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1106: Geographical Information: a primer

1106: Geographical Information: a primer. Communicating with Cartography 29/10/2004. TOPICS. How does a map communicate? Thematic maps Topographic information Abstract maps Geographical Information Systems Practical info for NEXT WEEK. How does a map communicate?.

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1106: Geographical Information: a primer

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  1. 1106: Geographical Information: a primer Communicating with Cartography 29/10/2004

  2. TOPICS • How does a map communicate? • Thematic maps • Topographic information • Abstract maps • Geographical Information Systems • Practical info for NEXT WEEK

  3. How does a map communicate? • Real word features are represented as points, lines, polygons, contours and symbols • A map conveys a wide range of characteristics about the real world • Size, length, distribution, patterns, contiguity, neighbourhood, space, shape and orientation

  4. Thematic maps • Perhaps we should say - What do maps communicate? • Thematic means theme based and a map can graphically communicate the spatial variability in a wide range of possible themes - both human (socio-economic) and physical

  5. Thematic Maps • Population, death-rate, income levels etc are dynamic themes of data that will change rapidly • Soils, geology, ecological zones and political maps will remain fairly static • Themes may be presented as different colours or dots/shading - or even small pie-charts overlaid onto a normal political map

  6. Topographic maps • Contours show areas of equal height above mean sea-level (MSL) • Contours close together represent steep changes in height - contours far apart show gradual change in height • Contours use an interval (in metres) although not all contours may be labelled

  7. Using contour maps • Locate the nearest line to your feature • If not labelled, locate nearest labelled line and multiply number of contours away by the interval then add (or subtract) this value from the nearest labelled contour value • An alternative to using contours is a 3-dimensional rendering of the surface

  8. Abstract Maps • Maps do not always have to be accurate in terms of their representation of reality • Maps can be abstract and may represent features of the real world in an ethereal way • Maps can be used to suggest connections, principles or ideas that bear no parallel in reality. Such en entity is known as a cartogram

  9. Abstract maps • Any kind of information can be communicated by a map • Just as the London Underground was designed by an electronics draughtsman (Beck) in the 1920s, maps can be used to show power distribution - using clever abstraction and use of symbols

  10. Abstract maps • Maps can also be used to provide a graphical representation of forecasts • A map of a forecast variable (rainfall or temperature) is interesting as no such feature actually exists in reality.

  11. Abstract Maps • Maps do not have to be 2 dimensional • Detailed surveys of towns and cities have allowed computer generated 3-dimensional renderings to be generated

  12. GIS • Geographical Information System (GIS) • A GIS allows layers of spatially referenced information to be combined as though they were transparent slides • A GIS can drill down through these layers to perform calculation, scenarios and model solutions to complex problems

  13. GIS • A GIS must have a spatial reference framework. This can be latitude/longitude, Ordnance Survey grid, postcodes etc • A GIS operates entirely within a computer system • VECTOR features are represented as POINTS, LINES and POLYGONS

  14. GIS • Some map data is continuous and is created from pixels. This type of data is known as RASTER data • Raster data can be derived from satellite (rainfall, vegetation or a an aerial photograph) • Raster data can be used in complex environmental models

  15. GIS • Can be used for real-time applications • Vector data stores metadata relating to any conceivable statistic in a separate database file that is spatially referenced within the map • Raster data encodes continuous data as pixel values for a range of remotely sensed information

  16. Suggested Reading • Mapping: ways of representing the world by Dorling and Fairbairn, 1997 • ESRI map book. Implementing concepts of Geography. Volume 14, 1999 • Getting started with Geographical Information Systems by Clarke K., 1997

  17. PRACTICAL: Today Groups A2, B1 & B2 (2pm – 3:30pm) A1, C1 & C2 (3:30pm – 5pm) Loxford: L106

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