Map Projections: Some Applications

Map Projections

Some Applications for Projections

Introduction

Frequently a proper choice of projection, scale, orientation and coordinates is crucial for a map to convey its message quickly and unequivocally, as demonstrated by a few examples.

When a reference is presented, the maps in this section are not scannings or reproductions but rather approximate reconstructions of the original sources (for instance, the original faunal regions map does not use an equal-area projection) for illustration purposes.

Faunal Regions and Global Connections

Major Faunal Regions of the World

	Neartic
	Palaearctic
	Ethiopian
	Neotropical
	Oriental
	Australasian
	Oceanic

Faunistic division of the world, modified Maurer projection

For zoological classification purposes, the world is divided in faunal regions.
Here (after Oliver L. Austin and Arthur Singer, Birds of the World, Hamlyn Publ. 1968), a map based on Maurer's star projection presents all lands minus Antarctica. Since climate is a great determinant of faunistic features, most regional borders follow latitudes and are, therefore, roughly concentric in polar-aspect maps.

A land arrangement similar to the previous starlike map is employed in the latest version of Buckminster Fuller's icosahedral projection. It was used for presenting fiber cable routes and intercontinental network traffic in Thomas B. Allen's The Future is Calling, National Geographic 200(6), December 2001. The projection choice was appropriate, since connections to Antarctica are negligible and no routing lines had to be broken, even across oceans.

Migration Paths

Human migration according to Out of Africa hypothesis

Possible migration of early human population, according to the "Out of Africa" hypothesis; clipped Mercator map, central meridian 150°E

According to the "Out of Africa" theory, modern man appeared as a single African species nearly 100000 years ago, then spread throughout the world (K.Wong, Is Out of Africa Going Out the Door?, Scientific American 281(2), August 1999). A simple coordinate rotation avoids cutting the migration path between Asia and Alaska.

Conjectured migration paths of early American/Asian populations

Present and fossil teeth suggest several migration waves in the past, when reduced sea levels created bridges between now isolated Japanese and Aleutian islands. Cassini projection.

Some particular migration paths relate populations in eastern Asia which may have later populated Polynesia, northern Asia and the Americas. Dental anthropology (Christy G. Turner II, Teeth and Prehistory in Asia, Scientific American 260 (2), February 1989) provides evidence depending on several genetic factors, not culturally acquired and seldom affected by the environment.

Orbital Tracks


Part of a great circle in an equidistant cylindrical projection	The same curve in an orthographic map

The crash of the Mir space station on the Pacific Ocean attracted a lot of attention. Most media coverage used cylindrical projections to depict the station's last moments following an apparently sinuous curve. Of course, the actual path of a low-orbit object looks much more simple when presented tridimensionally or as an azimuthal orthographic map:

Despite popular conceptions and illustrations, many satellites cruise at relatively low orbits, nearly grazing Earth's top atmosphere: a typical average altitude for Mir and the International Space Station is 390 km, while the Space Shuttle routinely performs orbits below 250 km (geostationary satellites ride much higher, at nearly 36000 km). The example is simplified, since orbiting objects neither follow exactly circular trajectories nor keep constant altitude; besides, the planet itself does not lie still but rotates beneath their paths.

The curve separating day/night areas is also roughly a great circle, thus the sinuous graphics in popular desktop programs displaying a "sun clock" on rectangular maps.

Heavenly Maps

For most of mankind history, stars and planets were mainly an aid for navigation and time reckoning. In this role, it is perfectly appropriate thinking of heavenly bodies as attached to an enormous spherical shell slowly rotating around Earth. Such an sphere can be mapped by exactly the same processes as used for ordinary maps. In fact, some map projections were first used by early astronomers for charting the stars instead of lands.


Sky in boreal hemisphere	Sky in austral hemisphere sky

Two polar azimuthal stereographic maps present the night sky as seen in the north and south poles. Viewers in other latitudes and dates will see the constellations more or less tilted.
In the boreal (northern) sky map, the Big Dipper appears at the 9 o'clock position, at the second innermost circle. The bright star at 10 o'clock is Arcturus; the Polar star is slightly below the heavenly North pole. In the austral (southern) sky, the two bright stars at 2 o'clock on the second innermost circle belong to Centaurus and point to the Southern Cross, slightly below and to the right; Sirius is the brightest star near the bottom center.