Map Projection and Scale Issues Flashcards
What is georeferencing?
− Georeferencing involves assigning a spatial location to an item of information.
− Process of taking map layer, assigning it a projection / coordinate system and coordinates, and translating/transforming it into position relative to some other spatial data
− Geocoding is putting points on map but georeferencing is making sure things (layers) line up
What are the three things georeferences should be?
Unique: they link information to exactly one location
Shared: they are understood by different users (Usually use longitude/latitude)
Persistent through time: they do not change through time
Why do we use longitude/latitude?
− The single-most comprehensive and powerful method of georeferencing
− Provides potential for very fine spatial resolution
− Allows distance to be computed between pairs of locations
− Supports other forms of spatial analysis
What are the 4 most common distortions?
− Shape
− Area
− Distance
− Direction
What is the name of the compromise projection?
Winkel Tripel
Why do you need the correct coordinate system?
So your layers will line up and you will have georeferenced correctly
What is Scaling?
Scaling is the process of reduction involved in moving from reality to map plane
How is scale expressed?
As a representative fraction
What is Ecological Fallacy?
An ecological fallacy occurs when it is inferred that the results used on aggregate zonal or grouped data can be applied to individuals who form zones or groups being studied” (Openshaw, 1984)
Ecological Fallacy: Inferences about the nature of individuals are deduced from analysis/observations on the group to which those individuals belong.
What is exception fallacy?
Inferences about the nature of groups are deduced from analysis/observations on individuals in those groups.
What is MAUP?
A challenge that occurs during the spatial analysis of aggregated data in which the results differ when the same analysis is applied to the same data, but using different aggregation units.
What are the two effects MAUP causes?
− Scale effect (Variation in results obtained when data for one set of areal units is replaced with another e.g. difference between Wards/Districts etc)
− Zone effect (Variation in results obtained from different ways of subdividing geographical space at the same scale e.g. the lines of the boundary can effect the pattern)
