Gall's Stereographic

Description

Gall's stereographic was designed around 1855. It is a cylindrical projection with two standard parallels at latitudes 45° N and S.

Projection method

A cylindrical stereographic projection based on two standard parallels at 45° N and S. The globe is projected perspectively onto a secant cylinder from the point on the equator opposite a given meridian. Meridians are equally spaced straight lines. Parallels are straight lines with spacing increasing away from the equator. Poles are straight lines.

Lines of contact

Two lines at 45° N and S.

Linear graticules

All meridians and parallels.

Properties

Shape

Shapes are true at latitudes 45° N and S. Distortion slowly increases away from these latitudes and becomes severe at the poles.

Area

Area is true at latitudes 45° N and S. Distortion slowly increases away from these latitudes and becomes severe at the poles.

Direction

Locally correct at latitudes 45° N and S. Generally distorted elsewhere.

Distance

Scale is true in all directions along latitudes 45° N and S. Scale is constant along parallels and is symmetrical around the equator. Distances are compressed between latitudes 45° N and S and expanded beyond them.

Limitations

Used only for world maps.

Uses and applications

Used for world maps in British atlases.

Parameters

Desktop

• False Easting
• False Northing
• Central Meridian

Note:

Supported on spheres only.

Workstation

• Longitude of Central Meridian

Note:

Supported on spheres only.