Cartographers affect how we perceive our world

Representing the earthA geographical map is a two-dimensional, geometrically accurate representation of a three-dimensional space. Inevitably, however, distortion is introduced when a globe is made to lay flat.

This teacher uses a physical map of Europe to explain his point.

Ancient map

Claudius Ptolemy (150 AD) map drawn from Ptolemy's coordinates for a 1482 edition of his Geographia

Types of map projections

• Mercator• Mollweide• Robinson• Peters• Polar

Each introduces some error inherent when three-dimensional sphere is flattened into two dimensions.

The earth is round. The challenge of any world map is to represent a round earth on a flat surface.

Which projection?

Map Projections

Cylindrical Projection: is based on a cylinder tangent to the equator. Good for equatorial regions but greatly distorted at high latitudes.

Though the Mercator projection is particularly good for navigation, it becomes increasingly distorted toward the poles, resulting in areas appearing much larger than they actually are.

Mercator projection

The distortion caused by a Mercator projection makes Greenland appear larger than Australia when, in fact, it’s one-third its size.

The Eckert projection tries to keep the countries in relative proportion but still flattens out near the poles.

The Peters projection is an area-accurate map

The Robinson projection

The Robinson projection is based on tables of coordinates. The projection distorts shape, area, scale, and distance in an attempt to balance the errors of projection properties.

PolarThis projection is used by pilots to determine the shortest route between two points on the globe.

Upside down? Depends on our pre-conceptions

Differences between map projections

Map Symbols

Legend

Compass RoseThese keys should be included on any map to which they apply

Strait

Isthmus

Scale

Landsat

A series of satellites that can photograph the entire earth in 16 days.

Global Positioning Systems (GPS)

This system uses a series of 24 satellites called the Navstars to beam information to earth about an object and its location of the earth’s surface.

“Like a huge piece of orange peel that refuses to be flattened without tearing at the edges, the globe cannot be forced into two dimensions without distortion. But that distortion can now be minimised “

Atlas technology

Geographic Information Systems (GIS)

A system that uses digital map information to create a databank to produce specialized maps.

Links• http://csiss.ncgia.ucsb.edu/cookbook/ima

ges/Map%20projections.jpg• http://www.empereur.com/ptolemy.html

Links