lecture 4. digitization
DESCRIPTION
pdfTRANSCRIPT
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DIGITIZATION
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Outline
Digitizing overview
GIS features
Digitizing features
Advanced digitizing tools
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DIGITIZING OVERVIEW
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Why digitize?
New maps
Map features are wrong
Missing features
Other?
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Digitizing tablets Used to digitize hard
copy maps into GIS
Transform wire intersections into
coordinates of the
tablets coordinate system
Heads down digitizing
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Steps for heads down digitizing Tape map to the
digitizer
Register control points
on the map
Estimate two
conversion equations
(one for vertical and
one for horizontal
coordinates)
Digitize vectors (points,
lines, or polygons)
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Control
points
Map
Puck
Tape
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Heads up digitizing
Mouse on a screen
Digitizes paper maps, aerial photos, or other
images
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GIS FEATURES
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Points
Single features
Nodes Line endpoints
Vertex points Controls shapes of lines
and polygons
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Creating points
Heads up digitizing
Single point features
Sketch tool and snapping features
Points added as XY event files
Points geocoded using addresses
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Lines
Starting and ending points with shape
vertices as needed
Vertex points
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Lines
Physical attributes of TIGER streets
Shape
From and To attributes Node
Address
Lat/long
Length
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Polygons
Three or more lines joined to form a closed
area
Single polygons or multipart features
(Hawaiian islands can be multiple polygons as one feature)
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Polygons
Physical attributes
Shape
Area
Perimeter
Length
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