Flashcards in Map Styles Deck (17):

1

## What are reference maps?

###
Emphasis on spatial and attribute accuracy.

Nautical Charts, Topographic Maps, Aeronautical Charts

Slide 2

2

## What are thematic maps?

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Highlights patterns and distributions for spatial analysis

Choropleth, Dots, Graduated Symbol

Slide 3

3

## What are symbols for nominal and qualitative distinctions?

### Slide 5

4

## What are symbols for ordered quantitative distinctions?

### Slide 6

5

## What are choropleth maps?

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Very simple value (choros) by Area (plethos) Maps indicate the amount of something in a predefined place like a county, census tract, block group or country. The design of these maps is based on two factors:

1) Classification (creating categories)

2) Symbolization (creating symbols)

6

##
Research has shown that the maximum number of grey shades that can be distinguished accurately is about ___. Choropleth maps rely on the user to be able to ________-.

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5-7

state positively which group each area falls into

7

## For categories, Color use can extend the number of categories a little but, these are ranked data, so widely divergent colors are ________.

### Not a good strategy as they do not meet the expectations of the reader

8

## For choropleth maps, what are the three categorization cut points?

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Equal interval

Equal number

Natural breaks

9

## When do you use equal interval?

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If you want equal parts of the data range in each category

Each category is the same width, not good if outliers in the data (extremely low or high values)

10

## When do you use equal number?

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If you want equal representation of categories among map areas

An equal number of areas are in each category, does not consider the values only the order – ordinal

11

## When do you use natural breaks?

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If you want to be sure that the categories are most internally similar

Determine largest gaps in the data, also can be a problem if outliers exist

12

## What is the formula for equal intervals?

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(max - min)/ number = width

slide 13

13

## What is the formula for equal number?

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sort values low to high. Divide the number of values by the number of categories

number of values/ number of categories = number

Slide 15

14

## How do you compute natural breaks?

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Sort Data low to high

Compute the “breaks”

Place category breaks at the “n-1” largest breaks:

Slide 17

15

## When making do maps, what are the two decisions you need to make?

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Classification: The number of items per dot – we are mapping counts of objects such as people, so we have too many to show each individual. The classification concept is very simple:

Take the count of people/cows/etc. and divide by the dot value to get the number of dots.Look over the number of dots to see if they are: Enough in small counts. Few enough in large counts. The outcome is not always so simple.

Symbolization: the dot size is variable for visibility, but dots usually exaggerate actual size of the objects they map.

16

## Instead of placing a dot for every item, what can you do?

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Make a symbol larger in the proportion to the number

Base size: what is the smallest symbol size to be?

Base Value – how many items will that size represent

17