## Geocart Projections

What is a projection?

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ellipsoidal transverse Mercator

Gauss-Krüger

Gauss conformal

Gauss Hannover

transverse cylindric orthomorphic

Aspects of: Mercator

Parameters: Scale factor along central meridian

Classifications

Transverse aspect of Mercator projection
Cylindrical
Conformal

Graticule

Meridians and parallels: Central meridian, each meridian 90° from central meridian, and the Equator are straight lines. Other meridians and parallels are complex curves, concave toward the central meridian and the nearest pole, respectively.
Poles: Points along the central meridian
Symmetry: About any straight meridian or the Equator

Scale

True along the central meridian or along two straight lines on the map equidistant from and parallel to the central meridian
Constant along any straight line on the map parallel to the central meridian. (These lines are only approximately straight for the projection of the ellipsoid.) Increases with distance from the central meridian Becomes infinite 90° from the central meridian

Other features

Conceptually projected onto a cylinder wrapped around the globe tangent to the central meridian or secant along two small circles equidistant from the central meridian
Cannot be geometrically (or perspectively) projected
Rhumb lines generally are not straight lines.

Usage

Many of the topographic and planimetric map quadrangles throughout the world at scales of 1:24,000 to 1:250,000
Basis for Universal Transverse Mercator (UTM) grid and projection
Basis for State Plane Coordinate System in U.S. States having predominantly north-south extent
Recommended for conformal mapping of regions having predominantly north-south extent

Origin

Presented by Johann Heinrich Lambert (1728–1777) of Alsace in 1772. Formulas for ellipsoidal use developed by Carl Friedrich Gauss of Germany in 1822 and by L. Krüger of Germany, L.P. Lee of New Zealand, and others in the 20th century.

Other names

Gauss Conformal (ellipsoidal form only)
Gauss-Krüger (ellipsoidal form only)
Transverse Cylindrical Orthomorphic

Description adapted from J.P. Snyder and P.M. Voxland, An Album of Map Projections, U.S. Geological Survey Professional Paper 1453. United States Government Printing Office: 1989.