geo 265 - gis practicuum exercise 4 updating the city of corvallis chapter 8 of gis concepts and...
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Geo 265 - GIS Practicuum
Exercise 4Updating the City of Corvallis
Chapter 8 of GIS Concepts and ArcView Methods
Geo 265, GIS Practicuum
Introduction• New research park for new
companies
• Sunset Research Park, SW Corvallis
• 15 years of growth - GIS db needs update!
• CREATE NEW DATA - on-screen digitizing– Buildings, parking lots
Geo 265, GIS Practicuum
But wait !!
• New building regulations to project wetlands
• How far away are buildings from wetlands?– Do they fall within a BUFFER zone
Geo 265, GIS Practicuum
Exercise 4
1. On screen (“heads up”) digitizing
2. Buffering
3. Decision-making– Buildings on sensitive wetlands?
Geo 265, GIS Practicuum
Image DataDigital Orthophoto Quads
(DOQs)– aerial photographs– camera orientation, terrain– raster images at 1m resolution– 6m positional accuracy at scale
of 1:12,000 – Oregon Lambert projection
Geo 265, GIS Practicuum
New GIS Skills
• Adding and viewing images• Creating new shape files and adding
attribute information.• Using scripts• Downloading data from a web site• Uncompressing data
Geo 265, GIS Practicuum
Buffering
• Common operation when performing spatial analysis
• Use when you must identify the area surrounding geographic features– SPATIAL PROXIMITY
• Buffering generates new polygons around existing points, lines, or polygons
Geo 265, GIS Practicuum
Geo 265, GIS Practicuum
Geo 265, GIS Practicuum
Buffering Steps1) identify the THEME, the FEATURE
type, DISTANCE to be buffered
2) new theme of buffer polygons generated
3) overlap between buffer polygons removed
4) each polygon in resulting theme coded as being either “inside” or “outside” the buffer zone
Geo 265, GIS Practicuum
(1) Identify Themes, Features & Buffer Distance
Theme: RIVERFeature type: LINEBuffer distance: 75 ft
Theme: STORESFeature type: POINTBuffer distance: 200 m
Geo 265, GIS Practicuum
(2) New Polygon Buffers Created - New ThemesTheme: RIVERFeature type: LINEBuffer distance: 75 ft
Theme: STORESFeature type: POINTBuffer distance: 200 m
Geo 265, GIS Practicuum
(3) Overlap Between Buffer Polygons Removed (Ex. 0)
Theme: RIVERFeature type: LINEBuffer distance: 75 ft
Theme: STORESFeature type: POINTBuffer distance: 200 m
Geo 265, GIS Practicuum
(4) New Topology Built w/ Inside / Outside Polygons
Inside = 100Inside = 1 (Outside)
Inside
Outside(Inside=1)
Outside(Inside=1)
Geo 265, GIS Practicuum
Buffer Widths
uniform width
variable width
Geo 265, GIS Practicuum
Exercise 4 tips
• Save your ArcView project OFTEN!!!– Back up to Zip disk or CD!!
• Carefully follow “What to Turn In” section
• Due to Janine by Friday, 10/24/03– Check open lab hours
Geo 265, GIS Practicuum