GEOL 452/552 -

GIS for Geoscientists I

Lecture 5

1

Overview• HW 1 graded, solutions on WebCT (slides & solutions)

• HW 1 - ex 4 - Lake area unit

• More of Chapter 2: Types of data used in maps

• Skip most of Raster display for now (come back in

Chapter 8)

• Raster_display.pdf - How to display raster data

(supplemental material from textbook on WebCT)

• Lab: Tutorial ch 2, 33-> to 45-> and 62 -> to 64 ->

• No new homework (*) until next lecture (Thursday)

2

HW 1, ex4: What unit is the Lake’s area in ?

3

Choroplethmap,

ArcMap:graduated

color

4

Data type vs. ArcGIS symbolization

Nominal data

Categorical data

Ordinal data

Ratio/Interval data

Single symbol map(labels if needed)

Unique values map

Graduated color (polygons)

Graduated symbol (points, lines)

Dot Density

Chart maps

If numericIf n

on-numeric

5

Nominal Data

• Describes names of feature

• Nominal data = names (words, computerspeak: “strings”)

• name of state, land owner, etc.

• “Name”: codes or indices (e.g. FIPS for counties, soil-codes, zip-codes)

• Single value: same symbol / appearance

• Only attribute “visualization” via labels

6

Categorical Data• Places features into distinct

categories based on an attribute/field (here: Road types)

• Different values (names, types) within each category (“Freeway”)

• Examples: Landuse, types of crop or animals, geologic units

• ArcGIS: Symbolize as Unique values (limited number of types of objects)

Geologic units

7

Making a unique values map

State subregions

Note: several features can share a color

8

Numerical Data

• Deals with numbers (Zip code? No!)

• Type A: Ordinal = rank (1., 2., 3., etc.)

• Examples: Rankings of: state by population,

universities, grades, taste

• Type B: Decimal numbers (5.1, 2.3) or integers (5, 1, 8)

• Examples: Length, Temperature, $, population, rainfall

• Interval vs ratio type: ratio needs a meaningful “0

point “(Celsius system vs. Fahrenheit or pH)

9

Mapping numerical data• Interval and ratio data: need to make classes before

mapping (need find class boundary, more next lecture)

• Show as variations in symbol size, thickness, or color (lightness, hue) or combinations

What are the class boundaries here?

10

Graduated color maps

County population in 2000

more on Classification next lecture

11

Types of maps symbolized as Quantities

12

Chart maps• Symbol (pie, bar) showing several

attributes at once

• Good for showing distributions and proportions

• Pie chart:

• color + slice size for race distribution (3 attributes)

• Pie size for absolute number of people

• Shape (states) used only for locations

Two attributes:

Eaten, not-eaten

13

Bar Charts (histogram)Select 1 attribute for each bar

here: “ordered” color scheme

14

Multiple attribute maps

State subregion AND population

15

Lab

• Raster_display.pdf - How to display raster data

(supplemental material from textbook on WebCT)

• Next lecture (still ch. 2): classification of numeric data

• Lab: Tutorial ch 2, 33-> to 45-> and 62 -> to 64 ->

• Officially: no new home work today, next HW (HW 3) on

Thursday (due Sep. 16)

• In-officially: HW3 will be: ch. 2, ex. 10, 8, 9

• After tutorial you can already do ch 2., ex 10

16