1. Using Presentational techniques in Geography

2. What are techniques of presentation?
Generally these come from the list of cartographic( map) and graphical skills on the specification

3. Cartographic techniques include…
ATLAS MAPS
ORDNANCE SURVEY MAPS
SKETCH MAPS
FLOW LINES
DESIRE LINES
TRIP LINES
CHOROPLETH MAPS
ISOLINE MAPS
DOT MAPS…

4. Graphical techniques include..
LINE GRAPHS
BAR CHARTS
SCATTERGRAPHS
PIE CHARTS AND PROPORTIONALCIRCLES
TRIANGULAR GRAPHS
RADIAL DIAGRAMS
LOGARITHMIC GRAPHS
DISPERSION DIAGRAMS
KITE DIAGRAMS..

5. CARTOGRAPHICAL MAPS Dot maps: Advantages and disadvantages?

6. What are dot maps and why are they used?
Dot maps are useful ways of showing the density of a particular variable such as population. They can also indicate the distribution of a particular variable.
Unlike a choropleth map, it is possible to estimate the numbers in a particular place, provided that each dot is clearly visible.

7. Dot maps- strengths and weaknesses
Good
Spatial -show density and distribution
Accurate- can use a scale e.g. one dot represents 10 students
Easy to plot
Bad
Clustering may make it impossible to plot and interpret e.g. in urban areas as the dots may begin to ‘merge’
Exact numbers on the map= impossible to calculate
Can be misleading when there is a large difference in densities between places. Scale can be a problem e.g if each dot = 100,000 people, areas that are more sparse than this would not receive a dot, implying that nobody lived there at all…not necessarily true.

8. What’s the difference? Linear scale( arithmetic) graphs are useful
when you want to show absolute changes
in the data. The scale chosen should always
allow the FULL RANGE OF DATA TO BE PLOTTED FOR EACH
VARIABLE.
A logarithmic graph is drawn as an arithmetic line graph
Except that the SCALES ARE DIVIDED INTO A NUMBER OF
CYCLES, EACH REPRESENTING A X 10 INCREASE IN THE
RANGE OF VALUES. Logarithmic graphs are good for
showing rates of change ( the steeper the line, the faster
the rate) and they also ALLOW A WIDER RANGE OF DATA
TO BE DISPLAYED.

9. What are logarithmic scales are why are they used?
Logarithmic scales are a specialised variation of a line graph.
The difference is that the scale is not even( as it is with an arithmetic/ linear scale)
Where an arithmetic scale generally shows increases at equal intervals, a logarithmic scale does not.
Instead, it uses a series of cycles( usually 3 or 4) where increases occur in multiples of 10.

10. What is a logarithmic scale. Why do geographers use this
What is a logarithmic scale? Why do geographers use this? Advantages and Disadvantages?

11. So what’s the difference between semi- log and log-log graphs?

12. What is the difference between log- log and semi- log scales?
Log- log graphs use the logarithmic scale on both the x and y axis.
Semi- log graphs only use the logarithmic scale on the y axis. Instead, the x axis is an arithmetic scale.(This is particularly useful if you are interested in displaying data with a large range of values and if you are interested in change over time)

13. Strengths and weaknesses of logarithmic scales
Good:
For data with a very large range of values
Useful for showing rate of change- a steeper line suggests a faster rate of change
Bad:
Easy to make errors plotting
Zero cannot be plotted
Negative and positive values cannot be displayed on the same graph.

14. Let’s revise the Hjulstrom curve

15. Bar charts/graphs
Look at the bar chart below..Hum…!!

16. Is this bar graph good or bad?

17. Bar graphs: pros and cons
Good
show relationships between 2 or more variables
show proportions
visually attractive
bars used combinations of qualitative and quantitative variables
Can show positive and negative values
Simple to construct and read
Bad
Plotting too many bars makes it appear cluttered- less easy to interpret
If wide range of data impact lost as it is difficult to read accurately
Become more complicated if uneven class intervals
Using too many or too few classes can mask important patterns in the data

18. What does this graph show? What type of graph is this?
A scattergraph

19. What is a scattergraph used for? (see pink booklet p.28)
A scattergraph is a type of graph in which plotted points often appear as dots scattered across the graph paper.
It is the simplest and most visual way in which to show correlation.
You would use this technique when investigating relationships between two variables.

20. Scattergraphs:pros
1.Useful when considering two variables such as discharge of a river and distance downstream
2.Used when data is available for many locations (e.g individual river sites could be compared)
3.Shows anomalies
4.Trends indicated by best fit line
5.Correlations easily seen by direction of best fit line
E.g. Blencathra river study ( see cream booklet for how to construct and usefulness of technique)

21. Scattergraphs - cons
Does not show statistical strength of relationships
Only two variables presented at any one time- can be seen to be limiting

22. Pie charts

23. Pros and cons of pie charts:
Bad:
Less than 3 segments look simplistic
If many segments a similar size; it is hard to interpret
Good:
visually attractive
shows proportion of components clearly using % totals
shows scale

24. Proportional circles

25. Using Proportional Symbols
Proportional circles are just one way that geographical features may be represented on a map. Other symbols may also be used , e.g squares, triangles and so on ( see map) . In each case it is essential that the SIZE of the SYMBOL is PROPORTIONAL to the VALUE IT REPRESENTS

26. Proportional circles Good visually attractive location shown
provide context
show scale
show proportions
Allows comparisons between data sets
Bad
Very hard to calculate
Size may obscure location or mean less accurate positioning on maps, i.e. in cities

27. Consider this example: to display the composition clay , silt and sand in a soil sample:

28. Triangular Graphs Why useful?
Triangular graphs are useful in showing the clustering between three different variables
( e.g. the different percentages of clay, silt and sand in a soil sample)
They only work where the variables are given in percentage( %) form

29. Radial diagram- what does this show?

30. What is a radial diagram?
Radial diagrams are used to plot data in a circular fashion around a central point, usually
( but not always!) reflecting compass bearings.
Radial diagrams come in many different forms and examples include
i) a wind rose diagram( which can be used to plot wind direction)
ii) a polar graph, which can be used to display changing activity over different time periods( e.g. pedestrian flows over a 24 hr period)

31. Radial Diagram showing strength and direction of wind speed

32. Radial diagrams Good: Visual impact- easy to see patterns
Spatial- directional
Useful to show changes over time
Bad:
Hard to plot

33. Radial Diagram From what direction is the prevailing
( most common) wind in Washington state shown on the diagram?
South
Roughly what percentage of wind is westerly?
3.5%

34. DISPERSION DIAGRAM

35. What are Dispersion Diagrams and why are they useful?
Dispersion diagrams allow you to investigate the spread of a set of data
By plotting all of the data set on a vertical axis, the range within the data set becomes visually apparent.
It is also possible to identify any clustering within the data set
The data set has usually been plotted around the median value
It is also possible to calculate the mean, mode,lower, upper and interquartile ranges and standard deviation for the data set

36. The ‘dispersion of data’ means the spread of data around the mean(average)
What are mean, mode and median?
What is the range?
What does interquartile range mean?…….

37. Advantages of Dispersion Diagrams
1. Shows clearly the spread of data from the mean
2. Clear visual representation of the data
3. Gives a clear indication of the reliability of the data
4. Makes it possible to calculate the mean, median, mode, lower quartile, upper quartile, interquartile range and standard deviation
5. Can compare graphs easily
6. Anomalies can easily be identified

38. Disadvantages of Dispersion Diagrams
1. Only really works with a large data set
2. They are only really useful to display ONE DATA SET at a time
3. If you want to compare many different data sets it is quite a time consuming technique

39. Cartographic techniques include…
ATLAS MAPS
ORDNANCE SURVEY MAPS
SKETCH MAPS
FLOW LINES
DESIRE LINES
TRIP LINES
CHOROPLETH MAPS
ISOLINE MAPS
DOT MAPS…

40. Flow line map

41. Why is the thickness of the arrows important
Why is the thickness of the arrows important? What is the route of travel?

42. Why are flow lines used on maps?
1.A flow line is used on a map to show the actual flow and direction of something ( e.g. traffic)
2.The flow line is drawn proportional to the number travelling along the actual route by the use of a suitable scale.
3.Flow lines are more likely to be used on large scale maps ( see previous maps)

43. Strengths and weaknesses of Flow line maps:
Good
Straight forward visual impression
Can see sequences- e.g. how tributaries feed main rivers
Scale / width of lines shows proportions
TASK: TRY Q 6ai)
Bad
In order to achieve a clear image
Real distance is distorted
Direction is distorted

44. Desire lines on maps

45. Why are desire lines used on maps?
1. Desire lines are lines on maps which are drawn directly from the point of origin and which take no account of a specific route or direction.
2. They are similar to flow lines, however, in that the width of the line is proportional to the quantity of movement .
3. You may have used them for CA at GCSE?!
4. Desire lines are usually drawn on smaller scale maps showing movement between regions or even different parts of the world.

46. Strengths and weaknesses of desire line maps
Good
Easy to construct
Easy to interpret
Good to show spatial awareness on map- straight lines represent the movement of goods or people from a regions to a central point
Bad
Maps can become easily crowded and complex if large amounts of data are to be plotted( N.B The problem can be overcome by drawing a closed circle around the destination point and then excluding all desire lines that fall within this circle)
Does not show actual route
TASK: TRY Q 2

47. Trip lines to show journey directions home after work:

48. Trip lines
Trip lines are a variation on the desire lines concept. They are used to display information related to the trips or journeys taken by individual people, say home from work.
On a map, trip lines look like spokes on a wheel.

49. Strengths and weaknesses of trip lines
Good
Easy to visualise and interpret
All trip lines come from one central point so variation from this point can easily be identified
E.g. it is possible to see the sphere of influence of Much Wenlock ( see previous map)
Bad
No way of displaying density as lines are all the same width
Does not take individual routes into account

50. Isoline maps

51. What are isolines on maps?
Isolines are lines that represent the same value along their whole length.( ‘iso’ means ‘the same’)
You will have come across them before in geography e.g.
Contour lines
Weather maps( isobars)
In CA work when presenting pedestrian flows
River depth data( isovels)

52. Isovels to show changing velocity measurements along a straight river cross section

53. Isovels to show changing velocity measurements along an asymmetric meander cross section

54. Isolines on maps: Strengths and weaknesses
Good
Spatial
Represent equal values along their length.
Can keep point information as well for accuracy on map
Can add colour- density shading to enhance patterns/ trends
Bad
Allow flexible interpretation of data
There may be errors in the plotting
TASK: June 2011
Q 1bi) and bii)
N.B SEE EXAMINERS REPORT FOR ERRORS!!!!!!!!!!!!

55. 2. Choropleth Maps

56. What is a choropleth map?
Choropleth mapping is one of the most widely used techniques in displaying geographical data( e.g population densities, rates of disease etc..)
The technique works by using a system of colour, grey scale or line density to show how the density of your data changes from place to place…

57. Choropleth Maps
Good
visually effective – reader can see general patterns
location shown
provide context
show scale
show densities
Easy to construct
Bad
Map assumes the whole area has the same value, but there could be important variations
Abrupt changes in boundaries- realistically would merge, therefore are not accurate