Using GIS for Analysis:

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Using GIS for Analysis
A sample of approaches

• Queries
• Re-classification
• Map overlay

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Queries

• Spatial
• Questions about location, size, shape, distances,
  etc.
• Where is ___ ?
• Which is the longest US route within the county?
• Which is the most isolated golf course?
• Require a map or GIS

• Aspatial
• Questions about attributes
• How many ___ are there?
• Which is the oldest?
• Which has the greatest land value?
• Could be answered with database software alone

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Combination Queries

• Some queries involve 2 or more criteria (spatial
  or aspatial)
• For these, use Boolean operators AND, OR, NOT

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Combination Queries

• Which golf courses are in Mesa AND have 36 holes?

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Combination Queries

• Which golf courses are in Mesa OR have 36 holes?

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Combination Queries

• Which 36-hole golf courses are NOT in Mesa?

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Using GIS for Analysis

• Queries
• Re-classification
• Map overlay

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Reclassification

• Result of query is a new data layer

Which land in Maricopa County is federally
managed?
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• Query approach
• Which land is managed by BIA OR BLM OR BOR OR FS
  OR FWS OR NPS?

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Reclassification Approacha New Data Layer
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Reclassification approach
Data Table Before Reclassification
cell Ownership
A1 BLM
A2 BLM
A3 FS
A4 Non-fed
Data Table After Reclassification
Cell Ownership
A1 Fed
A2 Fed
A3 Fed
A4 Non-fed
Reclassification is often a step to get data
ready for overlay analysis
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Using GIS for Analysis

• Queries
• Re-classification
• Map overlay

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Map Overlay

• Ian McHarg (Design with Nature) pre-computer
  advocate of map overlay

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Map Overlay vs. Combination Query

• Which Golf Courses are in Mesa AND have 36
  holes?

Map overlay produces a new data layer
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Map Overlay vs. Reclassification

• Which land in Maricopa County is Federally
  managed?

Map overlay involves data from two or more layers
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An example of a GIS analysis
GIS as a tool in fire managementSequoia-Kings
Canyon National Park
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GIS as a tool in fire managementSequoia-Kings
Canyon National Park

• Question
• Where should we do controlled burns, in order to
  best reduce the risk of severe out-of-control
  wildfires?

• Several aspects to consider
• Ecological need (natural fire interval)
• Human value Infrastructure, human life safety
• Hazard ability to control a fire, once started
• Risk based on historic record of wildfire
  occurrence

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Analysis to determineecological need

• Data available

Maximum average interval for fire occurrence
1. Natural Occurrence of fire, by species,based
on analysis of tree rings
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Analysis to determineecological need

• Data available

2. Vegetation map
Ponderosa forest
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Analysis to determineecological need

• Data available

3. Historical fires
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Analysis to determineecological need

• Analysis steps

Date of last fire
Vegetation types
Reclassify
Reclassify
Fire return interval
Years since last fire
FRI
TSLF
Overlay
Departure from natural fire interval
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Analysis to determineecological need

• Analysis steps

Departure from natural fire interval
Reclassify
Departure index Need to burn
lt-5 Extreme
-5 to -2 High
-2 to 0 Moderate
gt 0 Low
Ecological need for burn
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Map of ecological burn need

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Additional steps .
Vegetation types
Date of last fire
slope
Types of fuel
elevation
Ecological burn need
Ability to control burn
Where to do controlled burns
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Additional steps .
Vegetation types
Date of last fire
slope
Types of fuel
elevation
Ecological burn need
Ability to control burn
Infrastructure Safety issues
Risk of wildfire
Where to do controlled burns
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Todays Challenges

• Environmental, Social, Political, Economic
• Local, National, Global
• Information is an essential tool to address these
  issues
• Geographic technology can help to answer more
  complex questions covering larger geographic
  extents than ever before

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Geographic information

• Involves a specification of location on the
  earths surface (WHERE)
• Also involves WHAT is at that location
• Goal is to uncover WHY something is located where
  it is