हिंदी
CISCEISC (Arts) Class 12
प्रश्न पत्र३७२
पाठ्यपुस्तक उत्तर१६६८१
महत्वपूर्ण प्रश्न एवं उत्तर५८७१
अवधारणा स्पष्टीकरण और वीडियो९५३
समय सारणी१५
पाठ्यक्रम

Overview of Representation of Relief

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Estimated time: 15 minutes
CISCE: Class 12

Key Points: Methods of Showing Relief on Maps

  • Relief Representation – Maps are two-dimensional, so special methods are used to show three-dimensional landforms like mountains and valleys.
  • Colour Method – Different colours show different heights (e.g., green for plains, brown for hills, white for snow areas). It gives a quick overall view but may overlap.
  • Hachures – Short broken lines drawn along slopes. Close thick lines show steep slopes; thin, spaced lines show gentle slopes. They show shape but not exact height.
  • Spot Heights, Bench Marks & Trigonometrical Stations – These give exact height above sea level at specific points but do not show the full relief of an area.
  • Hill Shading – Slopes are shaded to show light and shadow effect. It gives a natural look but does not show exact heights clearly.
  • Layer Tints (Hypsometric Tints) – Different colour shades are used between contour lines to show height differences (blue for sea, green for lowlands, brown for highlands).
  • Contours – Imaginary lines joining places of equal height above sea level. They are the most accurate and commonly used method of showing relief.
CISCE: Class 12

Key Points: Vertical Interval and Horizontal Equivalent

  • Vertical Interval (V.I.) – It is the difference in height between two successive contour lines.
  • Unit of Measurement – V.I. is measured in metres or feet and remains constant on a given contour map.
  • Example of V.I. – If the vertical interval is 100 metres, contours will be drawn at 0, 100, 200, 300 metres, and so on.
  • Horizontal Equivalent (H.E.) – It is the horizontal distance between two successive contour lines.
  • Relation with Slope – H.E. is small on steep slopes (contours close together) and large on gentle slopes (contours far apart).
CISCE: Class 12

Key Points: Contours – Precautions, Interpolation & Profile

  • Precautions for Drawing Contours – Contours are continuous curved lines, drawn at a constant interval. They do not break and usually form closed curves.
  • Spacing of Contours – Contours are close together on steep slopes and far apart on gentle slopes. They generally do not cross each other (except in special cases like cliffs).
  • Interpolation of Contours – It is the method of drawing contour lines between known height points (spot heights, bench marks, etc.) using equal contour intervals.
  • Fixing Contour Interval – The contour interval is decided based on the range of elevation and is usually taken in round figures (10 m, 20 m, 50 m, 100 m, etc.).
  • Profile or Cross-Section – A cross-section is drawn from contours to show the vertical shape of the land along a line, helping to understand slopes and landforms clearly.
CISCE: Class 12

Key Points: Methods of Drawing a Profile

  • Two Methods – A profile (cross-section) can be drawn by:
    1. Drawing perpendiculars
    2. Using a paper strip
  • By Drawing Perpendiculars – A base line is drawn equal to the section line on the map. Perpendicular lines are erected and contour heights are marked according to the vertical interval.
  • Joining Points – After marking all heights, the points are joined smoothly to form the profile of the land.
  • Vertical Scale – The horizontal scale remains the same as the map, but the vertical scale may be slightly exaggerated (5–10 times) for clarity.
  • By Paper Strip Method – A paper strip is placed along the section line, contour points are marked, transferred to a graph with a suitable vertical scale, and then joined smoothly to complete the profile.
CISCE: Class 12

Key Points: Slopes & Relief by Contours

  • Steep slope – Contours close together.
  • Gentle slope – Contours far apart.
  • Uniform slope – Contours evenly spaced.
  • Concave & Convex slopes – Spacing changes from bottom to top.
  • Conical hill – Circular contours, height increases towards centre.
  • V-shaped valley – ‘V’ points upstream; Spur – ‘V’ points downhill.
  • Cliff/Waterfall – Contours very close or touching (very steep).
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