# Planar Projections: Azimuth Equidistant and Stereographic (Especially for GATE-Geospatial 2022)

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Planar projections are the subset of 3D graphical projections constructed by linearly mapping points in three-dimensional space to points on a two-dimensional projection plane. There are many map projections are commonly used.

## 1. Azimuth Equidistant

### Properties

Equally spaced straight lines intersecting at a central pole. The angles between them are true angles.

Equally space circles, centered on the central pole. The entire earth may be shown.

Central pole is a point. The opposite pole is a bounding circle with a radius twice that of the equator.

### Major Uses

Air and sea navigation charts; equatorial and polar area large-scale maps.

## 2. Stereographic

### Properties

Map projection is conformal. Map is infinite in extent with outer hemisphere inflating severely, so it is often used as two hemispheres.

Maps all small circles to circles, which is useful for universal mapping to preserve to shapes of holes.