geo 265 - gis practicuum exercise 4 updating the city of corvallis chapter 8 of gis concepts and...

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