Understanding Map Projections
Understanding Map Projections
Understanding Map Projections
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GALL’S STEREOGRAPHIC<br />
Area<br />
Area is true at latitudes 45° N and S. Distortion<br />
slowly increases away from these latitudes and<br />
becomes severe at the poles.<br />
Direction<br />
Locally correct at latitudes 45° N and S. Generally<br />
distorted elsewhere.<br />
The central meridian is 176° E.<br />
DESCRIPTION<br />
Gall’s Stereographic was designed around 1855. It is<br />
a cylindrical projection with two standard parallels at<br />
latitudes 45° N and S.<br />
Distance<br />
Scale is true in all directions along latitudes 45° N<br />
and S. Scale is constant along parallels and is<br />
symmetrical around the equator. Distances are<br />
compressed between latitudes 45° N and S and<br />
expanded beyond them.<br />
LIMITATIONS<br />
Used only for world maps.<br />
USES AND APPLICATIONS<br />
Used for world maps in British atlases.<br />
PROJECTION METHOD<br />
Cylindrical stereographic projection based on two<br />
standard parallels at 45° N and S. The globe is<br />
projected perspectively onto a secant cylinder from<br />
the point on the equator opposite a given meridian.<br />
Meridians are equally spaced straight lines. Parallels<br />
are straight lines with spacing increasing away from<br />
the equator. Poles are straight lines.<br />
LINES OF CONTACT<br />
Two lines at 45° N and S.<br />
LINEAR GRATICULES<br />
All meridians and parallels.<br />
PROPERTIES<br />
Shape<br />
Shapes are true at latitudes 45° N and S. Distortion<br />
slowly increases away from these latitudes and<br />
becomes severe at the poles.<br />
56 • <strong>Understanding</strong> <strong>Map</strong> <strong>Projections</strong>