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Geographic Information Systems

Geographic Information Systems. Session 2: What you absolutely need to know about spatial data. Karl Hennermann School of Environment and Development. Contents. Defining GIS The world is a set of layers Vectors and rasters – representing real world features

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Geographic Information Systems

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  1. Geographic Information Systems Session 2: What you absolutely need to know about spatial data Karl Hennermann School of Environment and Development

  2. Contents • Defining GIS • The world is a set of layers • Vectors and rasters – representing real world features • Where am I? Coordinate systems • Making maps: cartographic projections • Challenges and constraints for GIS • Q&A Karl Hennermann, 13-03-2013

  3. Contents • Defining GIS • The world is a set of layers • Vectors and rasters – representing real world features • Where am I? Coordinate systems • Making maps: cartographic projections • Challenges and constraints for GIS • Q&A Karl Hennermann, 13-03-2013

  4. Defining GIS GIS is not a software product. Karl Hennermann, 13-03-2013

  5. Definition I: GIS is… A computer system capable of holding and using data on geographical objects ESRI (1997): Understanding GIS. The ARC/INFO method. Karl Hennermann, 13-03-2013

  6. “... geographical objects” Karl Hennermann, 13-03-2013

  7. “...data on geographical objects” Location, location, location Karl Hennermann, 13-03-2013

  8. “...data on geographical objects” School locations Flooded area (-324072;1667468), (322317;1665019), (-321993;1661876), (-323010;1660028), (-324211;1659751), (-324396;1660305) Karl Hennermann, 13-03-2013

  9. Definition I: GIS is… A computer system capable of holding and using data on geographical objects ESRI (1997): Understanding GIS. The ARC/INFO method. Karl Hennermann, 13-03-2013

  10. Definition II: GIS is… An organised collection of computer hardware, software, geographical data, and personnel designed to efficiently capture, store, update, manipulate, analyse, and display all forms of spatially referenced information. ESRI (1997): Understanding GIS. The ARC/INFO method. Karl Hennermann, 13-03-2013

  11. “...hardware, software, geographical data, and personnel to capture, store, update, manipulate, analyse, and display...“ Architecture view Process view • Hardware • Personnel & Skills • Software • Geospatial data Karl Hennermann, 13-03-2013

  12. So, what is GIS about? • GIS is not a software product. • GIS is about the methods / techniques of analysing data spatially or geographically • You do not have to use GIS software for work to count as geographical analysis • The software simply allows these methods to be carried out efficiently Karl Hennermann, 13-03-2013

  13. Contents • Defining GIS • The world is a set of layers • Describing the real world - vectors and rasters • Where am I? Coordinate systems • Making maps: cartographic projections • Challenges and constraints for GIS • Q&A Karl Hennermann, 13-03-2013

  14. The world is a set of layers Jones, Christopher (1997): Geographical Information Systems and Computer Cartography. Addison Wesley Longman.p30 Karl Hennermann, 13-03-2013

  15. Contents • Defining GIS • The world is a set of layers • Describing the real world - vectors and rasters • Where am I? Coordinate systems • Making maps: cartographic projections • Challenges and constraints for GIS • Q&A Karl Hennermann, 13-03-2013

  16. Describing the real world - vectors File 18 34 Image (c) Google 14 22 44 Karl Hennermann, 13-03-2013 15 3 85 17

  17. Describing the real world - vectors Land use (Polygon) Roads (Polyline) Bus stops (Point) Image (c) Google Karl Hennermann, 13-03-2013

  18. Describing the real world - rasters Logical Data Model 1: Green space 2: Water body 3: Residential 4: Industrial 5: ... File 32 512125 5317265 100 100 1,1,1,1,1,1,2,1,1,1, 1,1,4,4,1,1,2,1,1,1, 4,4,4,4,1,2,1,1,1,1, 4,1,1,1,2,1,3,1,1,1, 4,4,4,2,1,3,3,3,1,1, 3,3,4,2,1,3,3,3,3,1, 3,3,2,4,4,3,3,3,3,3, 3,2,4,4,4,3,3,3,3,3, 2,4,4,4,4,3,3,3,3,3, EOF Image (c) Google Karl Hennermann, 13-03-2013

  19. Contents • Defining GIS • The world is a set of layers • Describing the real world - vectors and rasters • Where am I? Coordinate systems • Making maps: cartographic projections • Challenges and constraints for GIS • Q&A Karl Hennermann, 13-03-2013

  20. Geographic Coordinate Systems(use on spheres and with GPS) The most common geographic coordinate system is: Decimal Degrees on WGS 1984 The Measurement Units (almost always DD) The Geodetic Datum In the UK also Decimal Degrees on OSGB 1936 Karl Hennermann, 13-03-2013

  21. Contents • Defining GIS • The world is a set of layers • Describing the real world - vectors and rasters • Where am I? Coordinate systems • Making maps: cartographic projections • Challenges and constraints for GIS • Q&A Karl Hennermann, 13-03-2013

  22. Making maps: cartographic projections A method by which the curved surface of the earth is portrayed on a flat surface. This generally requires a systematic mathematical transformation of the earth's graticule of lines of longitude and latitude onto a plane. ESRI (2010): ArcGIS Desktop Glossary Karl Hennermann, 13-03-2013

  23. Making maps: cartographic projections Transverse Mercator + + + + + Karl Hennermann, 13-03-2013

  24. Making maps: cartographic projections The Transverse Mercator projection Snyder, John P. (1987), Map Projections – A Working Manual. U.S. Geological Survey Professional Paper 1395. Washington. Karl Hennermann, 13-03-2013

  25. Making maps: cartographic projections There are hundreds of geographic coordinate systems, projections, and projected coordinate systems. Always know what the coordinate system and projection of your data is. How to make the British National Grid: Take a spheroid with the OSGB 1936 spec and project it with Transverse Mercator, using the Greenwich meridian as Central Meridian. Then overlay a projected coordinate system, measuring in meters North and East from the Isles of Scilly. Karl Hennermann, 13-03-2013

  26. Easting: 411000 (meters east of the reference point) Projected Coordinate Systems(use on maps) 411000 412000 413000 • British National Grid: • Units: meters • Reference point is SW of Isles of Scilly 1000m 409000 Northing: 409000 (meters north of the reference point) 408000 Karl Hennermann, 13-03-2013

  27. Contents • Defining GIS • The world is a set of layers • Describing the real world - vectors and rasters • Where am I? Coordinate systems • Making maps: cartographic projections • Challenges and constraints for GIS • Q&A Karl Hennermann, 13-03-2013

  28. Challenges and Constraints Challenges and constraints • Data • Data • Data • Cost, arguing that it pays off, and defining business processes • Multiplication of effort, Interoperability, SDIs Karl Hennermann, 13-03-2013

  29. Further reading • Paul Longley, Mike Goodchild, David Maguire, David W. Rhind (2010): Geographic Information Systems and Science. 3rd Ed. John Wiley & Sons • Ian Heywood, Sarah Cornelius, Steve Carver (2011): An Introduction to Geographical Information Systems. 4thEd., Prentice Hall Karl Hennermann, 13-03-2013

  30. Thank you Karl Hennermann, 13-03-2013

  31. Q&A Karl Hennermann, 13-03-2013

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