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

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

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

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

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

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

Variable Buffer Buffer distance varies by some feature attribute or friction surface

Variable Buffer Buffer polygon A B C ID Dist A 3 B 2 C Original line

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

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

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)

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

Line in Polygon Overlay A B C ID Street A Race B Race C Arch Line Table ID Street Cover A Race Rural B Race Urban C Arch Urban D Race Urban Line Table ID Cover 1 Rural 2 Urban Poly Table 12 += Land CoverStreetsNewStreets A B C D

Polygon Overlay Intersection (and)Union (or) Identity

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

Polygon Overlay: Intersection Output ID Owner Cover A Brown commercial B Smith industrial A B Area of intersection New node

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

Polygon Overlay: Union Area of union New node Output ID Owner Cover A commercial B Brown commercial C Brown D Smith E Smith industrial A BC DE

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

Polygon Overlay: Identity Area of identity New node Output ID Owner Cover A Brown commercial B Brown C Smith D Smith industrial AB CD