Choosing a map projection

When choosing a projection in which to store your database, consider the database's primary use.

• Databases created under contract or to be used by a government organization are often in a projection determined by the governing body, such as state plane in the United States or Great Britain National Grid in the United Kingdom.
• Use equal area projections for thematic or distribution maps.
• Presentation maps are usually conformal projections, although compromise and equal area projections can also be used.
• Navigational maps are usually Mercator, true direction, and/or equidistant.

Other considerations for map projection choice

• The extent of the area to be mapped. Is it a database of the world, a continent, or a state?
• Location of the area to be mapped. Is it a polar, midlatitude, or equatorial region?
• Predominant extent of the area to be mapped. Is the area roughly circular or longer in the east–west, north–south, or some oblique direction?

The list below shows a range of choices for common map types.

World projections

Conformal	Mercator, Transverse, Oblique Mercator
Equal Area	Cylindrical, Eckert IV, Eckert VI, Mollweide, Flat Polar Quartic, Sinusoidal
Equidistant	Azimuthal
Straight Rhumb Lines	Mercator
Compromise	Miller, Robinson

World projections

Hemisphere projections

Conformal	Stereographic, Polar
Equal Area	Lambert Azimuth
Equidistant	Azimuthal
Global Look	Orthographic

Hemisphere projections

Continent or smaller region projections

Predominantly east–west along equator

Conformal	Mercator
Equal Area	Cylindrical

Continent or smaller region projections: Predominantly east–west along equator

Predominantly east–west away from equator

Conformal	Lambert
Equal Area	Albers

Continent or smaller region projections: Predominantly east–west away from equator

Predominantly north–south

Conformal

Transverse, UTM

Continent or smaller region projections: Predominantly north–south

Predominantly oblique

Conformal

Oblique Mercator

Continent or smaller region projection: Predominantly oblique

Equal extent in all directions

Conformal	Polar, Stereographic, UPS
Equal Area	Lambert Azimuth
Straight Great-Circle Routes	Gnomonic

Continent or smaller region projections: Equal extent in all directions

Correct scale

Between Points	Two-Point Equidistant
Along Meridians	Azimuthal (polar aspect), Equidistant, Equirectangular, Simple Conic
Along Parallels	Polyconic, Sinusoidal, Bonne

Continent or smaller region projections: Correct scale

These tables are based on Snyder, John P., 1987, Map Projections, A Working Manual, U.S. Geological Survey Professional Paper 1395, 385p.http://pubs.er.usgs.gov/publication/pp1395