Map Scale | Class 11 Geography Notes

Construction of the Graphical/Bar Scale

Constructing a graphical scale involves drawing a line or bar on the map that visually represents distances on the ground. For example, for a map with an R. F. of 1 : 50,000, 1 cm on the map equals 50,000 cm (or 0.5 km) on the ground. To construct a graphical scale of approximately 15 cm length, the ground distance represented is 7.5 km (50,000 × 15 / 100,000). Since 7.5 km is not a round number, a convenient round number such as 5 km is chosen for the scale. The length of the line representing 5 km is calculated as (15 × 5) / 7.5 = 10 cm. This 10 cm line is then divided into 5 equal parts, each representing 1 km. The leftmost division can be further subdivided into smaller units such as 100 metres for precision. This graphical scale allows users to measure distances directly on the map with ease and accuracy. Similar procedures apply when constructing scales in the English System, involving miles and furlongs, with appropriate unit conversions and divisions. When dividing unequal lines into equal parts, geometric methods using angled lines and intersections can be employed to ensure accuracy.

📊 Diagram: Figure 2.2; Table on page 6 (2×7); Table on page 6 (2×10); Figure 2.4 Drawing of equal divisions in a graphical scale

🧪 Activity: Construct graphical scales for given R. F. or Statement of Scale using Metric and English units.

🔗 Connection: Leads to exercises and problems applying scale concepts and graphical scale construction.

Table on page 6 (2×7)

Table on page 6 (2×10)