GUS: 0262Fundamentals of GIS

Lecture Presentation 2:

Cartography in a Nutshell

Jeremy Mennis

Department of Geography and Urban Studies

Temple University

Maps as Models

Maps are models of reality.

They emphasize some aspects of reality in a cartographic representation while ignoring or greatly simplifying other aspects of reality.

Scale

the amount of reduction in the representation of a real world geographic phenomenon on a map.

or, the ratio of map distance to earth distance

1:24,000

1 inch = 2000 ft

1 2000 ft

verbal scale

representative fraction

bar scale

Geometric Representation

Points

Lines

Polygons

Generalization

Generalization

Measurement Levels

Nominal: equivalence

eg. land cover (residential, industrial)

Ordinal: ranking

e.g. city size (small, large)

Interval: ratio assuming an arbitrary 0 value

e.g. temperature in degrees F

Ratio: ratio assuming a true 0 value

e.g. temperature in degrees K

Map Projections

a means to depict the spherical earth on a two dimensional medium

cannot simultaneously preserve all of these properties of the earth in two dimensions:

shape (of a region)

distance (between two points)

direction (bearing from one point to another)

area (of a region)

Map Projections

Map Projections

Conformal projection

preserves direction

e.g. Mercator

Equal area projection

preserves area

e.g. Alber’s equal area

Geoid and Datum

Geoid: a model of the earth’s shape

Clarke 1866

GRS80

Datum: reference point for establishing horizontal control

NAD27 uses Clarke 1866

NAD83 uses GRS80

Coordinate Systems

provide a spatial referencing system to locate points on the earth surface

spherical coordinate system

coordinates that describe locations on a sphere

planar coordinate system

coordinates that describe locations within a two dimensional Cartesian space

Spherical Coordinate Systems

latitude and longitude

parallel: lines parallel to equator

meridian: lines going from pole to pole

Planar Coordinate Systems

rectangular grid with X and Y axes

X: easting

Y: northing

point is defined by X,Y coordinate

Planar Coordinate Systems

Universal Transverse Mercator (UTM)

units in meters

transverse cylindrical projection

60 vertical zones cover globe

northing in meters from equator

easting in meters from false origin 500,000 meters west of zone central meridian

Planar Coordinate Systems

Universal Transverse Mercator (UTM)

Planar Coordinate Systems

United States State Plane Coordinate System

units in feet

projection in transverse Mercator or Lambert’s conformal conic

tied to U.S. datum

one or more zones for each state with a false origin southwest of the zone

Planar Coordinate Systems

United States State Plane Coordinate System

Types of Maps

Reference Map

Thematic Map

Qualitative

Quantitative

Dot Map

Isarithmic Map

Cartogram

Proportional Symbol

Choropleth Map

Dot Mapping

Isarithmic Mapping

Cartogram

Choropleth Mapping

Choropleth Mapping

Choropleth Mapping

Breast Cancer Incidence by County in North Carolina

Classification in Choropleth Mapping

Constant Intervals Equal Interval

Standard Deviation

Variable Intervals Quantile

Arithmetic Progression

Geometric Progression

Natural Breaks Visual

Maximum change in slope

Optimal (Jenks)

Classification in Choropleth Mapping

Thematic Map Elements

Title

Legend

Scale

Credits

Mapped and unmapped areas

Borders and neatline

Map symbols

Place names and labeling

Thematic Map Elements

For more on choropleth mapping:

http://www.personal.psu.edu/faculty/c/a/cab38/GEOG321/05_choro02/choro1_02.html