Overview of Scales

• Importance of Scale – Scale helps to represent the earth or any area correctly on a map and shows accurate distances. Without scale, a map is only a rough sketch.
• Three Types of Scale – Scale is expressed in three ways:
  1. Statement of Scale
  2. Representative Fraction (R.F.)
  3. Linear (Graphical) Scale
• Statement of Scale – Expressed in words (e.g., 1 cm = 1 km). It is simple and easy to understand but may change if the map is enlarged or reduced.
• Representative Fraction (R.F.) – Expressed as a ratio (e.g., 1:100,000). It has no unit and is called an international or natural scale because it can be used anywhere.
• Limitation of R.F. – Distances cannot be directly measured from it, and it may not remain correct if the map is resized.
• Linear Scale – A straight line divided into equal parts to measure distance directly from the map.
• Advantage of Linear Scale – It remains correct even if the map is enlarged or reduced, making it very practical for measuring distances.

• "Scale is the ration between the distance of any two points on the map and the actual distance of the same points on the ground".

\[\boxed{\mathrm{Scale}=\frac{\text{Map distance between two points}}{\text{Ground distance between the same points}}}\]

\[\boxed{\mathrm{R.F.}=\frac{\text{Map distance}}{\text{Ground distance}}}\]

• Basic Requirements – A graphical scale can be drawn when the Statement of Scale or R.F. is given. The length of the scale should generally be 12–20 cm (or 5–8 inches).
• Use of Round Figures – Distances shown on the scale must be in round figures like 10, 50, 100, 500, 1000, etc.
• Primary Divisions – The whole line of the scale is divided into equal primary divisions showing major distances.
• Secondary Divisions – The first primary division on the left is further divided into smaller parts to show shorter distances. Zero (0) is written between primary and secondary divisions.
• Division of Line – A straight line can be divided into equal parts by drawing an inclined line and marking equal distances on it, then joining them with parallel lines.