Lecture 3

Question 1

Data types

Nominal

Answer 1

• Establishes identity
• Not used for mathematical calculation
• E.g. postcodes, soil type/ other land cover types

Question 2

Data types

Ordinal

Answer 2

• Establishes a comparative order or ranking, still don’t have a numeric to give an exact quantity but gives an indication of what is ‘better’ or ‘worse’
• A is greater/better than B
• No accurate relative information
• How much greater is A than B?
• E.g. Best counties to live in

Question 3

Data types

Interval

Answer 3

–Allows calculation of differences
•A is 10 points greater than B
–No origin value
•Cannot say A is twice as great as B – not relative to an origin value
–E.g. Temperature

Question 4

Data types

Ratio

Answer 4

–Have absolute or real zero, example is age (everyone starts from same point_
–Differences are significant and calculations predictable, put them into models, Jane is twice as tall as Sam etc.
–E.g. age, distance

Question 5

Raster Data (Pixel) Types in 
ArcGIS

Integer – Whole Numbers

Answer 5

–Best used to represent discrete data (thematic or categorical).
–E.g. land cover

Question 6

Raster Data (Pixel) Types in 
ArcGIS

Floating Point

Answer 6

–Best to represent continuous data (surface data)

–E.g. elevation, air pollution- can have a range of values

Question 7

Raster Data (Pixel) Types in 
ArcGIS

For both data types:

• Integer – Whole Numbers
• Floating Point

Answer 7

–Unsigned means all numbers are positive
–Signed can be negative
–No Data values – the absence of a value (not a value of zero!)

Question 8

Symbology

Answer 8

atch with real world for comprehension
By symbol e.g plane for airport
By colour e.g blue for river
Point data can use arbitrary symbols or icons
Ordinal data should have logical progression
Bigger road- thicker line

Question 9

Different types of symbology:

Answer 9

Based on data type
Map purpose
Clarity

Question 10

Raster symbology

Answer 10

Interval and radio data
Colours / shading show sensible progression
High to low
Reinforced with legend

Question 11

Map types and data classifications

Two main map types

Answer 11

•Topographic
–Reference maps containing a diverse set of information
–Can be a composite of different information
Some information can be left out, information useful for purpose will be left in…

•Thematic
–Relates to a particular theme or topic
–E.g. population, crime, income, land use

Question 12

Proportional symbol

Answer 12

E.g Earthquake intensity
Quantitative point data
Choice symbol size range- you can pick the range size

Question 13

Dot density

Answer 13

•Used to show spatial distribution
•Dot usually indicates a count of the variable
More dots in an area the higher the average income
Different colours can represent ethnicity, also.
–Aggregate location
•Can map different categories

Question 14

Choropleth

Answer 14

•Main type of map for quantitative area data
–Choice of intervals (number and size)
–Choice of shading
–Choice of spatial unit

Question 15

Equal-Interval

Answer 15

•Data divided into a chosen number of equal intervals or classes
•Simple for dividing up the data
Clear distinction in bands
•Can give unequal distributions
•Can give empty classes

Question 16

Quantile

Answer 16

• Data divided so an equal number of values fall in each class
• Quartile = 4 classes (Quintile = 5 classes)
• Can give irregular intervals
• No indication of frequency distribution of data

Question 17

Natural Breaks (Jenks)

Answer 17

• Divides into classes according to natural breaks between groupings of data
• ‘Common sense’ method
• Reliant on data providing clear natural breaks

Question 18

Standard Deviation

Answer 18

• Divides data according to distance from the mean (standard deviation)
• Intervals determined from the data
• Can give unusual class boundaries

Question 19

Why are paper maps still useful?

But…

Answer 19

–Transportable
–Reliable
–Easy to use

•But…
–Fixed scale/extent
–Static view
–Flat

Question 20

Why is GIS good?

Answer 20

•GIS more flexible
–‘seamless’
–Can be dynamic (animated)
–3-D visualisation
–Interactive (layers added/removed)

Question 21

Map design

Answer 21

•Purpose or agenda
–What will be mapped
–Target audience
•Representing reality
–Projection- means of getting 3D data sets onto a map
–Spatial referencing
–Features and data types
–Scale
–Generalisation
–Symbology
–Annotation

Question 22

Scale

Large scale

Answer 22

Covers small areas
Large amount of detail
1:1000
1:25,000

Question 23

Scale

Small scale

Answer 23

•Covers large areas
•Small amount of detail
–1:250,000
–1:1,000,000

Question 24

Ratio

Answer 24

Units do not matter as long as they are the same.

Question 25

Map composition

Answer 25

• Map body
• Inset/Overview map
• Title
• Legend
• Scale
• Direction (North Arrow)
• Map metadata (projection info, date, author)
• Copyright
• Reference grid

Question 26

Map Presentation

Answer 26

•Clear, descriptive title with key information:
–Location
–Content
–Date
•Map body should be largest element on the map – Zoom map content to fit.
•If using a map template, do not leave unused placeholders, e.g. ‘Click to enter map title’!
•Think about who will see it and how they will use the map.

Question 27

Legend

Answer 27

• All items in the legend should be visible on the map
• Plain English layer names in legend – not filenames or field names
• Number of decimal places on legend labels

Question 28

What is best used to represent discrete data (thematic or categorical)?
–E.g. land cover

Answer 28

Integer – Whole Numbers

Question 29

What is best used to represent continuous data (surface data)
–E.g. elevation, air pollution- can have a range of values

Answer 29

Floating Point