Strand 2: Data Linkage and Thematic Mapping Flashcards
Example of Attribute data
Census Data
How much does the Census cost?
£482m - less than £1 per year
Characteristics of Census data
- Cross-sectional snapshot of population on single data
- Source of secondary data
- Can be examined at several geographical levels
- Total enumeration of national population
- Confidentiality is protected (Criminal offense to disclose individual data)
- Decennial since 1801
- Coverage = Comprehensive
- Coverage = Consistent (Asked same questions)
- Completion = Compulsory
Why do we need the Census?
- Useful source for students/ dissertation
- Provides Authorities with consistent nation/local information about: Population, Housing, Employment, Education etc…
- Businesses use it to assess markets and location planning
- Informs more than £50bn of local authority expenditure per annum
- Re-calibration of mid-year population estimates between censuses.
Name 2 online sources of Census Data
- CASWEB
2. InFuse (New system makes it easier for users)
Why is InFuse easier?
- Find census information which meets their needs
- Able to understand the meaning and origin of Census info
- Download Census information in forms that facilitate its use
What do all GIS resources need?
Metadata - important for the integrity of any analysis
What descriptive information does metadata provide?
- Content
- Quality
- Condition
- Origin
- Other characteristics e.g who, where, why
What is the primary objective of a Choropleth map?
To symbolise magnitude of statistics for areas
What data uses Choropleth maps?
Used for Standardised data e.g rates, densities, percentages (%)
E.g. Rate of various ethnicities in a city region
What is the convention for colors on a Choropleth map?
Bright Colors or Darker shading for high values
What maps are used for Count Data?
Proportional Symbol Maps - use symbols proportional in size to the values they represent
What are Dot Maps?
Where individuals or groups of events are marked with a dot, sees patterns such as clustering e.g John Snow
What are the 5 method of selecting class intervals?
- Equal range - e.g. 1-4, 5-9, 10-14 etc.
- Equal Count - ensuring the same number of counts in each class interval e.g. 5 data sets in each interval
- Natural Break - computer assigns classes based on natural clusters
- Standard Deviation
- Quartiles - e.g. class intervals created in quintiles, for example a new class interval after 20% people who are unemployed
What does choosing intervals make easy to do?
LIE or DISTORT truth
What are the disadvantages of mapping?
- Exaggerates the difference between two areas e.g. a place with a figure of 19.5% and a place with 20.5% are very similar results, but may look v different with 2 different colours
- Count data misleading as areas vary in both size and population
- Some geographical areas are v. big and some v. small - therefore v. big areas have a colour dominating a map giving misleading results
- The default class intervals i.e. Natural Break, can be misleading and incorrectly sorted
What are Proportional Symbol Maps?
Size proportional to the value they represent
Mapping COUNT data
E.g. Total number of motor vehicle deaths by county across the UK
