DECIDING CONTOUR INTERVAL

• 1) Scale of the map. The contour interval is kept inversely proportional to the scale of the map.
• 2) Purpose of the map. The contour interval on a map also depends upon the purpose for which the map is to be utilized.
• 3) Nature of the ground.
• 4) Availability of time and funds.

Factors Affecting the Selection of Contour Interval

Contour interval (CI) is the difference of value of two consecutive contours (larger contour value – next smaller contour value). Horizontal equivalent is the horizontal distance between any two consecutive contours. Generally CI remains constant for any contour map, but horizontal equivalent varies with varying slope.

The contour interval depends upon the general topography of the terrain. In flat ground, contours at small intervals are surveyed to depict the general slope of the ground whereas high hills can only be depicted with contours at larger contour interval.

If the higher values are inside the bend or loop in the contour, it indicates a Ridge. 9. Contour lines never run into one another except in the case of a vertical cliff. In this case, several contours coincide and the horizontal equivalent becomes zero.

Contour lines on a slope are generally straight and parallel to each other. If four people walked away from each other on a slope, one person would go downhil, one would climb, and two would stay at the same elevation. 3) Summit (peak) – the highest point in a given area.

Uses of contours maps

• Uses of contours maps. Contours provide valuable information about the nature of terrain.
• Nature of Ground. To visualize the nature of ground along a cross section of interest,
• To Locate Route.
• Intervisibility between Stations.
• To Determine Catchment Area or Drainage Area.
• Storage capacity of a Reservoir.

1 : an outline especially of a curving or irregular figure : shape the sleek contours of the car The map shows the contour of the coastline. also : the line representing this outline. 2 : the general form or structure of something : characteristic —often used in plural the contours of a melody…

2 methods

Direct method of contouring is cheaper than indirect method….Explanation:

Contour surveying. Interpolation of contour. Interpolation of the contours is the process of spacing the contours proportionately between the plotted ground points established by indirect methods. The methods of interpolation are based on the assumption that the slope of ground between the two points is uniform.

Methods of Contouring Radial Line Method or Tachometric Method • In this method, a number of radial lines are set out at known angular interval (i.e. 15 0 or 30 0) at each station. The point are selected on a line depend on the nature of the ground surface. Instead of the level, a tachometer may be used.

Indirect Method: This method of contouring is also known as contouring by spot levels. This method is commonly employed in all kinds of surveys as this is cheaper, quicker and less tedious as compared with the direct method.

Tacheometric method

Contour farming is farming with row patterns that run nearly level around the hill — not up and down the hill. Contour stripcropping is crop rotation and contouring combined in equal-width strips of corn or soybeans planted on the contour and alternated with strips of oats, grasses, or legumes.

Therefore, contour farming alone is not sufficient to control erosion on steep, long slopes, erodible soils, and during erosive rains. The major drawbacks of contour farming are frequent turning involving extra labor and machinery time, and loss of some area that may have to be put out of production.

Contour ploughing mitigates the impacts of floods, storms and landslides on the crops by reducing soil erosion up to 50 percent, controlling runoff water, increasing moisture infiltration and retention and thus enhancing soil quality and composition.

The advantages of contouring are: the velocity of runoff is checked; the adsorption of rainfall is increased; erosion is reduced by slowing the rate of runoff; and, temporarily storing runoff behind contour ridges increases infiltration and collects sediment.