Geo GIS Practicuum Exercise 4 Updating 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 Data Digital 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

Buffering Steps 1)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: RIVER Feature type: LINE Buffer distance: 75 ft Theme: STORES Feature type: POINT Buffer distance: 200 m

Geo 265, GIS Practicuum (2) New Polygon Buffers Created - New Themes Theme: RIVER Feature type: LINE Buffer distance: 75 ft Theme: STORES Feature type: POINT Buffer distance: 200 m

Geo 265, GIS Practicuum (3) Overlap Between Buffer Polygons Removed (Ex. 0) Theme: RIVER Feature type: LINE Buffer distance: 75 ft Theme: STORES Feature type: POINT Buffer distance: 200 m

Geo 265, GIS Practicuum (4) New Topology Built w/ Inside / Outside Polygons Inside = 100 Inside = 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