vector analysis 1

© Phil Hurvitz, 1999-2000

CFR 250/590 Introduction to GIS, Autumn 1999

vector_analysis_1.ppt 1

Vector Analysis I

Where have we come so far?

• What GIS is.

• How GIS works.

• Some of what GIS can do.

• GIS data formats.

• Spatial data.

• Tabular data.

• Modifying views of data.

By now, you should be familiar with:




Vector Analysis I

What comes next?




Vector Analysis I

Basic vector analysis

• Which forest stands lie within 100 m of a road?

• Which inventory plots have been affected by a recent slope failure?

• Does any stream pass through the oldest stands in a forested area?

• What is the age-class distribution of stands adjacent to stands younger than 10 years?

• What is the mean slope of the group of stands within 50 m of a stream?

Examples




Vector Analysis I

Overview of basic vector analysis

• Analyzing spatial relationships

• Theme-on-theme selection

• Selecting points near a line

• Selecting adjacent features

• Line-on-polygon selection

• Polygon-on-line selection

• Point-in-polygon selection

• Polygon-on-point selection

• Polygon-on-polygon selection

• Spatial join

• Spatial join: containment

• Spatial join: proximity

• Spatial merge




Vector Analysis I

Analyzing spatial relationships

• Proximity

• Containment

• Overlap

Relationships between features




Vector Analysis I

Theme-on-theme selection

• Definitions

• Target theme: the theme we want to know something about

• Selector theme: the theme we are spatially referencing to

• For a series of streams, find the distance to the nearest forest stand

target theme selector theme




Vector Analysis I

Theme-on-theme selection: feature type relationships




Vector Analysis I

gates near streams

Selecting points near a line (proximity)




Vector Analysis I

Selecting adjacent features (proximity of 0)

stands adjacent to other stands




Vector Analysis I

Line-on-polygon selection (intersection, proximity of 0, overlap)

roads and streams within stands




Vector Analysis I

Polygon-on-line selection (intersection, proximity of 0, overlap)

stands traversed by streams




Vector Analysis I

CFI plots within 30-40 y old stands

Point-in-polygon selection (containment)




Vector Analysis I

conifer basal area statistics

Point-in-polygon selection

30-40 year old stands are underrepresented in inventory




Vector Analysis I

Polygon-on-point selection

stands containing non-forestedor unsampled plots




Vector Analysis I

Polygon-on-polygon selection (containment, overlap)

stands overlapping with unstable soils




Vector Analysis I

Spatial join

• theme attribute tables are joined on the shape field

• features are related and compared for distance and containment




Vector Analysis I

Spatial join: containment

polygon attributes are attached to points

related fields can be used for display




Vector Analysis I

Spatial join: proximity

distance from plot centers to roads

distance used as a display field




Vector Analysis I

Spatial merge

• features with identical attribute values are merged together

• table records are joined

• a new theme is created

• a special case of the tabular summary




Vector Analysis I

Spatial merge

summarize the Age_Class_1999field

creates a new theme




Vector Analysis I

Spatial merge

multiple objects, one record

vector analysis 1

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