# Types of Projections Based on Development Surface (Conic, Cylindrical and Planar) (Especially for GATE-Geospatial 2022)

Get top class preparation for CBSE/Class-6 right from your home: get questions, notes, tests, video lectures and more- for all subjects of CBSE/Class-6.

Examrace Books on Mapping, GIS, and Remote Sensing prepares you throughly for a wide range of practical applications.

Maps are flat; some of the simplest projections are made onto geometric shapes that can be flattened without stretching their surface. These are called developable surfaces. Common examples are cones, cylinders, and planes.

The first step in projecting from one surface to another is creating one or more points of contact. Each contact is called a point of tangency. A planer projection is tangential to the globe at one point. Tangential cones and cylinders touch the globe along a line.

## Types of Projection Families Based on the Developable Surface

Projection families are based on the developable surface that is used to create them. Many common map projections are classified according to the projection surface used:

## Conic Surface (Tangent)

Earth intersects the cone at two circles. All points along both circles have no scale distortion.

A cone is placed over a globe. The cone and globe meet along a latitude line. This is the standard parallel. The cone is cut along the line of longitude that is opposite the central meridian and flattened into a plane.

## Cylindrical Surface

Earth intersects the cylinder on two small circles. All points along both circles have no scale distortion.

A cylinder is placed over a globe. The cylinder can touch the globe along a line of latitude (Normal case) , a line of longitude (Transverse case) , and another line (oblique case) .

## Planar Surface

Earth intersects the planer on a small circle. All points on circle have no scale distortion.

A polar is placed over a globe. The plane can touch the globe at the pole (Polar case) , the equator (Equatorial case) , or another line (Oblique case) .

## Polar Surface (Different Perspectives)

Azimuthal or planar projections can have different perspective points. The gnomonic projection՚s point is at the center of the globe. The opposite side of the globe from the point of contact is used for a stereographic projection. The perspective point for an orthographic projection is at infinity.