1017 Maps and mapping
- 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.