Vector data input and editing Scanning (scan digitizing) –drum scanner scanner scans in map image...
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Transcript of Vector data input and editing Scanning (scan digitizing) –drum scanner scanner scans in map image...
Vector data input and editing
• Scanning (scan digitizing)
– drum scanner scanner scans in map image– specialized software ‘extracts’ point, line, and
area features– very expensive and susceptable to errors when
map is ‘dirty’
Vector data input and editing
• Digitizers are usually electromagnetic
• .01 inch resolution
• accuracy +/- .002 inches over 42 x 60 inch area
• operator error is typically greater than hardware accuracy
Vector data input and editing
Digitizing Process:
• prepare map sheet
• digitize the coverage
• identify and correct digitizing errors
• build topology
• identify and correct topology errors
• assign attributes
• identify and correct attribute errors
Vector data input and editing
Map preparation
Map quality?
Separations?
Folds and wrinkles in the map?
Transfer to mylar ?
Vector data input and editing
• Digitizing– parameters
• fuzzy tolerance • maximum number of shape points per feature
– process• try to capture the necessary accuracy with least amount
of shape points
• Build topology• Documentation of metadata
Vector data input and editing
• Editing of vector digitizing errors
– entity error (positional error)– attribute error– entity-attribute error
Vector data input and editing
• Editing of positional errors– undershoots/overshoots (dangling nodes)– open polygon– missing nodes (weird polygons)– pseudonodes– polygon label errors (missing/too many)– sliver polygons
Vector data input and editing• Vector editing
– open polygon – undershoots/overshoots (dangling nodes)