LESSON 50

• 5 DIFFERENT TYPES OF CONTOUR DESIGNED BY CARTOGRAPHERS:

  INDEX

  INTERMEDIATE

  SUPPLEMENTAL

  DEPRESSION

  APPROXIMATE
• INDEX CONTOUR A contour is shown by a heavier line at regular intervals on a topographic map as convenience in scaling elevations, and to provide ease and speed in reading contours.
• These heavier lines which are normally twice the gauge of the standard contours are called the index contours
• INTERMEDIATE CONTOUR The four lighter weight contours found between the index contours.
• SUPPLEMENTAL CONTOUR Certain portions of the map area sometimes are so flat or level that the contours are too far apart to show properly important breaks in the terrain. To better depict the relief and remedy such situations, supplemental or auxiliary contours are used.
• DEPRESSION CONTOURS drawn to show low spots such as excavation around which contours close. The symbol used is the index or intermediate contour to which ticks are drawn perpendicular to the contour line on the downhill side.
• APPROXIMATE CONTOUR To portray reasonable idea of relative elevations, the map maker has to make an educated guess rather than have a blank area in the map
• CONTOUR INTERVAL the constant vertical distance between two adjacent contour lines
• SELECTION OF CONTOUR INTERVALS:

  RELATIVE COST

  PURPOSE OF THE MAP

  NATURE OF THE TERRAIN

  SCALE OF MAP
• CHARACTERISTICS OF CONTOURS:

  AI4C