Using GIS for Analysis:

• Queries

• Re-classification

• Map overlay

Real world

Land use

Elevation

Parcels

Streets

Retail

A sample of approaches:

Queries

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

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

Combination Queries

Some queries involve 2 or more criteria (spatial or aspatial)

For these, use Boolean operators: AND, OR, NOT

Combination Queries Which golf courses are in Mesa AND have 36

holes?

InMesa

36holes

Combination Queries Which golf courses are in Mesa OR have 36

holes?

InMesa

36holes

Combination Queries Which 36-hole golf courses are NOT in Mesa?

InMesa

36holes

Using GIS for Analysis

Queries

Re-classification

Map overlay

Reclassification Result of query is a new data layer

Which land in Maricopa County is federally managed?

BIABLMBORDODFSFWSNPS

Query approach:

Which land is managed by BIA OR BLM OR BOR OR FS OR FWS OR NPS?

BIABLMBORDODFSFWSNPS

Reclassification Approach:a New Data Layer

Federallymanaged

Other

Reclassification approach

cell Ownership

A1 BLM

A2 BLM

A3 FS

A4 Non-fedCell Ownership

A1 Fed

A2 Fed

A3 Fed

A4 Non-fed

Reclassification is often a step to get

data ready for overlay analysis

Data Table Before Reclassification

Data Table After Reclassification

Using GIS for Analysis

Queries

Re-classification

Map overlay

Map Overlay

Ian McHarg (“Design with Nature”) – pre-computer advocate of map overlay

Map Overlay vs. Combination Query“Which Golf Courses are in Mesa AND have 36

holes?”

Map overlay produces a new data layer

Map Overlay vs. ReclassificationWhich land in Maricopa County is Federally

managed?

BIABLMBORDODFSFWSNPS

Map overlay involves data from two or more layers

An example of a GIS analysis…

GIS as a tool in fire management:Sequoia-Kings Canyon National Park                           

GIS as a tool in fire management:Sequoia-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

Analysis to determineecological need

Data available:

Vegetation Classification RImax

1 - Ponderosa Mixed Conifer 6

2 - White Fir Mixed Conifer 16

3 - Red Fir Mixed Conifer 50

4 - Lodgepole Pine Forest 163

5 - Xeric Pine Forest 50

6 - Subalpine Conifer 508

7 - Foothills Hardwood & Grassland 17

8 - Foothills Chaparral 60

Maximum average interval

for fire occurrence

1. Natural Occurrence of fire, by species,based on analysis of tree rings

Analysis to determineecological need

Data available:

Ponderosa forest

2. Vegetation map

Data available:

Analysis to determineecological need

3. Historical fires

Analysis steps:

Departure from natural fire interval

Vegetation types

Reclassify

Overlay

Fire return interval

Date of last fire

Reclassify

Years since last fire

FRI Natural

TSLF - FRI Natural

FRI TSLF

Analysis to determineecological need

Analysis steps:

Departure from natural fire interval FRI Natural

TSLF - FRI Natural

Reclassify

Ecological need for burn

Departure index

Need to burn

<-5 Extreme

-5 to -2 High

-2 to 0 Moderate

> 0 Low

Analysis to determineecological need

Map of ecological burn need

Additional steps ….

Where to do controlled burns

Ecological burn need

Ability to control burn

Vegetation types

Types of fuel

slope elevation Date of last

fire

Where to do controlled burns

Ecological burn need

Ability to control burn

Vegetation types

Types of fuel

slope elevation Date of last

fire

Infrastructure & Safety issues

Risk of wildfire

Additional steps ….

Today’s 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

Geographic information

Involves a specification of location on the earth’s surface (WHERE)

Also involves WHAT is at that location

Goal is to uncover WHY something is located where it is