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EA141 Module 7

EA141 Module 7. Geographic Information Systems GIS. 7.1 Information Systems. collection of raw data processed to produce useful information Steps observation collection processing (analysis) results decisions. e.g. test marks. 7.2 Geographic Information Systems.

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EA141 Module 7

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  1. EA141 Module 7 Geographic Information Systems GIS

  2. 7.1 Information Systems • collection of raw data • processed • to produce useful information • Steps • observation • collection • processing (analysis) • results • decisions e.g. test marks

  3. 7.2 Geographic Information Systems • geographic data = location (x,y,z,t) of: • people • places • things • all info in a GIS must be geographically refererenced • temporal referencing much more difficult! • processing = spatial analysis

  4. 7.2 GIS vs. IS • e.g. where to locate a new donut shop? • I.S. … how many donut shops there are in Hamilton • G.I.S. … draw me a map showing location of all donut shops in Hamilton • GIS uses "spatial analysis" to produce a "smart map" • most things we do in GIS could be done with paper maps (dumb maps)… • but GIS makes it a lot easier • time = $$$ … GIS makes new analyses feasible

  5. 7.3 GIS and Surveying • GIS  new data acquisition • GIS relies on accurate data • Surveying = new data acquisition • other fields of Geomatics also contribute: • GPS • photogrammetry • remote sensing

  6. 7.4 What's it made of? • GIS = • hardware (computer, printer, etc.) • software (MapInfo, ArcInfo, ArcView) • data • approx. $$cost$$ breakdown: • hardware 10-20% • software 10-20% • data 60-80% • data acquisition • data entry • data scrubbing

  7. 7.5 Spatial Data • all natural or man-made features • lines or symbols on maps • images on photos • "spatial object" = digital representation of real-world "entity" • dimensionality… • 0-D = (x,y,z) = "point data" • 1-D = set of point data = "line data" • 2-D = closed sets of lines = "area data" • 3-D = "volume data"

  8. 7.5 Spatial Data - Dimensionality • 0-D = (x,y,z) = "point data" = position only • e.g. manhole • traffic light • well • donut shop • 1-D = set of point data = "line data" • e.g. roads • sewers • property lines • stream

  9. 7.5 Spatial Data - Dimensionality • 2-D = closed sets of lines = "area data" • e.g., building footprint • park • wooded area • land zoned "commercial" • 3-D = "volume data" • e.g., gravel quarry • cut/fill area • oil/gas deposit

  10. 7.5 NON-Spatial Data • a.k.a. "attribute data" = any other characteristics that pertain to an entity • e.g. ownership • soil type • age of structure • material • e.g. water well • spatial data = point data = 0-D = location • non-spatial data = owner's name, drill date, depth, etc.

  11. 7.6 Data Models • what data needs to be included in the GIS? • depends on end-uses • depends on budget $$$ • two types of data models • Raster (dumb) = 0-D • Vector (smart) = 1-D to 3-D

  12. 7.7 Topology • branch of math describing relationships between spatial objects • topological relation may be: • connectivity (connected to another object) • directionality (before or after another object) • adjacency (beside another object) • nestedness (inside another object)

  13. 7.8 Analysis - Buffering • common analytical function of GISs • area around an object • think of AutoCAD "OFFSET" command • point buffer = area around a point • line buffer = area left & right of a line • polygon buffer = area around area

  14. 7.8 Other Analyses • adjacency • e.g. find neighbouring properties • connectivity • e.g. find connected watermains, streets to evaluate emergency preparedness • overlay • MOST COMMON ANALYSIS • e.g. show all properties: • with no vegetation • slope < 5% • on clay soil • < 15 min from a donut shop 

  15. 7.9 GIS & GPS • GPS gives current location of mobile things • GIS knows locations of fixed features • GIS + GPS tells me: • what route will minimize time • application to emergency vehicles, police • best route from where I am to a donut shop when visiting a new city  • "the only limit is our imagination"…

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