data presentation- spatial data

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Geographical skills theory
Data presentation- spatial data
Maps
A map is the simplest form of displaying data over space when the relevant
features and data marked on. Maps need to have a scale; a title and north must be
indicated. The scale must suit the data, so a plan of a building would have a
different scale to a plan of an urban area.
Isopleths or isolines
This makes a spatial pattern out of point form data by using lines t join up the
points with the same value. The lines represent the same value at the points in an
area through which it passes.
The selection of intervals between isopleths is important if it is too big
then the isopleths may be placed inaccurately but if it is too small then the
map will be obscured by lines.
Consider the shape and size of the units for which data is available.
The location of plotting points. Are they central to the area or are they
located at the point the data was measured.
How was it decided where the line should go where there is no data?
Isopleths lines should be smooth not angular or erratic as we assume a
smooth transition between values but this may not be accurate in reality.
Choropleths
Density maps where areas are shaded to represent the average number per unit
area. Gives a quick visual impression of patterns. However:
Variations are hidden as it treats one area as a whole.
Scale of area divisions is important. There smaller the scale the more
accurate the choropleth maps.
Colours are difficult to use so they should be avoided as they rarely show a
smooth progression in density and colours often give unintentional meanings
such as blue representing water.
Located symbols
Proportional symbols can be placed on a map to show patterns. An effective
method is to use overlays to compare patterns as long as the symbols are on the
same scale.
Located symbol advantages disadvantages
Dot maps Simple to do Size of dots if they
Clear location of dots are small then they

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Geographical skills theory
Can use colours to can be hard to see but
show more than one too large and they will
pattern hide the map
Scale- confusing if
dots represent more
than one
Location of dot- hard
to tell of exact
location
Proportional Can deal with larger Size of circles: too
symbols numbers than dots small they can be hard
to see if they are too
large they can cover
the map
Scale: needs scale as
proportional to square
root of data value
Location…read more

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Geographical skills theory
Flow lines
Flow lines show the volume, frequency and make up of movements along routes. The
flow line is a variation of the bar chart but follows the route with the width
reflecting the size of flow. It's sometimes simplified to show direction and
distance but not the precise actual route.
Trip lines
Type of flow line that shows direction and volume but are straight line drawings
from origin to destination.…read more

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