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Analysis I: Selection

And an introduction to planning an analysis

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Topics

• Selection and its booby traps• A Project• Demo

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Selection

• Three ways to select…– Manual using the tool– Select by Attribute– Select by Location

• Booby Trap

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Nitty-Gritty

• Limiting what can be selected• Set it in Selection TOC tab• Or• In Selection menu / Set Selectable

Layers• This is good practice because• Doing this prevent you from

selecting the wrong layer

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Select by AttributeRight Layer?List only selectable FCsKind of selectionFields in layer

Operation

SQL statement

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Booby Traps

• Not selecting from right layer• Not paying attention to the

selection process– Create New Selection– Add to the current selection– Remove from the current selection– Select from the current selection

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Select by Attribute

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Select from current selection

• Still Tax Parcels• But I want only

those parcels that area >4.9 acresa

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Select by Location

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Analysis Options: Location

• Intersect• Are within a distance of• Completely Contain• Are completely within• Have their centroid in• Touch the boundary of• Share a line segment with• Are identical to• Are crossed by the outline of• Contain• Are contained by

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Options: Intersect

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Options:Touch Bndy of…

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Options: Have their Center in…

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Options: Are completely w/in…

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Options: w/in a distance of…

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Options: are contained by…

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Options: are contained by…

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The Problem• Ripemoff Power Co needs to…

– Find areas where, in Martinsburg, Willow can be grown and harvested with farm types of machinery

– The requirements are…

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TaxParcel Requirements

• Land USE must be Ag..• Land Cover must be

Ag• Slope in the parcel . . .

must be everywhere less than or equal to 8%.

• Tax parcels must be . . 50 acres or more

• No wetlands• No ponds

.. Tax Parcel data [CLS]

.. Landsat data [grid code]

.. Slope from DEM & processed into poly shape

.. TaxParcel data [acres]

… MartDECwet…Ponds

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TaxParcel Requirements

• Land USE must be Ag..• Land Cover must be

Ag• Slope in the parcel . . .

must be everywhere less than or equal to 8%.

• Tax parcels must be . . 50 acres or more

• No wetlands• No ponds

.. Select by Attribute

.. Select by Attribute

.. Complex raster processing

.. Select by Attribute

… Select by location…Select by location

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TaxParcel Requirements• Land USE must be Ag..• Land Cover must be

Ag• Slope in the parcel . . .

must be everywhere less than or equal to 8%.

• Tax parcels must be . . 50 acres or more

• No wetlands• No ponds

.. [cls]>=120 AND [cls] <200

.. [gridcode]=4

.. [slope>]=8

… [acres]>=50

… Switch selection… Ditto

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Switch?

Selected unselectedUnselected Selected

Selected = NOT(selected)

Where?

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Plan

TAX

AREA OKCLS OK

Export

attribute

CLS OK AREA OK

BOTH OK

INTERSECT

CLS OK

TAX

BOTH OK

NEW SET attribute

Sel from sel’ed setArea ok

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Summary

• Selection processing can solve a lot of problems in analysis

• Booby traps abound – due on not paying attention

• Choice of – Saving the results of each operation– Or using the “select from selected

set” trick