Map Projections | Class 11 Geography Notes

Conical Projection with one Standard Parallel

A conical projection is created by projecting the graticule of the globe onto a cone that touches the globe along a single parallel of latitude called the standard parallel. This standard parallel is the latitude where the cone is tangent to the globe, and distortion is minimal along this line. Parallels appear as arcs of concentric circles, and meridians are straight lines converging at the pole. The scale is true along the standard parallel and along meridians but is exaggerated away from the standard parallel. This projection is neither equal area nor orthomorphic but is useful for mapping mid-latitude regions with limited latitudinal extent and larger longitudinal extent.

Example: Construct a conical projection with one standard parallel for an area bounded by 10°N to 70°N latitude and 10°E to 130°E longitude with a scale of 1:250,000,000 and 10° intervals.

Calculation:

• Radius of reduced earth R = 640,000,000 / 250,000,000 = 2.56 cm
• Standard parallel = 40°N
• Central meridian = 70°E

Construction steps include drawing a circle of radius 2.56 cm, marking angles at 10° intervals, extending tangents to form the cone sides, drawing arcs for parallels, and drawing straight meridians converging at the pole.

Properties: 1. Parallels are arcs of concentric circles, equally spaced. 2. Meridians are straight lines intersecting parallels at right angles. 3. Scale is true along meridians and the standard parallel. 4. Meridians converge towards the pole. 5. Scale distortion increases away from the standard parallel.

Limitations:

• Not suitable for world maps due to distortion in opposite hemisphere.
• Distortion near poles and equator is significant.

Uses:

• Suitable for mid-latitude regions with east-west extent.
• Used for mapping railways, roads, river valleys, and international boundaries in mid-latitudes.

📊 Diagram: Figure 4.3 Simple Conical Projection with one standard parallel

🧪 Activity: Construct graticule for an area between 30°N to 70°N and 40°E to 30°W on a simple conical projection with one standard parallel at 10° intervals and scale 1:200,000,000.

🔗 Connection: Leads to study of cylindrical equal area projection, another important projection type.