Classification of Map Projection| Class 11 Geography

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Classification of Map Projection| Class 11 Geography

Classification of Map Projections

Map projections can be classified based on various criteria, including the mathematical method used, the properties preserved, and the type of projection surface. In the context of Class 11 Geography NCERT books, map projections are often categorized as follows:

1. Drawing Techniques

2. Developable Surface

3. Global Properties

4. Source of Light

Drawing Techniques

On the basis of method of construction, projections are divided into perspective, non-perspective and conventional or mathematical

Perspective Projections: These projections are created by projecting the image of a network of parallels and meridians from a globe onto a developable surface using a source of light. This method simulates how light projects shadows and images in real life.

Non-Perspective Projections: Unlike perspective projections, non-perspective projections do not require a source of light or casting shadows. They are developed without the aid of a light source and can be flattened onto surfaces.

Mathematical or Conventional Projections: These projections are derived using mathematical computation and formulae. They have little direct relation with the projected image and are based on mathematical principles rather than visual simulation.

Developable Surface

Map projections are categorized based on the nature of the surface onto which the Earth’s features are projected. These classifications help understand how different types of projections are created. On the basis of nature of developable surface, the projections are classified as cylindrical, conical and zenithal projections.

Cylindrical Projections: These projections are created using a cylindrical developable surface. A paper-made cylinder is wrapped around the globe, and the parallels and meridians are projected onto it. When the cylinder is cut open and laid flat, it provides a cylindrical projection on a plane sheet.

Conical Projections: Conical projections are drawn by wrapping a cone around the globe, and the shadow of the graticule network is projected onto it. When the cone is cut open and laid flat, a projection is obtained on a flat sheet.

Zenithal Projections: Zenithal projections are directly obtained on a plane surface when the plane touches the globe at a point, and the graticule is projected onto it. Typically, the plane touches the globe at one of the poles. Zenithal projections are further subdivided into normal, oblique, or polar based on the position of the plane touching the globe.

Global Properties

Map projections aim to preserve certain global properties such as area, shape, direction, and distances. However, it is challenging to maintain all these properties simultaneously in a single projection. Therefore, different types of projections are categorized based on the specific global property they prioritize.

Equal Area Projection (Homolographic Projection): This projection accurately represents the areas of various parts of the Earth. It ensures that the sizes of regions are correctly depicted, prioritizing equal area representation over other properties.

Orthomorphic or True-Shape Projection: In this projection, the shapes of different areas are portrayed correctly. It aims to maintain the true shape of geographical features, although this may come at the expense of area accuracy.

Azimuthal or True-Bearing Projection: This projection accurately represents the direction of all points from the center. It ensures that directional bearings are correctly depicted, providing valuable information for navigation and spatial analysis.

Equi-distant or True Scale Projection: In this projection, the distance or scale is correctly maintained. However, it’s important to note that maintaining scale accuracy throughout the entire map is challenging. Scale accuracy can only be achieved along specific parallels and meridians as needed for particular applications.

Source of Light

Map projections can also be classified based on the location of the source of light used in the projection process. Here are the main types of projections categorized according to the placement of the light source:

Gnomonic Projection: This projection is obtained by placing the light source at the center of the globe. It results in a map where great circles appear as straight lines. Gnomonic projections are often used in navigation and for depicting great circle routes.

Stereographic Projection: In stereographic projection, the light source is positioned at the periphery of the globe specifically at a point diametrically opposite to where the plane surface touches the globe. This projection is characterized by the fact that circles on the globe are transformed into circles on the plane, except for the equator which becomes a straight line.

Orthographic Projection: Orthographic projection is created with the light source placed at infinity from the globe, opposite to the point where the plane surface touches the globe. This results in a map where parallel lines of latitude and meridians of longitude appear as straight lines and the projection preserves the shapes of small areas well.

FAQs on Class 11 Geography Classification of Map Projection

What is map projection, and why is it necessary?

Map projection is the method of transferring the spherical surface of the Earth onto a flat map. It is necessary because it allows us to accurately represent the Earth’s surface for various purposes like navigation, planning, and analysis.

How are map projections classified based on drawing techniques?

Map projections are classified into perspective, non-perspective, and conventional or mathematical projections. Perspective projections involve the use of a light source to project the image of the Earth’s network of parallels and meridians. Non-perspective projections are developed without a light source, and conventional projections are derived through mathematical computation.

What are developable and non-developable surfaces in map projection?

Developable surfaces are those that can be flattened without distortion, such as cylinders, cones, and planes. Non-developable surfaces, like the Earth’s surface, cannot be flattened without distortion.

How are map projections classified based on the nature of the developable surface?

Map projections are classified into cylindrical, conical, and zenithal projections based on the nature of the developable surface used. Cylindrical projections are created using a cylindrical surface, conical projections use a conical surface, and zenithal projections are directly obtained on a plane surface.

What are the different types of projections based on global properties?

Projections based on global properties include equal area, orthomorphic (true-shape), azimuthal (true-bearing), and equidistant projections. Each type of projection aims to preserve specific properties like area, shape, direction, or scale.