GUS: 0262 Fundamentals of GIS

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GUS 0262Fundamentals of GIS

• Lecture Presentation 5
• Vector Operations
• Jeremy Mennis
• Department of Geography and Urban Studies
• Temple University

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Measurement
Length (Lines) by Pythagorean theorem Area
(Polygons) by dividing the polygon into
triangles whose areas can easily be calculated
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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
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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
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Buffer
Definition of what is within/without a given
proximity
Line buffer
Point buffer
Polygon buffer
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Doughnut Buffer
e.g. within 10 meters but not within 5 meters
Buffer polygon
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10
Hole
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Variable Buffer
Buffer distance varies by some feature attribute
or friction surface
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Variable Buffer
B
ID Dist A 3 B 2 C 5
A
Original line
C
4
6
10
Buffer polygon
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Overlay
A series of registered data layers overlaying
each other
Arguably the most important GIS analysis function
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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
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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)
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Point in Polygon Overlay
Land Cover
Trees
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
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Line in Polygon Overlay
Land Cover
Streets
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
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Polygon Overlay
Intersection (and)
Union (or)
Identity
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Polygon Overlay Intersection
Agriculture
Land Cover
ltIntermediategt
A
A
B
B
ID Owner A Brown B Smith
ID Cover A commercial B industrial
Area of intersection
New node
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Polygon Overlay Intersection
Output
ltIntermediategt
A
B
ID Owner Cover A Brown commercial B
Smith industrial
Area of intersection
New node
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Polygon Overlay Union
Agriculture
ltIntermediategt
Land Cover
A
A
B
B
ID Owner A Brown B Smith
ID Cover A commercial B industrial
Area of union
New node
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Polygon Overlay Union
Output
ltIntermediategt
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
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Polygon Overlay Identity
Agriculture (input layer)
Land Cover (identity layer)
ltIntermediategt
A
A
B
B
ID Owner A Brown B Smith
ID Cover A commercial B industrial
Area of identity
New node
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Polygon Overlay Identity
Output
ltIntermediategt
A
B
C
D
ID Owner Cover A Brown commercial B
Brown C Smith
D Smith industrial
Area of identity
New node