1. Maps and mapping
Spatial models of the real World:
Traditional paper maps

2. Why do we need models?
The real World is too complex to
manage in its entirety. Models
give us a simple manageable
representation
A map gives us a simple
model for studying what we
are interested in

3. Maps: what they are, what they show
• Map: a representation, by graphical means,
of selected features of the Earth
– A map is a scale drawing of only a selection of
features

4. Maps: what they are, what they show
• Map: a representation, by graphical means,
of selected features of the Earth
– A map is a scale drawing of only a selection of
features
• A map is a model: all models are wrong

5. Maps: what they are, what they show
• Map: a representation, by graphical means,
of selected features of the Earth
– A map is a scale drawing of only a selection of
features
• A map is a model: all models are wrong
• If you use an existing map, it may be the
wrong selection of the wrong features at the
wrong scale for your purposes
– If you cannot find a suitable existing map, you will
have to create your own

6. Coates Farm, map of selected features:
simplified detail, shown by line and text symbols

7. Coates Farm, 1:50,000 Ordnance Survey map:
different detail, shown by point, line, area and text symbols

8. Map symbols
colour and texture also used
Manor Farm
Point: towns, buildings, sample points
Line: roads, streams, boundaries, contours
Area (polygon): fields, soils, lakes
Text: names, heights, explanations

9. Map symbols example:
D.R. of the Congo (formerly Zaire)
Town locations:
points
Key to symbols
given in the
“legend”
Lakes & countries:
polygons
Roads and borders:
lines
Colours used to
differentiate
features
Range of text
styles to show
hierarchies.

10. Problems with mapping
The Earth is a spheroid and maps are flat
– map projections
The Earth is huge and maps are tiny
– scale reduction
How do you tell someone which piece of the
Earth your map shows?
– Agreed co-ordinate systems

11. Map projections:
flattening out the curved Earth

12. Map projections:
flattening out the curved Earth

13. Map projections:
flattening out the curved Earth

14. Three mathematical projection examples

15. Three mathematical projection examples

16. Three mathematical projection examples

17. Three different projections
same place

18. An interrupted projection:
distortions concentrated into “unimportant areas”

19. Problems with projections
They always distort one or more of:
– distance
– area
– shape
– direction (angle)
Type of projection chosen dependent on which
of these is most important for the intended
use of the map

20. Scale reduction
Drawing a big World on small paper
Mathematical reduction. 1:1000
– 1 unit on map = 1000 of the same unit on the
ground

21. Scale reduction
Drawing a big World on small paper
Mathematical reduction. 1:1000
– 1 unit on map = 1000 of the same unit on the
ground
Limit to scale reduction set by the thickness of
line that can be drawn
– The red line of an A road on a road atlas is about
300m wide, to “scale”

22. Same place, different map scale

23. Defining position: co-ordinate systems
How do you say where something is?
– Description: “five miles beyond the hump back
bridge, on the right”
– geographical co-ordinates: Latitude 23o North
Longitude 12o East
– grid reference: 12767m E 1356m N

24. Geographical co-ordinates
Latitude and longitude

25. Grid co-ordinates;
applied to a projected map
Base map projected
using a “Universal
transverse mercator”
(UTM) projection.
Grid laid over map.

26. Creating your own map
Basic principles of map creation:
– Forecast the end users’ needs
– Select the features to be shown
– Simplify the features
– Symbolise the features

27. Forecast
• Decide who is going to use your map and
what they will use it for
• Define the geographic extent of their area of
interest
• Find out the level of map use experience of
the end user
• Then start planning your map

28. Compile mapping data and select what you need
Existing
maps

29. Compile mapping data and select what you need
Existing
maps
Aerial photos

30. Compile mapping data and select what you need
Existing
maps
Aerial photos
Farm records

31. The new land use map:
data selected, simplified and symbolised
Mapunit.shp
Agro-forestry
Arable
Built
Campus
Ley
PP
Quarry
W ater
W oodland
Mapunit.shp
Field outlines from
aerial photograph
Land use from farm
records
Field identities
from older map

32. Maps as information sources:
conclusions
• All maps are inaccurate, they are models of
reality
• All maps miss out nearly all possible
information, but should display what you
need
• All maps are out of date, the world is
dynamic and changes
• Despite that, they are an indispensable
tool for conveying information about the
land.