Strand 2: Migration Measures and Geospatial Visualization Flashcards
What are the 5 measures of Migration (or flows)?
- Gross Migration Flows
- Net Migration (IN-OUT)
- Net Migration Rates
- Migration Churn
- Migration Efficiency
What is Migration Efficiency?
- Tells us how efficient net migration is in redistributing the population in a system
- Defined in different ways depending on the flows involved
What can be expressed as a Zone-Specific ratio?
Migration Efficiency - Net migration as a % of total out-migration plus total in migration
What can be expressed as an Origin-Destination Specific ratio?
Migration Efficiency
What can be expressed as a system wide index (a.ka. Migration Effectiveness Index)
Migration Efficiency
What is Geovisualisation?
- Geographical/ geospatial visualisation
- Allows for data exploration and decision making
- Communicates geospatial information
- Use of computer technology/ graphics to explore data in a visual form and acquire a deeper understanding
Talk about the developments and changes in Geotechnology
Significant Developments in the last 30 years:
- The computing technology for storing and processing spatial data
- The software available for visualization and analysis
- Games industry pioneers of creation of virtual reality e.g 3D Building in Google Earth
E.g. Landmap - Building heights - Data base providing accurate height data for every building across London, can use with range of GIS programs that enable height-citrical applications to be undertaken for the built environment.
What are the problems of visualising data on a conventional map?
- Too many polygons
- Size of polygons are too small
- Zooming in only maps certain areas
What is a Cartogram?
- Map projections that reduce distortion
- Used when distortions in shape, distance or shape are made explicit and seen as desirable
- Typically drawn so that sizes is in proportion to some attribute
What is an isodemographic map?
- A diagrammatic method of displaying countries, administrative area or zones within a country in 2D maps with each area acetyl proportional to the population density of the area
- Provides a frame for the analysis and communication of social and economic variables
7 reasons why we produce Cartograms?
- To show variation over space
- Alternative base map used in research
- Easy bi-variate mapping
- Ability to shock and impact
- To show distributions that are more concealed by conventional mapping
- A more socially just form of mapping because they give people more equitable representation (variable mapping has greater importance than land area)
- Allows for a better understanding of the spatial structure of society (Dorling, 1994)
What are the 5 methods of creating Cartograms?
- Physical Accretion Models
- Mechanical methods
- Competing Cartogram Algorithms
- Circular Cartograms
- Cellur Automata Cartograms
What is a circular Cartogram?
- Each region is drawn as a circle with its area proportional to its population
- Useful for population data from Censuses
- Circles are moved about by repulsion and attraction forces
- Go to 100’s of iterations to avoid overlapping
- Each region is treated s an object in a gravity model which is repelled by other overlapping circles but is attracted to circles, which were neighboring regions on the original map
What are the various Software to create Cartograms?
- GeoDA
- ArcGIS
- MapViewer
- Mapresso
- ScapeToad
- Cartogrammer
What is the difference between Flow Mapping and automated Flow Mapping?
Flow mapping: manual mapping of flows crossing borders
Automated: Use of line of differing widths to depict movement of goods or people. (Waldo Tobler)
(MapInfo - Spider Graph or Distance Calculator tool)
