Choropleth mapping Flashcards
what does Choro + pleth mean
area + Value
what is a Choropleth mapping
mapping techniques which symbolize values applied to area
what are the aspatial requirements of choropleth mapping
derived data only
ratios, proportions, percentages, rates, commonly normalized.
what are 2 types of discrete areal units
Natural areal units
Artificial areal units
what is the MAUP
Data collected in arbitrary space results in simplification an error.
different aggregation of data creates different results
what are the effects of size of areal units in Choropleth mapping
- higher aggregation results in higher data loss
- impacts symbolization method
- perceived accuracy/ appearance
how does map scale affect Choropleth mapping
- ## smallest units must be visible
what is the difference between a choropleth and a chorochromatic map
chorochromatic maps are a form of choropleth but only show nominal area data
what are the two types of choropleth maps that show Interval, ordinal, or ratio data
- classless Choropleth map
- range graded choropleth map
what is one of the difficult aspects of range Graded Choropleth maps
choosing an effective classification interval
what are the six steps of choropleth mapping
- Judge suitability of data
- Order data (rank order)
- Classless or range-graded?
- Determine # of classes into which to divide data
- Determine class intervals (class breaks)
- Determine visual clues to differentiate between classes (Symbology)
what data is suitable for choropleth mapping
derved data,
- consider discrete/continuous
- aggregated by area
which is better, Range graded or classless choropleth maps?
depends, classless requires high computing power. Range graded is generally convention
what is the ideal number of classes
4-6
what does fewer classes convery
a louder message
what does many classes convery
shows more information, but messy
what are the 4 classification schemes we used
natural breaks
Quanitile
Equal interval
Standard deviation
How does natural breaks work
based on natural groupings in the dataset
how does quantile work
each class contains an equal number of features
how doe sEqual interval work
divides the range of attributes into equal sized subregions
how does standard deviation work
how much a feature varies from the mean
requires normally distributed data
when is class boundaries optimized
minimize variance within class, while maximizing variance between class
what does GVF test stand for
goodness Variance Fit test
what does GVF show?
it provides a summary statistic about the chosen classification method to show how good the scheme is.
what is a nested mean
mean of the data used to divide the data into two classes, values above and below the mean.
what is a skewness, Positive and negative
shows how the data is distributed, Positive skew is more 0, negative skew is greater values
what is a single hue progression
a symbolization method that only involves one colour, typically white - full saturation
what is a Bipolar Progression
using two colours to symbolize features, usually fully saturation one colour –> white –> full saturation another colour.
what is a Bivarite choropleth map
a map choropleth map that has two variables.
square table to show intensity
what is a good projection for Choropleth mapping
should use an equivalent projection
