Revision Flashcards
What is metadata?
Information which describes items in GIS
What does metadata provide?
Spatial extent of a dataset
Time when data were collated
Projection system used
File type
Examples of vector data
Digitising
GPS
Land surveys
Examples of raster data
Aerial photography
Scanning
Satellite Imagery
What is raster data and when is it used?
A grid of pixels or cells, and useful for continuous data
What is vector data and when is it used?
Representation of the world using points, lines and polygons, useful for storing data with discreet boundaries.
What are examples of topology?
Connectivity
Adjacency
Containment
Distance
What is an example of topology in use?
'’Which countries share a border with Russia?
‘‘Which cities are located within 25km of a river?’’
What are the five map projection types?
Conformal Equal Area Equidistant Compromise Direction
What does a conformal map do?
Preserves local angles and shapes
What does an equidistant map do?
Preserves distance from a reference point
What does a compromise map do?
Concentrates on making the map ‘look right’
What is the mercator projection?
Normal cylindrical projection
What is the transverse mercator projection?
Distances true along the central meridian
Used by the OS for their maps
What is the azithumal equidistant projection?
Distances are preserved, however distortion of area increases from the centre point.
