GIS Lecture: Maps

Summary Thematic Maps (Choropleth) Use of Color Categorical Maps Graphical Hierarchy

Thematic vs. Categorical Thematic maps – Quantity - different amounts Categorical maps – Quality - different types

Thematic Maps

Classification Intervals Edit the classifications and layer properties

Original Map (Natural Breaks) Uninsured U.S. Population, 2005

Custom Map (Equal Intervals) Uninsured U.S. Population, 2005

Other Numeric Intervals Pittsburgh, PA: Neighborhood proportion under poverty and average BMI per neighborhood BMI ! 18.5 - 24.9 25.0 - 29.9 30.0+ Percentage in Poverty 0 - 12.5% 12.51% - 19.99% 20.0% - 39.99% 40.0% - 70.10% Data Sources: BRFSS data, 2000;City of Pgh City Planning Dept., U.S. Census 2000

Use of Color

Color Overview Colors have meaning Cool colors calming, Warm colors exciting Cool colors appear smaller than warm colors and they visually recede on the page, so red can visually overpower and stand out over blue even if used in equal amounts Colors have political and cultural meanings

Color Overview Hue is the basic color Value is the amount of white or black in the color Saturation refers to a color scale that ranges from a pure hue to gray or black

Color Overview Monochromatic color scale is a series of colors of the same hue with color value varied from low to high

Customized ramps Customize the Properties of a layer

Color Wheel Guidelines Use opposite colors - those directly across from one another to differentiate graphic features 3 or 4 colors equally spaced - good for differentiating graphic features Use adjacent colors for harmony - such as blue, blue green, and green or red, red-orange, and orange

Contrasting and Non-contrasting Colors

Dichromatic Color Scale Two monochromatic scales joined together with a low color in the center, color increasing toward both ends Natural middle-point, such as 0 for some quantities (profits and losses, increases and decreases)

Change Map Example

Color Spots White background allows color spot to be visualized

Color Spot Ramp

Categorical Maps

Categorical Map Example - Light Pole Owner

Categorical Map Example - Zoning

Categorical Map Example - Street sweeping days

Graphic Hierarchy

Graphic Hierarchy Assign bright colors to the most important graphic elements Such graphic elements are called “figure”

Graphic Hierarchy Assign drab colors to the graphic elements that provide orientation or context, especially shades of gray Such graphic elements are called “ground”

Graphic Hierarchy Place a strong boundary, such as a heavy black line, around polygons that are important to increase figure Use a coarse, heavy cross-hatch or pattern to make some polygons important, placing them in figure

Graphic Hierarchy

Summary Thematic Maps (Choropleth) Use of Color Categorical Maps Graphical Hierarchy