Landscape Ecology - Lecture Notes

Geographic Information Systems (GIS)

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1. What Is GIS?

• Geographic information systems (GIS) are a group of computerized tools for collecting, storing, retrieving, transforming, and displaying spatial data from the real world for a particular set of purposes (Burrough, 1986).

• In other words, they are integrated database management and analysis systems that are capable of the input, storage, and numerical manipulations of geographic or spatially referenced data.

• The development of geographic information systems may date back to as early as the 1960s.

• Geographic information systems have been developed by linking parallel developments in several separate spatial data processing disciplines, including digital cartography, satellite-based surveying, photogrammetry, remote sensing, interactive computer graphics, and spatial modeling.

• GIS's have evolved under the pressure of explosive increase in spatial information and in the great needs for powerful tools to take advantage of our current knowledge base.

• What is GIS? [Video]
  

Development of Geographic Information Systems. Geographic Information Systems have evolved from integrating parallel advances in several spatial data processing disciplines (adapted from Burrough, 1986).

2. What Is a GIS Composed of?

Major Components and Functions of Geographic Information Systems

• A functional GIS consists of both computer hardware and software that enables such operations as information input, storage and manipulations on data layers obtained from such sources as thematic maps, aerial photos, and satellite images.

• The major hardware components of a GIS include a computer (central) processing unit (CPU), a visual display unit (VDU), and peripherals such as digitizers, plotters, printers (Burrough, 1986). In general, five major components of GIS software may be identified as follows:

 

3. How Does GIS Work?

Two Major Approaches in GIS: Vector vs Raster GISs

From a technological perspective, GIS's have developed following two main approaches characterized by the ways in which spatially referenced data are represented and analyzed.

(1) Vector-based GIS:

• Representing spatial data using patterns of points, lines and areas. In other words, all points, lines and polygons are defined in terms of the map variables in a vector structure.

• Advantages of vector methods are: compact data structure, accurate graphics, good representation of phenomenological data structure, complete description of topology with network linkages, and flexibility in retrieval, updating and generalization of graphics and attributes.

• Disadvantages include: complexity in data structure, difficulty for simulation due to the difference in topological form for each unit, and high-priced hardware and software.


(2) Raster-based GIS:

• Raster-based systems store geographic information as points in a regular network of grid cells (pixels or picture elements), whereas the smallest space unit in a raster structure is the grid cell which is equivalent to a point in vector systems. In raster systems, the attributes of features are normally stored directly within the raster grid.

• Advantages include: simplicity in data structure, easiness as to spatial analysis, simulation and combination with remote sensing data, and inexpensive technology.

• Disadvantages are: inefficient use of memory space for graphic data, loss of information with use of large cells, inaccuracy in map representation, and difficulty in network linkages.

• How Does GIS Work?

5. Applications of Geographical Information Systems in Ecological and Environmental Studies

• GIS can facilitate and improve landscape ecological studies in a number of ways, including:

• Aggregate dispersed data ( both maps and paper records) into one setting for better access;
• Effectively link maps (spatial data) with records (attribute data), thereby augmenting the integrity of various data;
• Enable updates of both spatial and attribute information regularly and timely;
• Facilitate spatial modeling of landscape dynamics
  
• Facilitate planning and management actions with improved data quality, rapid data access, and analytical capabilities.
  

6. Major GIS Software Packages

• ESRI (Environmental Systems Research Institute)
• Founded in 1969
• A software development and services company providing GIS software and geodatabase management applications

• IDRISI – GIS and Image Processing product developed by Clark Labs at Clark University.
  

• GRASS GIS – Originally developed by the U.S. Army Corps of Engineers, open source: a complete GIS

• ERDAS IMAGINE by ERDAS Inc; products include Leica Photogrammetry Suite, ERDAS ER Mapper, and ERDAS ECW JPEG2000 SDK (ECW (file format))are used throughout the entire mapping community (GIS, Remote Sensing, Photogrammetry, and image compression).
  

• ESRI's Intro to GIS in PDF

• GIS at ESRI