Mapping

Maps

Maps can depict visible surface features (towns), underground features (subways), and abstract features (political boundaries)

Not possible to accurately represent round Earth on flat surface

Spatial concepts on maps—distance, direction, density, diffusion, linkage, flow, arrangement, accessibility

Latitude

Equator marks the zero degree parallel and is fixed by the laws of nature

Sailors measured latitude by length of day, height of sun, or known guide stars

Angle measured north or south from equator from 0° to 90°

Chicago--42° N

Longitude

Prime Meridian location is a political decision—Royal Observatory at Greenwich, England

Longitude measured by time—each hour’s time difference between ship and home port indicated 15 degrees

Intersect parallels at right angles Measured east or west 0° to 180° New York City--74° W

Minutes and Degrees

Basic latitude/longitude is degreeEach degree is divided into 60 minutesEach minute is divided into 60 secondsFor more precision on a location, specify

minutes or even secondsSometimes degrees are written as

decimals (36º 34.521 N)

Map Scale

Relationship between distance on the map and distance on the ground

Usually written as a fraction or ratio1:10,000 or 1/10,000 (1 inch of

measurement on the map equals 10,000 of same units on ground)

1 to 24,000 scale

1 to 100,000 scale

Map Scales (from USGS.com)

1 to 250,000 scale

Orientation

Never Eat Soggy WafflesNorth, East, South, West

Can use clock for directional reference “Dolphins at 1:00”

Good Map Elements (DOGSTAILS)

Date—when map was made Orientation—directions Grid—locates places on map Scale—map distance Title—what, where, when Author—who made map Index—map address of places Legend—what the symbols mean Sources—basis for map information

Map Types

Reference Political Physical Topographic Satellite

Thematic Choropleth Cartograms

Map Problems

When the National Geographic Society came out with it’s sixth Atlas edition, it contained approximately 10,000 changes, and was already out of date when it went for sale

Countries argue over namesKorea: East SeaJapan: Sea of Japan

Why Maps Lie

Cartographers are not licensed Maps distort reality Single map is one of large number of maps

that could be produced from same data Flat map stretches some distances and

shortens others Simplification Generalization

Common Map Errors

Based on incompatible sourcesMisspelled place-namesGraytone symbols changed by poor

printingCompiled from other mapsMap drafters having fun and including

fictitious townsInternational data based on inconsistent

definitions

Globe v. Map

Peel an orange into four equal pieces and lay the pieces side by side on a flat surface. Observe how the landmasses fit together.

Why we have different maps

Distortion exists with flat maps so cartographers use different projections to preserve selected properties (shape, size, distance, direction)

Map Projections

Mercator Projection

Good for navigation at sea because of straight lat/long lines

Renders Greenland as large as South America (yet 1/8 of size)

Flemish cartographer (1500s)

Map Projections

Robinson Projection

Accurate depiction of continent’s sizes and shapes

Distortion greatest at poles

Map Projection

J. Paul Goode (1923) Homolosine Equal-Area Projection Less distorted land masses by giving up continuous oceans

Map Projection

ConicBest for showing one section of Earth

without much distortion

Map Projection

PolarUsed mostly to show one hemisphere at

a timeAccurate for distance

and direction