nota gis kejiranan - week 11
TRANSCRIPT
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NeighbourhoodOperations
evaluate thecharacteristics ofan areasurrounding aspecific location.
e.g., identifyingproperties within500 m of a zonechangeapplicant:
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Analisis penampan (Buffers)
"neighbourhood" implies a relationship that
can be measured as a distance distance is a continuous variable
we naturally try to simplify distance: e.g.,
"inside or outside" , or "near or far"
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Buffer
a zone constructed outward from an object to
a specific distance commonly used in environmental regulation
to restrict activities too close to a natural
feature
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Setback
a zone constructed inward from an object to
a specific distance typically used to restrict building or activities
too close to the edge of a property parcel
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both buffers and setbacks imply a simple
zone: inside or outside the critical distance normally, a buffer or a setback is created as
a binary data set and used in an overlay to
mask out undesired areas for further
analyses
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Example: Salmon habitats vs. logging rights under the rules of exclusive ownership (pure capitalism) the owner of a
property has the right to extract the economic benefits of the land; a
logging company has the rights to remove any trees salmon return from the ocean to freshwater streams to spawn; their
reproduction depends on cold water temperatures and gravel streambottoms
removing the tree canopy near a stream can open the stream to directsunlight causing the water temperature to rise; vegetation removal can alsoincrease sediment flow in the streams, covering the gravel
government regulations have been enacted to restrict timber activities near
streams while permitting some economic benefit from the trees on the land buffers have been created within a certain distance around streams to
ensure shade and to provide enough undisturbed vegetation to trapsediment
the width of these buffers is strongly contested between the various parties
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Apa itu jiran?
Geometric Neighbours
e.g. Euclidean Distance: the distance from Point A to Point B is
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Jiran raster
neighbours are implicit in the grid
adjacent cells are either considered to be 4-connectedor 8-connected:
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Raster buffer creation:
measure Euclidean distances from a central cell draw buffer at selected distance
BUT! there is no
difference between a
2.0 and a 2.1 distance
neighbourhood
this effect decreases withdistance from target cell
and/or an increase in cell
resolution; buffer widths of
3 cell-widths or more
produce a reasonable
approximation
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it is easy to insert a barrier when measuring
raster distances; e.g. waterfalls on a canoemap
raster distances allow weights to be assigned
to each cell; e.g. steeper slopes will produce
faster ski runs
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Jiran vektor
by definition, topologcial neighbours are stored inthe database
geometric neighbours (i.e., distance) are harder toextract e.g., use an overlay operation to define a region of
interest neighbourhood
BUT! vector
representations
allow a search
radius or shape to
be of any size
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Vector buffer creation:
a circle is drawn around each vertex
a rectangle is drawn around each line segment
all of the circles and rectangles are aggregated to
remove duplicate areas
complex process generally hidden from the user
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neighbourhoods are most commonly square,
circular, or rectangular, but they need not beany regular shape, e.g. a country
search functions can be an equation: Select
hospitals with more than 500 beds and are
less than 5 years old