Map Types and Projections

Opening Activity: What can maps show us? In table groups, list as many things as you can think of - be specific, and think of both physical and cultural items

ex: population density, per capita income Type 1: Choropleth Map -a thematic map which uses shaded or patterned areas to display a variable ex: population density, per capita income

Type 2: Dot Distribution Map -a map which uses a “dot” symbol to show the presence of a feature or phenomenon; shows spatial patterns ex: population distribution, location of natural disasters, farms, schools, etc.

Type 3: Proportional Symbol Map -a map which scales the size of simple symbols (circle, square) proportionally to the data found at that location ex: liters of coffee consumed per capita, population totals

Type 4: Isoline Map -a map with continuous lines joining points of the same value ex: elevation (contour lines), temperature, wind pressure

Contour Lines of a Face

Map Projections Transferring information from the spherical, or ball- shaped, surface of Earth onto a flat piece of paper is called projection. A globe, a spherical model of Earth, accurately represents the shapes and locations of the continents. But if a globe were cut in half and each half were flattened out into a map, the result would be wrinkled and torn. The size, shape, and relative location of land masses would change.  Source: National Geographic

Cartographer’s Dilemma Projection is a major challenge for cartographers. Every map has some sort of distortion. The larger the area covered by a map, the greater the distortion. Features such as size, shape, distance, or scale can be measured accurately on Earth, but once projected on a flat surface only some, not all, of these qualities can be accurately represented. For example, a map can retain either the correct sizes of landmasses or the correct shapes of very small areas, but not both.  Source: National Geographic

Videos Vox: https://www.youtube.com/watch?v=kIID5FDi2JQ National Geographic: Cartographer's Dilemma

4 Types of Distortion Shape- refers to geometric shapes of objects on the map Size (area)- relative amount of space taken on the map by landforms or objects on the map Distance- represented distance between objects on a map Direction- degree of accuracy representing cardinal directions (North, south, east and west) and intermediate directions (northwest, southwest, northeast, southeast) All four properties cannot be accurately represented, the cartographer (mapmaker) must decide which aspects are more important

What is the difference between these two projections in regards to shape, size, distance and direction?

Mercator

Mercator Useful: looking at equator, where distortion is minimized; nautical navigation Distortion= area (size) distortion; size is distorted especially at the poles, direction is true

Robinson

Robinson Use: for location, general reference Distortion= all four categories are slightly distorted

Winkel Tripel

Winkel Tripel Use: due to minimal distortion it is well suited for general purpose mapping, rarely used to map anything smaller than the whole planet Distortion= shape (especially at the poles), distance

Peters Projection

Peters Use: currently in limited use, but helps to promote better understanding of size and location Distortion= size is true, shape is distorted, location is true