Regions in ArcINFO

Regions can handle overlapping, noncontiguous and nested areas and makes real-world features easier to represent and analyze.

Data management is more efficient, as each region only requires one attribute record.

Overlapping ranges Non-contiguous areas

Overlapping polygons - ranges for multiple wildlife species - fires (burned areas) through time, fire atlas data - countries of the world through time - managing habitats, that are not spatially exclusive - managing different floor plans for a building

Non-planar features - data in different ‘planes’, for example, soil data collected at various soils depths - geological data that overlaps at various depth levels

Noncontiguous areas - islands that comprise the state of Hawaii as a single feature

Regions in ArcINFO

Regions can have VOID AREAS

Regions may have multiple sub-classes

- A regions coverage may contain one or more region subclasses - A subclass contains one or more region features - Each region subclass can be visualized as lying in its own ‘plane’ above the polygon topology. - Each region subclass has its own set of attributes because each subclass has its own PAT.

POLYGONS

- cannot overlap - single contiguous area - feature class partitions space - cannot be nested - one feature class per cover

REGIONS - can overlap- multiple noncontiguous areas- void areas allowed- can have nested features- many feature classes per cover

Creating Regions ?

- Regions can be created from coordinate files or digitizing.

- Regions can be created and edited interactively using ARCEDIT.

- Regions can be generated directly from existing coverages using points or nodes, arcs, polygons or existing regions.

- Regions can be created from queries and logical operations on polygon or region coverages

REGIONPOLY – converting regions to polygon coverages

POLYREGION – creating regions from polygons

… in ArcINFO

Region commands in ArcInfo, ArcPlot and ArcEdit

………. a few region commands

regionpolylist creates an INFO file that lists the polygons that belong to each region in the specified subclasses

regionpolycount counts the total number of regions, and regions by subclass, for each polygon. The selected polygon belongs to two regions, one from each subclass

regionxarea creates an output INFO file to describe the overlap relationship between the two regions in area and percent

regionselect selects a set for polygons or regions through Boolean selection of attribute values of polygons or regions from multiple subclasses

regionquery creates new regions based on the attribute values of input region or polygon layers and aggregates regions according to specified attribute items.

Example of fire-atlas data from the Selway – Bitterroot Wilderness

• Western redcedar• Douglas-fir• Grand Fir• Lower Subalpine Dry• Lower Subalpine Moist• Upper Subalpine Dry• Upper Subalpine Moist• Rock/Alpine/Barren Land

Potential Vegetation Types

Fire Eras

Modern Suppression 1935 - 1974

Wildland Fire Use 1975 - 1996

Pre-Modern Suppression Prior to 1935

Changes within the fire eras

• Fire frequency• Severity

Fire Regime“The nature of fires occurring over an extended period of time”

-(Brown, 1995)

NaExtremely infrequentVery infrequentInfrequentFrequentVery frequent

Fire frequency

Historic Fire Regimes1900, ICRB

Current Fire Regimes1995, ICRB

Fire regimes have been described with the help of Digital Fire Atlases and Aerial Photo Interpretation

Stand Replacing Non-Lethal Mixed Unknown

Results – Fire Severity ….by Casey Teske

Ar e

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Create a map showing how many times each polygon in the Selway-Bitterroot regions coverage has burned between 1880 and 1996. Hint: use the REGIONPOLYCOUNT command

What is the average area burned per year within the three ‘fire eras’:- Pre-modern suppression 1880 - 1934

- Modern suppression 1935 - 1974 - Wildland fire use 1975 - 1996

……examples of how to use regions

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