Contents 1 What is GIS? 2 How GIS works? 3 GIS in Environmental & Ecological Research [Previous Page]

A geographic information system (GIS) is a computer-based tool for mapping and analyzing things that exist and events that happen on Earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public and private enterprises for explaining events, predicting outcomes, and planning strategies. Map making and geographic analysis are not new, but a GIS performs these tasks better and faster than do the old manual methods. And, before GIS technology, only a few people had the skills necessary to use geographic information to help with decision making and problem solving. A working GIS integrates five key components: hardware, software, data, people, and methods. Maybe you already have a computer, many good ideas, and data from our database, what else do you need? Yes, software! GIS software is available at KU through a KU ESRI site license.

A GIS stores information about the world as a collection of thematic layers that can be linked together by geography. This simple but extremely powerful and versatile concept has proven invaluable for solving many real-world problems from recording details of planning applications to modeling global atmospheric circulation.

Geographic information contains either an explicit geographic reference such as a latitude and longitude or national grid coordinate, or an implicit reference such as an address, postal code, census tract name, forest stand identifier, or road name. An automated process called geocoding is used to create explicit geographic references (multiple locations) from implicit references (descriptions such as addresses). These geographic references allow you to locate features, such as a business or forest stand, and events, such as an earthquake, on the Earth's surface for analysis.

Geographic information systems work with two fundamentally different types of geographic models--the "vector model" and the "raster model."

In the vector model, information about points, lines, and polygons is encoded and stored as a collection of x,y coordinates. The location of a point feature, such as a bore hole, can be described by a single x,y coordinate. Linear features, such as roads and rivers, can be stored as a collection of point coordinates. Polygonal features, such as sales territories and river catchments, can be stored as a closed loop of coordinates. The vector model is extremely useful for describing discrete features, but less useful for describing continuously varying features such as soil type or accessibility costs for hospitals. The raster model has evolved to model such continuous features. A raster image comprises a collection of grid cells rather like a scanned map or picture. Both the vector and raster models for storing geographic data have unique advantages and disadvantages. Modern GISs are able to handle both models.

Raster             Vector             Real world

1 Query and Analysis

Once you have a functioning GIS containing your geographic information, you can begin to ask simple questions such as

Who owns the land parcel on the corner? How far is it between two places? Where is land zoned for industrial use?

And analytical questions such as

Where are all the sites suitable for building new houses? What is the dominant soil type for oak forest? If I build a new highway here, how will traffic be affected?

GIS provides both simple point-and-click query capabilities and sophisticated analysis tools to provide timely information to managers and analysts alike. GIS technology really comes into its own when used to analyze geographic data to look for patterns and trends, and to undertake "what if" scenarios. Modern GISs have many powerful analytical tools, but two are especially important.

Proximity Analysis How many houses lie within 100 m of this water main? What is the total number of customers within 10 km of this store? What proportion of the alfalfa crop is within 500 m of the well?

To answer such questions, GIS technology uses a process called buffering to determine the proximity relationship between features.

3 Overlay Analysis

The integration of different data layers involves a process called overlay. At its simplest, this could be a visual operation, but analytical operations require one or more data layers to be joined physically. This overlay, or spatial join, can integrate data on soils, slope, and vegetation, or land ownership with tax assessment.

4 Visualization

For many types of geographic operation the end result is best visualized as a map or graph. Maps are very efficient at storing and communicating geographic information. While cartographers have created maps for millennia, GIS provides new and exciting tools to extend the art and science of cartography. Map displays can be integrated with reports, three-dimensional views, photographic images, and other output, such as multimedia.

You can use a GIS many ways:

Study and Management of Ecosystems

With a GIS you can analyze entire ecosystems.  The National Biological Services uses GIS to study and manage the Gap Analysis Program. Using the GIS they can visualize the ecosystem as a complete unit and display graphics of sensitive areas.  The Bureau of Land Management uses GIS to manage the ecosystem for the Columbia River Basin. Using the GIS they can assess environmental impact, develop planning strategies, and create maps that show the entire system.

Site Characterization
With a GIS you can organize and refine data to help with site assessments, site inspections, and feasability studies.  Data, such as survey, hydrological, and aerial photos, can be organized and evaluated using the GIS.

Tracking the Effects of Pollutants
	The damaging effects of pollution, such as oil spills, can be assessed using a GIS.  With this information, the GIS can model potential contamination for different locations and help develop risk assessment strategies.

Environmental Planning and Management
Using the analysis capabilities of a GIS you can manage relationships among biological and cultural resources.  The Chambers Group uses a GIS to create and monitor the City of Indio's wildlife within the framework of the City's general plan

Analysis Wildlife Populations
	You can use a GIS to display and analyze field data.  In this example, The Chambers Group uses a GIS and the data collected from a Global Positioning System (GPS) to show the distribution and densities of desert tortoise populations.

Tracking Species Distributions
The University of Wisconsin uses GIS to show the recolonization of the eastern timber wolf and the factors that contribute to its success in reestablishing ranges. This map shows how the wolf has been steadily moving east in its efforts to reestablish habitat.

Monitoring Biodiversity
	The Idaho Gap analysis project uses a GIS to show the distribution and conservation of several components of biodiversity.  The GIS helps researchers identify species that should be present in the State management areas but are not (gaps). These species are used as indicators of overall biodiversity, or the lack of it, for a given area.

And much much more .......

© Copyright 1999 Kansas Biological Survey

Last modified 16 January, 2002.