GIS and Landscapes

Lisa A. SchulteForest Ecology and Management

Topography

Soils

Climate

VegetationDistribution

y

x1

x2

x3

= f(c, s, t)

ModelProbability of

What are geographical/spatial data?

What are geographical/spatial data?

Any data that can be mapped

Have x- and y-coordinate

Types of spatial data?

Types of spatial data?

Topographic maps

Hydrographic maps

Political/Administrative/Property boundaries

Road networks

Remote Sensing (aerial photography, satellite)

Data on people: census data, land use, marketing

surveys

Data on natural resources: climate, geology,

hydrology, soil, natural hazards, biological activity

Data on utilities

Why use GIS?

Limitations of a map:

2-D representation of 3-D

Limited to a single scale

Snapshot in time

Difficult to manipulate data

GIS OvercomesThese!!!

What is a GIS?

A set of computer tools for collecting, storing,

retrieving, transforming, and displaying spatial data

from the real world (Burrough and McDonnell 1998).

Many functions = may parts.

Computer

Screen

Printer

Scanner

DigitizingTable CD

FTP

CD

Network

Core parts of a GIS:

1) User interface/GIS tools• Responsible for capturing, storing, retrieving,

displaying, customizing, and sharing data

2) Spatial Database• Responsible for storing and querying data

Computer

Screen

Printer

Scanner

DigitizingTable CD

FTP

CD

Network

SpatialDatabase

How do we represent the real world digitally?

Physicalreality

Real worldmodel

Datamodel

Database

Maps/reports

From: Bernhardsen 1999

Actual phenomena:-Properties-Connections

Entity:-Type-Attributes-Relationships

Object:-Type-Attributes-Relationships-Geometry-Quality

Object:-Type-Attributes-Relationships-Geometry-Quality

Spatial Data Components

Spatial Data

AttributeComponent

Geometric Component

Categorical

PointLine

Area (polygon/cell)

Qualitative Quantitative

OrdinalIntervalRatio

Spatial Data Components

Spatial Data

AttributeComponent

Geometric Component

Categorical

PointLine

Area (polygon/cell)

Qualitative Quantitative

OrdinalIntervalRatio

Geometric Representation

Point: 0-D object that specifies geometric location specified through a set of coordinates.

Line segment (vector): 1-D object that is a direct line between 2 endpoints.

String: a sequence of line segments.

Polygon: 2-D object bounded by at least 3 1-D line segments.

Raster cell/pixel: 2-D that represents an element of regular tesselation of a surface.

Vector Data Model

Raster Data Model

Raster Data Model

TIN Data Model

TIN Raster Data Model

Vector vs. Raster Very important choice!

Advantages of vector:

• Good representation of entity data models

• Space efficient storage of data

• Topology can be described explicitly and be

easily manipulated

• Efficient query operation

Advantages of raster:

• Simple data structure

• Efficient representation of highly variable data

• Mathematical modeling easier because all

entities have simple, regular shape

Georeferencing:

Matching up spatial database with earth coordinate

system

Coordinate systems

• Latitude/Longitude – distortion near poles

• Universal Transverse Mercator

– divide globe up into strips

– good for large datasets

• State Plane

– each state has own

– most accurate for at this scale

How do we represent the real world digitally?

Selecting applicable scale

Through simplification!

Two basic components associated with spatial data:

1. Geometric component Data Model

2. Attribute component Classification

Who produces spatial data?

Who produces spatial data?

National agencies (USGS, USFS, NOAA, DNR)

Military organizations

Remote sensing companies (aerial photography, satellite)

Utility companies

Climatologists, geologists, hydrologists, ecologists,

geographers, oceanographers, etc.

Grad students!

Data Acquisition:

Computer

Screen

Printer

Scanner

DigitizingTable CD

FTP

CD

Network

Data Acquisition:

Field surveys

Digitizing

• Trace lines on map

• Labor intensive

Scanning

• Scan map

• Edit data

Remote sensing

Deriving from existing GIS data layers

Downloading

Web Sources of GIS Data:

USGS

• Remotely sensed, DEMs, Soils, Hydrographies

• http://www.usgs.gov

NOAA - National Climatic Data Center

• Climate

• http://www.ncdc.noaa.gov/ol/about/ncdcnoaa.html

US Census Bureau

• Demographic

• http://www.census.gov/geo/tigerline/tl_1998.html

Wisconsin State Cartographer’s Office – Wisconsin Land

Information Clearinghouse

• Various

• http://wisclinc.state.wi.us/

GIS software:

Computer

Screen

Printer

Scanner

DigitizingTable CD

FTP

CD

Network

GIS software:

Arc/Info

• ESRI (http://www.esri.com/)

ArcView

• ESRI (http://www.esri.com/)

IDRISI

• Clark Labs (http://www.clarklabs.org/)

GRASS

• Baylor University (http://www.baylor.edu/~grass/)

Imagine

• ERDAS (http://www.erdas.com/products/product.html)

GIS functionality

Spatial queries

• Site analysis

• Trend analysis

• Pattern analysis

Spatial overlay

Spatial modeling

Network operations

Interpolation

Digital terrain analysis

Statistical analysis

Who uses spatial data?

Who uses spatial data?

Agriculture

Archaeology

Demographers

Environmental scientists and managers

Epidemiology and health scientists

Emergency services

Land planners

Marketing agencies

Naviation

Real estate

Tourism

Utilities

Uncertainty…

From: Lunetta et al. 1991

Spatial data in landscape ecology…

From: Bernhardsen 1999

Resolution?Data model?Attribute representation?Trustworthiness?

Nine factors to consider when embarking on spatial analysis with GIS:

1. Real world phenomena simple/complex?

2. Data used to describe real world phenomena detailed/generalized?

3. What data types are used to describe the phenomena?

4. Can phenomena be represented in a database exactly/vaguely?

5. Do database entities represent discrete/continuous real world entities?

6. Were the attributes of database entities obtained by complete

enumeration or by sampling?

7. Will the database be used for descriptive/administrative/analytical

purposes?

8. Will the database be used to make inferences about the real world?

9. Is the process under consideration static/dynamic?

(Burroughs and MacDonnell 1998)

References

Bernhardtsen, T. 1999. Geographic information systems: an introduction, 2nd edition. John Wiley and Sons, New York, New York, USA.

Burrough, P. A., and R. A. McDonnell. 1998. Principles of geographic information systems. Oxford University Press, Inc., New York, New York, USA.

Johnston, C.A. 1998. Geographic information systems in ecology. Blackwell Science, Oxford, UK.

Lunetta, R.S., R.G. Congalton, L.K. Fenstermaker, J.R. Jensen, K.C. McGwire, and L.R. Tinney. 1991. Remote sensing and geographic information system data integration: error sources and research issues. Photogrammetric Engineering and Remote Sensing 57:677-687.