Conic Projections and Types: Albers Equal Area, Equidistance Conic, Lambert Conformal Conic, & Polyconic (Especially for GATE-Geospatial 2022)

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In flattened form a conic projection produces a roughly semicircular map with the area below the apex of the cone at its center. When the central point is either or Earthีšs poles, parallels appear as concentric arcs and meridians as straight lines radiating from the center.

There are many map projections are commonly used:

1. Albers Equal Area

This Figure Shows Albers Equal Area

Properties

Shape is true along the standard parallels of the normal aspect, or the standard lines of the transverse and oblique aspects.

There are no area distortions on any of the projections.

Local angles are correct along standard parallels or standard lines. Direction is distorted elsewhere.

Major uses โ€“ Small regional and national maps

2. Equidistance Conic

This Figure Shows Equidistance Conic

Properties

Equally spaced straight lines converting to a common point, usually beyond the pole.

The angles between the meridians are less than the true angles.

Equally spaced concentric circular arcs centered on the point of meridians convergencs.

Major uses: Region mapping of midlatitude area with east-west extent; atlas maps for small countries.

3. Lambert Conformal Conic

This Figure Shows Lambert Conformal Conic

Properties

It is a conformal conical projection with two reference parallels secant lines which help to minimizes distortion; in fact, there is no distortion along the standard parallels but distortion increases further from the chosen parallel.

Major uses: Navigation charts; U. S. State Plan Coordinates System for all east-west State Plane Zones; continental U. S. maps; Canadian maps.

4. Polyconic

This Figure Shows Polyconic Projection

Properties

Each parallel is a circular arc of true scale. The scale is also true on the central meridian of the projection.

Major uses: Topographic maps; USGS 7.5- and 15-min quadrangles

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