Lecture 4 How to read a topographic map

Introduction to Topographic Maps

  • Presentation by P. Hewage, Department of Social Sciences, Kotelawala Defence University.

  • Lecture date: 17.08.2022

Definition of Topographic Maps

  • Topographic Maps (also referred to as Topographical Maps)

    • Detailed illustrations of natural and man-made features on the ground.

    • Features include roads, railways, contours, elevations, rivers, lakes, and geographical names (Source: Canadian Centre for Topographic Information).

Features Depicted on Topographic Maps

  • Relief: Mountains, valleys, slopes, and depressions.

  • Hydrography: Lakes, rivers, streams, swamps, rapids, and falls.

  • Vegetation: Green spaces, agricultural areas, forests.

  • Transportation: Roads, trails, railways, bridges, airports, and seaplane anchorages.

  • Culture: Buildings, urban development, power lines, pipelines, and towers.

  • Boundaries: International, provincial, territorial, administrative.

  • Toponymy: Place names and names of water features and landforms.

Types of Topographic Maps Classified by Scale

  • Large-scale Maps: (1:24,000) - Ideal for urban and detailed rural areas.

  • Intermediate-scale Maps: (1:50,000 to 1:100,000) - Suitable for land management and planning.

  • Small-scale Maps: (1:250,000 and above) - Provide a more comprehensive view for regional planning.

Purpose of Topographic Maps

  • Represent features using symbols (streets, buildings, streams, vegetation).

  • Serve as a vital educational resource in science, geography, and history.

  • Ideal for various activities and applications in different geographical areas.

History of Topographic Maps

  • Giovanni Domenico Cassini: Initiated detailed mapping of France in the 1670s.

  • His family continued the work posthumously, resulting in the Carte de Cassini, published in 1793, recognized as the first accurate topographic map of a country.

Topographic Maps in Sri Lanka

  • Four types of maps published, including:

    • 1:63,360 Scale: Completed in 1924, revised in 1985.

    • 1:50,000 Scale: First edition started in 1985; revised in 1999.

    • 1:10,000 Scale: Complete coverage; published in 1992.

    • 1:250,000 Scale: Complied data from 1:50,000 maps.

Reading Topographic Maps

  • Features indicated as points, lines, and areas.

  • Area Features: Color-coded for vegetation (green), water (blue), and built-up regions (gray/red).

  • Line Features: Represented by various lines (e.g., contours in brown, streams in blue).

  • Point Features: Symbols for buildings, water tanks, schools, etc.

Contours on Topographic Maps

  • Contours indicate equal elevation; they don’t cross each other.

  • Contour Types: Index contours (wider), intermediate, and supplementary (narrower).

  • Close contour lines indicate steep slopes; widely spaced lines indicate gentle slopes.

  • Spot elevations are marked between contour lines.

Importance of Symbols and Peripheral Information

  • Labels and symbols indicate map features, including names of places and corresponding information.

  • Understanding symbols is crucial for reading and interpreting maps.

Conclusion

  • Topographic maps are essential tools for visualizing terrain and understanding spatial relationships in geographical areas.