Spatial Analysis [1]

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Spatial Analysis [1]

Dr. Ragab Khalil

Department of Landscape Architecture Faculty of Environmental Design King AbdulAziz University Room 103

LA561 Computer Applications in LA LA561 Computer Applications in LA (GIS) (GIS)

Dr. Ragab Khalil KAAU - FED – LA561: GIS 2/34

Where have we come so far?

• By now, you should be familiar with:

What GIS is

How GIS works

Some of what GIS can do

GIS data formats Spatial data Tabular data

Modifying views of data

Basic operations on data entry and editing

What comes next?

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Dr. Ragab Khalil KAAU - FED – LA561: GIS 4/34

Basic vector analysis Basic vector analysis

• One of the most basic analytical tasks in a GIS is locating features in one layer based on the location of other features in the same layer or in another layer.

• Examples :

Which city lie within 10 km of a river?

Which sampling plots have been covered by a recent slope failure?

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

…

Dr. Ragab Khalil KAAU - FED – LA561: GIS 5/34

Basic vector analysis Basic vector analysis

• Examples:

What is the age of buildings adjacent to buildings younger than 10 years?

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

Dr. Ragab Khalil KAAU - FED – LA561: GIS 6/34

Basic vector analysis Basic vector analysis Overview

Overview

• Analyzing spatial relationships

Select by location (Layer-on-Layer selection)

Spatial join

Other spatial relationships will be

investigated in next lesson

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Dr. Ragab Khalil KAAU - FED – LA561: GIS 7/34

Analyzing spatial relationships Analyzing spatial relationships

• Relationships between features

Proximity

Containment

Overlap

• All based on feature geometry

Dr. Ragab Khalil KAAU - FED – LA561: GIS 8/34

Select by location Select by location

• Layer-on-layer selection

Selecting points near a line (proximity)

Selecting adjacent features (proximity)

Line-on-polygon selection (containment)

Polygon-on-line selection (overlap)

Point-in-polygon selection (containment)

Polygon-on-point selection (overlap)

Polygon-on-polygon selection (overlap)

Layer

Layer- -on on- -layer selection layer selection

• Selecting points near a line (proximity)

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Layer

• Selecting adjacent features (proximity)

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Layer

• Selecting adjacent features (proximity)

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Layer

• Line-on-polygon selection (containment)

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Layer

• Polygon-on-line selection (overlap)

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Layer

• Point-in-polygon selection (containment)

Layer

• Polygon-on-point selection (overlap)

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Layer

• Polygon-on-polygon selection (overlap)

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Layer

• Definitions

Target layer(s):

the layer(s) we want to know something about

Selector layer:

the layer we are spatially referencing to

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

selector layer

Dr. Ragab Khalil KAAU - FED – LA561: GIS 18/34

Layer

Layer- -on on- -layer selection : feature type layer selection : feature type relationships

relationships

• Spatial relationships follow geometric rules

point line polygon point

line polygon selects target layer features

that are within a given distance of selector layer features are within distance of

line polygon point

that intersect selector layer features intersect

point line polygon polygon

selects target layer features which contain the centers of selector layer features contain the center of

polygon point

whose centers fall inside selector layer features have their center in

point line polygon polygon

selects target layer features that completely contain selector layer features completely contain

polygon point

that are completely within selector layer features are completely within

selector layer feature types target layer

feature types purpose

spatial relationship

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Dr. Ragab Khalil KAAU - FED – LA561: GIS 19/34

Selecting points near a line (proximity) Selecting points near a line (proximity)

• Find inventory plots near streams

selector layer

target layer

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Selecting adjacent features

Selecting adjacent features (proximity of 0) (proximity of 0)

• Find stands adjacent to other stands

Line- Line -on on- -polygon selection polygon selection

(intersection, proximity of 0, overlap) (intersection, proximity of 0, overlap)

• Streams within stands

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• Stands traversed by roads Polygon

Polygon- -on on- -line selection line selection

(intersection, proximity of 0, overlap) (intersection, proximity of 0, overlap)

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Point

Point- -in in- -polygon selection (containment) polygon selection (containment)

• CFI plots within moderate to high windthrow potential soils

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Point

Point- -in in- -polygon selection (containment) polygon selection (containment)

• CFI plots within moderate to high windthrow

potential soils

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Spatial join Spatial join

• Spatial join

Spatial join: containment

Spatial join: proximity

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Spatial join Spatial join

• Layers are joined based on geometry

Features are related and compared for distance and containment

Based on feature geometry

Spatial join Spatial join

Not applicable Not applicable

A join point is matched to a target point at the same location.

Point Point

IS_WITHIN CONTAINS

INTERSECTS Join features

Target feature

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Spatial join Spatial join

A join polygon is matched to a target line that is inside the boundary of the join polygon Not applicable

A join polygon is matched to a target line that it intersects.

Polygon Line

A join line is matched to a target line that falls completely within the join line. Here the target line is coincident with the join line.

A join line is matched to a target line that completely contains it. Here the join line is coincident with the target line.

A join line is matched to a target line that it intersects. This includes lines that cross or are coincident.

Line Line

Not applicable A join point is

matched to a target line that contains it.

A join point is matched to a target line that it intersects.

Point Line

IS_WITHIN CONTAINS

INTERSECTS Join

Target

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Spatial join Spatial join

IS_WITHIN CONTAINS

INTERSECTS Join

Target

A join polygon is matched to a target polygon that is inside the boundary of the join polygon.

A join polygon is matched to a target polygon that contains it.

A join polygon is matched to a target polygon that it intersects or is inside of.

Polygon Polygon

Not applicable A join line is

matched to a target polygon that contains it.

A join line is matched to a target polygon that it intersects or is inside of.

Line Polygon

Not applicable A join point is

matched to a target polygon that contains it.

A join point is matched to a target polygon that it intersects or in inside of.

Point Polygon

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Spatial join Spatial join

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Spatial join Spatial join

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Spatial join: containment Spatial join: containment

• Records are joined for features within other features

• polygon attributes are

attached to points

• related fields can be used for display

Spatial join: proximity Spatial join: proximity

• Appends tables and automatically adds

distance field distance from each plot center point

to the closest road line

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Summary Summary

• Select by location

• Spatial join