The concept of information is indeed the heart of the rapidly growing field of Geographic Information Systems or GIS. As the world moves into the Information Age, meaningful data and information are becoming the major "currency". With the continuous advances in computer technology, it is easy to concentrate on dazzling computer systems and software, but the real value of any product is the data and the information such data provides. At the heart of any GIS is information.
Chapter 1 introduces the reader to some of the very basic principles of Geographic Information Systems, and also introduces the reader to the ArcView GIS software product from Environmental Systems Research Institute (ESRI). The ArcView software will be used throughout the Training Manual to illustrate the GIS concepts presented in each chapter.
In 1990, the President of the Association of American Geographers, Saul Cohen, was quoted: "Times are changing, and our methods of meeting the needs of the times are also changing. The world is entering the "post-industrial Information Age" a time when information is becoming a major product of, and foundation for, progress. Increasing emphasis on data management is apparent and necessary. Today's focus in geography (or any other discipline) on data handling and data manipulation reflects the national ( and international) emphasis on meeting the needs of the postindustrial information age".
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Spatial data (location data) is at the heart of every GIS application. Spatial data stores the geographic location of particular features, along with information describing what these features represent. The location is usually specified according to some geographic referencing system (e.g., latitude, longitude) or simply by a street address. Spatial data may define some physical characteristic such as location or position, or it may also define a property such as the area of a forest, which is based from defining the position of the forest boundaries.
In Chapter 2, the reader will be introduced to the format and structure of the GIS vector and raster data models. Attribute data in the form of flat files will be explained along with the topological concepts associated with the vector data model. The reader will also be given the opportunity to begin working in the ArcView GIS software environment and conduct an exercise focused on using and editing text-based attribute tables.
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Mapping is the process in which we transform features located on the curved three-dimensional surface of the earth onto a flat map sheet. During this transformation process onto the map surface, the earth's properties of shape, area, distance or direction becomes distorted.
In Chapter 3, the reader will learn about the methods used by cartographers in the map making process to reduce the distortion caused during this transformation. In addition, the reader will learn about the shape of the earth, datum's, coordinates systems, meridians and parallels, map scale and projection.
The exercises included in Chapter 3 provide the reader with the opportunity to change the map projection and coordinate system geometry of the State of Michigan in order to measure and gain a practical understanding of the distortions which occur during the transformation process.
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GIS is not a computer system for making maps or digital graphics, but rather, a GIS is a set of tools for identifying "spatial" relationships between Geographic features. Therefore, data structure is one of the major decisions initially made in the GIS mapping process. Most GISs are either raster-based or vector-based, but many employ both formats.
A GIS map represents a set of real-world objects in a combination of various themes or layers; each presented as map features. Due to this layering, many themes can be displayed for the same geographic area, in a single view.
Spatial data are stored in a computer along with their characteristics, called attribute data. These data are stored in the form of attribute tables. An attribute can be a non-spatial aspect of spatial data, such as name, classification, or color. Attributes come in many forms, including text descriptions, numbers indicating quantities of some sort, and abbreviations or codes.
Selected layers from a GIS database are combined to create a map, known as a composition. In a composition, the choice of layers or themes depends on the needs of the user and on the existing data in the GIS. Compositions may be viewed and stored in a computer, or printed out as maps.
In Chapter 4, we examine spatial data and their characteristics, how to transfer hard copy or map data into the digital environment through the process of digitizing and geocoding,data editing and transformation and the table functions of joins and links. Following these topics, the reader will conduct several exercises focused on conducting table queries, summarizing tables, joining and linking tables and an exercise in creating data through the process of on-screen digitizing.
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GIS professionals are involved in the use and application of GIS in a wide range of areas, including government, business, and planning. As noted in an earlier chapter, a GIS consists of the computer software, hardware, and peripherals that visualize, manage, manipulate, and analyze geographically referenced data. A GIS can analyze spatial interactions between static and dynamic entities in the environment. Technically, three unique, but interrelated strengths, characterize a GIS.
1. Spatial data management.
2. Interactive visualization.
3. Spatial analysis and decision-making support.
You have been exposed to the first two strengths in the previous chapters. In this chapter, we discuss how GIS can be the foundation for machine-assisted problem solving that is, performing spatial analysis using spatial joins in ArcView GIS.
In the Chapter 5 exercises, you will identify spatial features through the use of spatial analysis. First you will identify Public Act 307 (hazardous pollution) sites which are in the proximity of drinking water sources in the Detroit area. Next, you will determine which highways are included in certain towns and finally, you will be able to determine schools that are located in various cities.
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- Who is your audience?
- What message are you giving?
- Why are you presenting this information?
- How will this message be presented?
The process of map production requires a great deal of thought. The main goal is to provide a user-friendly tool that will inform the user.
The basic elements of a map are Title, Scale, Projection, Symbols, Legend, North Arrow, Notes and Layout. The Title should address the major theme of your map presentation. A map's Scale and Projection will be defined by its intended purpose. For example to show small areas in great detail or large areas in little detail. Another important element is your choice of map symbols. Map symbols serve as a means to identify and describe features, their locations and to visually display them. Symbol use is crucial in conveying information in a clear and meaningful manner. The map symbols and their associated colors, are also used in the Legend to help the user easily identify important features. The North Arrow is used to help the user orient the map. Notes are textual information and used to describe the source of the data presented on the map, and notify the user of the maps intended use.
In the exercises in this chapter, you will use Arc View GIS to construct a Layout for your GIS map and print a hard copy map.
(C) Copyright by IGRE ,Eastern Michigan University, Ypsilanti, MI, 48197, USA
This page was updated on April 4th, 2005.