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GUS: 0262 Fundamentals of GIS

GUS: 0262 Fundamentals of GIS. Lecture Presentation 5: Vector Operations Jeremy Mennis Department of Geography and Urban Studies Temple University. 1. D. 2. Measurement. Length (Lines) by Pythagorean theorem Area (Polygons)

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GUS: 0262 Fundamentals of GIS

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  1. GUS: 0262Fundamentals of GIS Lecture Presentation 5: Vector Operations Jeremy Mennis Department of Geography and Urban Studies Temple University

  2. 1 D 2 Measurement Length (Lines) by Pythagorean theorem Area (Polygons) by dividing the polygon into triangles whose areas can easily be calculated

  3. Classification An example classification: Anderson Land Cover classification (Anderson et al., 1976) 1 urban or built-up 2 agricultural 3 rangeland 4 forest ... 9 41 deciduous forest 42 evergreen forest 43 mixed forest

  4. Classification Line Dissolve (Map Dissolve) 2 3 1 2 1 4 1 grain crops 2 orchards 3 residential 4 commercial 1 agricultural 2 non-agricultural

  5. Buffer Definition of what is within/without a given proximity Line buffer Point buffer Polygon buffer

  6. Doughnut Buffer • e.g. within 10 meters but not within 5 meters Buffer polygon 5 10 ‘Hole’

  7. Variable Buffer • Buffer distance varies by some feature attribute or friction surface

  8. Variable Buffer ID Dist A 3 B 2 C 5 B A Original line C 4 6 10 Buffer polygon

  9. Overlay A series of registered data layers ‘overlaying’ each other Arguably the most important GIS analysis function

  10. Overlay Derived from manual cartographic overlay using Mylar sheets (transparent plastic) that were physically overlaid on top of one another. -Ian McHarg in landscape architecture at University of PA

  11. Overlay • An overlay operation takes two or more data layers as input and results in an output data layer • Three types of overlay: • Point in polygon • Line in polygon • Polygon (polygon on polygon)

  12. Point in Polygon Overlay Trees Land Cover NewTrees 1 2 A A C + = C B B Point Table Poly Table Point Table ID Cover 1 Rural 2 Urban ID Tree A Elm B Maple C Elm ID Tree Cover A Elm Rural B Maple Rural C Elm Urban

  13. Line in Polygon Overlay Streets Land Cover NewStreets C C A A + = D B B 1 2 Line Table Poly Table Line Table ID Cover 1 Rural 2 Urban ID Street A Race B Race C Arch ID Street Cover A Race Rural B Race Urban C Arch Urban D Race Urban

  14. Polygon Overlay Intersection (and) Union (or) Identity

  15. Polygon Overlay: Intersection Agriculture Land Cover <Intermediate> A A B B ID Owner A Brown B Smith ID Cover A commercial B industrial Area of intersection New node

  16. Polygon Overlay: Intersection <Intermediate> Output A B ID Owner Cover A Brown commercial B Smith industrial Area of intersection New node

  17. Polygon Overlay: Union Agriculture Land Cover <Intermediate> A A B B ID Owner A Brown B Smith ID Cover A commercial B industrial Area of union New node

  18. Output Polygon Overlay: Union <Intermediate> B C A D E ID Owner Cover A commercial B Brown commercial C Brown D Smith E Smith industrial Area of union New node

  19. Polygon Overlay: Identity Agriculture (input layer) Land Cover (identity layer) <Intermediate> A A B B ID Owner A Brown B Smith ID Cover A commercial B industrial Area of identity New node

  20. Polygon Overlay: Identity Output <Intermediate> A B C D ID Owner Cover A Brown commercial B Brown C Smith D Smith industrial Area of identity New node

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