What is GIS?
Loclyn Anderson GIS Coordinator City of Tallahassee, Utility Support Services GIS 2602 Jackson Bluff Road,Tallahassee, FL 32304 Mark Haro GPS Specialist City of Tallahassee, Utility Support Services GIS 2602 Jackson Bluff Road, Tallahassee, FL 32304 Abstract A growing number of utility personnel are being exposed to information technology (IT). It has become important to communicate the basic concepts of GIS, coupled with it’s applications as related to AM/FM projects. This paper will explain the fundamental concepts, terms and planning requirements for a Geographic Information System (GIS). Understanding the differences between computer aided design (CAD), geographic information system (GIS) and automated mappinglfacilities management (AM/FM) technologies can provide a solid foundation for utility IT projects. This will result in utility personnel being more adept at comprehending and utilizing diverse information. What is GIS “Geographic Information Systems (GIS) are computer based systems that are used to store, retrieve and manipulate geographic data”. As a definition, this statement is acceptable and true. To the novice, the statement can prove more confising. As more industries are exposed to these types of systems, it is important to understand completely what is GIS. The best way to begin is to first learn GIS terminology. Secondly, we must gain an understanding of the functions and concepts of a GIS. Thirdly we must learn how to acquire planning information to implement GIS. GIS is a term often used in the technical work force. Oi%n we will not admit to our lack of understanding or knowledge about such a “hot” topic. The first step in better comprehending the ideas of GIS is to become familiar with GIS terminology. Words like “accuracy, feature, rubbersheeting, node, geocode, and COGO” are often terms we hear but do not always understand. In the attached glossary of terms, you will find the definitions of words often used by the GIS community. Space is also available to add words of your own. Study these terms in order to be more conversant on matters of GIS as well as grasp abetter understanding of GIS concepts. The second step is to learn and gain an understanding of the fimctions and concepts of a GIS. This can seem like the most diflicult part of the learning process, but in reality is very simple. A GIS has four(4) major components: data entry, data management, data manipulation and analysis and finally, data output. Let’s explore each area more closely. Data Entrv or Data Inrmt: This component is often referred to as the data conversion or data collection stage. Normally, data exists on paper maps or hand drawn maps, electronic maps such as AutoCad maps, aerial photographs, or even satellite images. You may have data that has not been captured yet, or data that has been stored only in the minds of veteran employees. In order to have a successful GIS we must first put all data into one system. In most cases, this would require some sort of conversion, or merging all data into one system. Geographic accuracy may or may not be an issue. GIS, however, is a tool that can assist in locating and mapping facilities with a higher level of accuracy, thus providing integrity to your data. Data entry or conversion can be the most costly part of your GIS project. It could take months or even years to initially collect and convert data. This is when you must decide what your accuracy requirements will be. After this decision is made, standards must be set and followed. Once data is entered or converted with inaccuracies, datawill output inaccuracies. Data collection may be performed by field crews gathering data manually. GPS is a tool often used by companies to capture accurate data along with information about the location or facility. This is called attribute data or feature data. Attribute data is stored in the database and is related geographically to a point or feature on the earth’s surface. By using a tool like GPS, capturing accurate data is an tiordable possibility and is an easy way to update data. Data Manamnent: Data management is the process of storing and retrieving data from a data base. Once data is captured or converted it must be managed and maintained. Updates and changes must be made on a regular basis in order to ensure data integrity. Standards must also be in place so data is always up-to-date. A GIS is more usefil if current data is available for analysis. Planning the structure of the database is critical because it will determine the ease and speed of data retrieval. Good data is the key to a solid and successful GIS. Data is often forgotten after the initial conversion or collection. When this happens, it slows or halts GIS projects because users want current data for analysis. Therefore, once data is captured, converted or entered, it must be maintained and managed. Users who are responsible for updating and maintaining data should be identified early in the project to avoid data disasters. Data Manitmlation and Ana.hsis: Specific GIS applications are the most common way to manipulate and analyze geographic data. Simple database queries are also ways to obtain information stored in a GIS. This component concentrates on what you want from the data. Data can be manipulated in many ways. It is in this stage that the people using the data dictate what they want from the data and then applications are written to perform those functions. Applications can include standard queries, map generation and production, marketing analysis, reports, data entry forms, work order tracking, trouble call routing, and dispatching. The applications are limited only by project budgetary constraints and time. Data OutPut: Data output is best defined as data in the form of maps, tables, or text in both hard copy (paper copies) or sofl copy (electronic files). This component is what most users want first. Understanding that the data collection and conversion is first will help produce better quality output. Visuals are important tools in business. A GIS can produce great visuals if the data is accurate and well maintained. Remember, without data, a GIS can not exist. How do I plan for a GIS? How do I implement a GIS? These questions are often asked to late in the process. In order to successfully implement a GIS, you must first spend time planning for what you want your GIS to do. GIS can perform many functions. It can house a landbase, infrastructure, facilities, utility lines, and countless other layers of data. These systems can be polluted with bad data which cause fictional problems with hardware and sof~are. Planning in advance can prevent many of the problems associated with a GIS. The first step is to write a project plan. Project Work Plans (PWP) are used to ascertain your hardware, datq training and staff support needs and to ensure that the appropriate resources are available. The purpose of a PWP is to outline the scope of work related to a project. It is the major planning and communication tool within the GIS section as well as between the GIS Section, Division Heads and the user community at large. The PWP is drailed before a new project is begun. It should then be discussed with the Division heads, who will route it to the appropriate GIS staH. As work on the project proceeds, the PWP may be modified to reflect changes in scope, timetable, or deliverables. Each modification should be dated, discussed and re-routed. Each PWP should include the following areas: Overview: This is a brief overview of the intended project. Proiect Descri~tion: A brief description of the project. Purpose: Why the project is needed, and why GIS has been determined to be the appropriate tool. Proiect Goals and Objective Time Line: An outline of goals and objectives listed with a realistic time line. Promess to Date: Objectives which have been successfully completed. This is to be updated as the project progresses. Proiect Sume: Gqgraphic region covered by the project, data sets to be used or analyzed, other software to be integrated, etc. Proiect Objectives: Usually a detailed list of questions to be answered, or action steps to be accomplished. Proiect Deliverables: The results (maps, databases, files, processes, applications) of the project. StafT Requirements and Responsibilities: Include GIS staff, division, and other staff necessary to make project successful. Include list of responsibilities of each staff. Once the areas of the project work plan have been defined and documented, then soliciting for support is easy. Each project must have management support. If management is supportive, then budgeting is less worrisome. Experience proves, when documentation and research back an ide~ the idea is usually more solid and wins approval. This plan has helped in many cases to assist new and non GIS staff get started and provide valuable guidelines, in addition to winning management support. It is important and encouraged, that this plan be compiled by the entire GIS team. This allows for a smoother implementation and creates team work early in the project. The next step - “How do I implement a GIS? When you have pwpedy and realistically planned for a GIS project, implementation is much easier. All the data conversion, collection or input issues have already been thought through and documented. Ideas, goals and deliverables have been established and defined. Division heads and managers have been interviewed and have voiced needs. When management support and a budget has been cent%-med, implementation can begin. There are many other areas to learn about GIS and we only chose a few basics to discuss in this paper. Attached is a list of recommended readings for additional information and knowledge for novice GIS users and stafl’. Remember, data is the key to a successful GIS. GIS Terminology accuracv - The degree of correctness of a measurement, or degree of conformity with a standard. Accuracy relates to the quality of a result, and is distinguished from precision, which relates to the quality of the operation by which the result is obtained. accuracy standards - Specific standards to which a finished product must adhere. arc- Location data representing linear features or the borders of polygon features. area - A two-dimensional defined space expressed as a spatial measurement. attribute - Descriptive characteristic of a feature. asimuth - Horizontal direction of a line measured clockwise from a reference plane, usually the meridian. base data - Basic level of map data. Other data is placed on top of base data for comparison or geographic correlation. Most often referred to a base map. base line - Starting point to which fiture changes will be compared. benchmark - Series of tests for hardware and software needs assessment. centroid - an average point in the polygon representing all points in the area. comtmter aided deshm and drafthu (CADD] - Engineering and Architectural design and draf%ng sofbvare. commter aided reaming (CA Ml - Standard mapping operations software. contour - An imaginary line depicting elevation on a map. coordinate - Any of a set of numbers that gives the location of a given point. Coordinate geometry (COGO] - A data entry method that accepts data in the form of survey data (bearings and distances), and calculates coordinates for points. database - A collection of data arranged for ease of retrieval. database mana~ement system (DBMS) - soflware designed to manage a database. data capture - Method used for converting raw or paper data into a computer system. data dictionary - Describes and outlines the contents of a database. ditital data - Tabular or locational information converted to digital form for use with computers. digitizing - The process of converting paper maps into a digital format for use with computers. edge matching - The process of identifying a common point where a line or symbol crosses a shared border of two adjacent maps. feature - Basic geographic elements used to represent physical and cultural features on the earth represented by points, lines and polygons. geocoding - Assigning locational coordinates to map features based on an earth based coordinate system. grid - A pattern of lines forming squares used as a reference for locating points on a map. layers- ovel-laYs of data that de~ with one theme. LaYers should have the s~e ~ordinate system. line - One-dimensional object having a length and direction which connects to at least two (2) points. map projection - Systematic drawing of lines of a plane surface to represent the parallels of latitude and the meridians of longitude of the earth. node - A common point between two (2) or more line segments. point- Map symbol that refers to an object that has no dimension. polygon- Atwo-dimensional fiiwwiththree (3 ormore=Cs whichintersect atPoin~ or nodes forming an area. raster - Computer assisted cartography created by a pattern of dots that give the appearance of a somewhat abstract map. rubbersheeting - Process of stretching and shrinking an area or portion of a map or image to fit within selected control points. scale - Ratio of the distance between two points on a map and the earth distance between the same two points. source material or data - Any type of data required for implementation of a GIS. (Examples include: aerial photos, maps (paper and digital), charts, sketches, written reports, etc.) smtial data - Data applying the location of geographical entities with their spatial dimensions which are points, lines, area or surface. topography - The configuration of the surface of the earth. topology - Refers to the spatial relationships between the points and lines that define geographic features. vector - One dimensional data comprised of coordinate representations of locations on the earth as points, lines, and polygons. Acronyms and Abbreviations AM/FM - Automated Mapping/Facilities Management ASPRS - American Society for Photogrammetry and Remote Sensing CADD - Computer aided drafting and design CD-ROM - Compact-disk read only memory COGO - Coordinate geometry DBMS - Database management system DEM - Digital elevation model DLG - Digital line graph DTM - Digital terrain model EDM - Electronic data management FGCC - Federal Geodetic Control Committee GIS - Geographic Information System GPS - Global Positioning Systems IGES - Initial graphics exchanges standards LRIS - Land related information system NAD 83- North American Datum of 1983 NIWAS - National Map Accuracy Standards PPs - Precise positioning services SIF - Standard information format SPOT - Satellite Probatoire pour l’Observation de la Terre TIFF - Tag image file format TIGER - Topologhxdly integrated geographic encoding and referencing system TIN - Triangulated irregular network URISA - Urban and Regional Information Systems Association USGS - United States Geological Survey UTM - Universal Transverse Mercator WGS 84- World Geodetic System 1984 Suggested Readings for Introduction to GIS GIS BOOK -by Geroge B. Korte, P.E. Geographic Information System by Tor Bernhardsen Geographic Information Systems Information Svstems An Introduction by Jeffery Star and John Estes GIS Data Conversion Handbook by Glenn E. Mongomery and Harold C. Schuch | ||
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