Maps and mapping
Spatial models of the real World:
Traditional paper maps
Why do we need models?
The real World is too complex to
manage in its entirety. Models
give us a simple manageable
represe...
Maps: what they are, what they show
• Map: a representation, by graphical means,
of selected features of the Earth
– A map...
Maps: what they are, what they show
• Map: a representation, by graphical means,
of selected features of the Earth
– A map...
Maps: what they are, what they show
• Map: a representation, by graphical means,
of selected features of the Earth
– A map...
Coates Farm, map of selected features:
simplified detail, shown by line and text symbols
Coates Farm, 1:50,000 Ordnance Survey map:
different detail, shown by point, line, area and text symbols
Map symbols
colour and texture also used
Manor Farm
Point: towns, buildings, sample points
Line: roads, streams, boundarie...
Map symbols example:
D.R. of the Congo (formerly Zaire)
Town locations:
points
Key to symbols
given in the
“legend”
Lakes ...
Problems with mapping
The Earth is a spheroid and maps are flat
– map projections
The Earth is huge and maps are tiny
– sc...
Map projections:
flattening out the curved Earth
Map projections:
flattening out the curved Earth
Map projections:
flattening out the curved Earth
Three mathematical projection examples
Three mathematical projection examples
Three mathematical projection examples
Three different projections
same place
An interrupted projection:
distortions concentrated into “unimportant areas”
Problems with projections
They always distort one or more of:
– distance
– area
– shape
– direction (angle)
Type of projec...
Scale reduction
Drawing a big World on small paper
Mathematical reduction. 1:1000
– 1 unit on map = 1000 of the same unit ...
Scale reduction
Drawing a big World on small paper
Mathematical reduction. 1:1000
– 1 unit on map = 1000 of the same unit ...
Same place, different map scale
Defining position: co-ordinate systems
How do you say where something is?
– Description: “five miles beyond the hump back
...
Geographical co-ordinates
Latitude and longitude
Grid co-ordinates;
applied to a projected map
Base map projected
using a “Universal
transverse mercator”
(UTM) projection....
Creating your own map
Basic principles of map creation:
– Forecast the end users’ needs
– Select the features to be shown
...
Forecast
• Decide who is going to use your map and
what they will use it for
• Define the geographic extent of their area ...
Compile mapping data and select what you need
Existing
maps
Compile mapping data and select what you need
Existing
maps
Aerial photos
Compile mapping data and select what you need
Existing
maps
Aerial photos
Farm records
The new land use map:
data selected, simplified and symbolised
Mapunit.shp
Agro-forestry
Arable
Built
Campus
Ley
PP
Quarry...
Maps as information sources:
conclusions
• All maps are inaccurate, they are models of
reality
• All maps miss out nearly ...
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1017 Maps and mapping

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1017 Maps and mapping

  1. 1. Maps and mapping Spatial models of the real World: Traditional paper maps
  2. 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. 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. 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. 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. 6. Coates Farm, map of selected features: simplified detail, shown by line and text symbols
  7. 7. Coates Farm, 1:50,000 Ordnance Survey map: different detail, shown by point, line, area and text symbols
  8. 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. 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. 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. 11. Map projections: flattening out the curved Earth
  12. 12. Map projections: flattening out the curved Earth
  13. 13. Map projections: flattening out the curved Earth
  14. 14. Three mathematical projection examples
  15. 15. Three mathematical projection examples
  16. 16. Three mathematical projection examples
  17. 17. Three different projections same place
  18. 18. An interrupted projection: distortions concentrated into “unimportant areas”
  19. 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. 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. 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. 22. Same place, different map scale
  23. 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. 24. Geographical co-ordinates Latitude and longitude
  25. 25. Grid co-ordinates; applied to a projected map Base map projected using a “Universal transverse mercator” (UTM) projection. Grid laid over map.
  26. 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. 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. 28. Compile mapping data and select what you need Existing maps
  29. 29. Compile mapping data and select what you need Existing maps Aerial photos
  30. 30. Compile mapping data and select what you need Existing maps Aerial photos Farm records
  31. 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. 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.

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