GIS Components

GIS  Components

         A GIS is composed of hardware, software, data, humans, and a set of organizational protocols. These components must be well integrated for effective use of GIS, and the development and integration of these components is an iterative, ongoing process.

         The selection and purchase of hardware and software is often the easiest and quickest step in the development of a GIS. Data collection and organization, personnel development, and the establishment of protocols for GIS use are often more difficult and time consuming endeavors.

Hardware for GIS

       A fast computer, large data storage capacities, and a high-quality, large display form the hardware foundation of most GIS. A fast computer is required because spatial analyses are often applied over large areas and/or at high spatial resolutions.

       Calculations often have to be repeated over tens of millions of times, corresponding to each space we are analyzing in our geographical analysis. Even simple operations

May take substantial time on general-purpose computers when run over large areas, and complex operations can be unbearably long-running.

     While advances in computing technology during the past decades have substantially reduced the time required for most spatial analyses, computation times are still unacceptably long for a few applications.

     While most computers and other hardware used in GIS are general purpose and adaptable for a wide range of tasks, there are also specialized hardware components that are specifically designed for use with spatial data.

     GIS require large volumes of data that must be entered to define the shape and location of geographic features, such as roads, rivers, and parcels. Specialized equipment, described in Chapters 4 and 5, has been developed to aid in these data entry tasks.

GIS Software

     GIS software provides the tools to manage, analyze, and effectively display and disseminate spatial information GIS by necessity involves the collection and manipulation of coordinates.

    We also must collect qualitative or quantitative information on the no spatial attributes of geographic features. We need tools to view and edit these data, manipulate them to generate and extract the information we require, and produce the materials to communicate the information we have developed.

   GIS software provides the specific tools for some or all of these tasks. There are many public domain and commercially available GIS software packages, and many of these packages originated at academic or government-funded research laboratories.

   The Environmental Systems Research Institute (ESRI) line of products, including ArcGIS, is a good example. Much of the foundation for early ESRI software was developed during the 1960s and 1970s at Harvard University in the Laboratory of Computer Graphics and Spatial Analysis.                 

   Alumni from Harvard carried these concepts with them to Redlands, California, when forming ESRI, and included them in their commercial products.

Open Geospatial Consortium

      We will briefly cover the most common GIS software, but first wish to introduce the Open Geospatial Consortium (OGC). Their efforts have eased sharing across various GIS software and computer operating systems. Standards for data formats, documentation, program interactions, and transmission have been developed and published-

Functions commonly provided by Gis Software 

 (www.openspatial.org), and lists of standards-compliant software compiled. While some data structures remain opaque or proprietary, most have become open, and common standards ease community adoption, reduce barriers to switching among software, or adopting multiple geospatial processing packages.

          Compliance with the standards is a plus from a user’s perspective, so a quick review of the OGC-compliant list is recommended when selecting a software platform. Our software descriptions include the most widely used software packages, but are not all-inclusive. There are many additional software tools and packages available, particularly for specialized tasks or subject areas. 

ArcGIS

        ArcGIS, in its various online, desktop, and server versions, comprises the most popular GIS software suite at the time of this writing. ESRI, the developer of ArcGIS, has a worldwide presence.

     ESRI has been producing GIS software since the early 1980s, and ArcGIS is its most recent and well developed integrated GIS package. In addition to software, ESRI also provides substantial training, support, and fee consultancy services at regional and international offices.

   ArcGIS is designed to provide a large set of geoprocessing procedures, from data entry through analysis to most forms of data output. As such, ArcGIS is a large, complex, sophisticated product. It supports multiple data formats, many data types and structures, and literally thousands of possible operations

that may be applied to spatial data. It is not surprising that substantial training is required to master the full capabilities of ArcGIS.

  ArcGIS provides wide flexibility in how we conceptualize and model geographic features. Geographers and other GIS-related scientists have conceived of many ways to think about, structure, and store information about spatial objects.

  ArcGIS provides for the broadest available selection of these representations. For example, elevation data may be stored in at least four major formats, each with attendant advantages and disadvantages.

  There is equal flexibility in the methods for spatial data processing. This broad array of choices, while responsible for the large investment in time required for mastery of ArcGIS, provides concomitantly substantial analytical power.

                                                                     QGIS

  QGIS is an open-source software project, an initiative under the Open Source Geospatial Foundation. The software is a collaborative effort by a community of developers and users. QGIS is free, stable, changes smoothly through time, with the source code available so that it can be extended as needed for specific tasks.

It provides a graphical user interface, supports a wide variety of data types and formats, and runs on Unix, MacOSX, and Microsoft Windows operating systems. As with most open source software, the original offering had limited capabilities, but with an average of approximately two updates a year since 2002, QGIS provides a large number of basic GIS display and analysis functions.

          An interface has been developed with GRASS, another open-source GIS with complementary analytical functions, but that lacks as straightforward a graphical user interface.

                                                     GeoMedia

      GeoMedia and related products are a popular GIS suite originally developed and supported by Intergraph, Incorporated. Geo- Media offers a complete set of data entry, analysis, and output tools.

     A comprehensive set of editing tools may be purchased, including those for automated data entry and error detection, data development, data fusion, complex analyses, and sophisticated data display and map composition. Scripting languages are available, as are programming tools that allow specific features to be embedded in custom programs, and programinglibraries to allow the modification of GeoMedia algorithms for special-purpose software.

  GeoMedia is particularly adept at integrating data from divergent sources, formats, and platforms. Intergraph appears to have dedicated substantial effort toward the OpenGIS initiative, a set of standards to facilitate cross-platform and cross-software data sharing. Data in any of the common commercial databases may be integrated with spatial data from many formats. Image, coordinate, and text data may be combined.

  GeoMedia also provides a comprehensive set of tools for GIS analyses. Complex spatial analyses may be performed, including queries, for example, to find features in the database that match a set of conditions, and spatial analyses such as proximity or overlap between features. World Wide Web and mobile phone applications are well supported.

MapInfo

       MapInfo is a comprehensive set of GIS products developed by the MapInfo Corporation, but now a part of Pitney Bowes. Map- Info products are used in a broad array of endeavors, although use seems to be concentrated in many business and municipal applications.

    This may be due to the ease with which MapInfo components are incorporated into other applications. Data analysis and display components are supported through a range of higher language functions, allowing them to be easily embedded in other programs                            In addition, MapInfo provides a flexible, stand-alone GIS product that may be used to solve many spatial analysis problems. Specific products have been designed for the integration of mapping into various classes of applications. For example, Map-Info products have been developed for embedding maps and spatial data into wireless handheld devices such as telephones, data loggers, or other portable devices.

     Products have been developed to support internet mapping applications, and serve spatial data in World Wide Web-based environments. Extensions to specific database products such as Oracle are provided.

Idrisi

    Idrisi is a GIS system developed by the Graduate School of Geography of Clark University, in Massachusetts. Idrisi differs from the previously discussed GIS software packages in that it provides both image processing and GIS functions. Image data are useful as a source of information in GIS.

   There are many specialized software packages designed specifically to focus on image data collection, manipulation, and output. Idrisi offers much of this functionality while also providing a large suite of spatial data analysis and display functions.

   Idrisi has been developed and maintained at an educational and research institution, and was initially used primarily as a teaching and research tool. Idrisi has adopted a number of very simple data structures, a characteristic that makes the software easy to modify. Some of these structures, while slow and more space demanding are easy to understand and manipulate for the beginning programmer.

   The space and speed limitation have become less relevant with improved computers. File formats are well documented and data easy to access. The developers of Idrisi have expressly encouraged researchers, students, and users to create new functions for Idrisi.

   The Idrisi project has then incorporated user developed enhancements into the software package. Idrisi is an ideal package for teaching students both to use GIS and to develop their own spatial analysis functions.

   Idrisi is relatively low cost, perhaps because of its affiliation with an academic institution, and is therefore widely used in education. Low costs are an important factor in many developing countries, where Idrisi has also been widely adopted.

Manifold

         Manifold is a relatively inexpensive GIS package with a surprising number of capabilities. Manifold combines GIS and some remote sensing capabilities. Basic spatial data entry and editing support are provided, as well as projections, basic vector and raster analysis, image display and editing, and output.

       The program is extensible through a series of software modules. Modules are available for surface analysis, business applications, Internet map development and serving, database support, and advanced analyses.

       Manifold GIS differs from other packages in providing sophisticated image editing capabilities in a spatially referenced framework. Portions of images and maps may be cut and pasted into other maps while maintaining proper geographic alignment. Transparency, color-based selection, and other capabilities common to image editing programs are included in Manifold GIS.

                                              GIS in Organizations

   Although new users often focus on GIS hardware and software components, we must recognize that GIS exist in an institutional context. Effective use of GIS requires an organization to support various GIS activities.

   Most GIS also require trained people to use them, and a set of protocols guiding how  the GIS will be used. The institutional context determines what spatial data are important, how these data will be collected and used, and ensures that the results of GIS analyses are properly interpreted and applied. GIS share a common characteristic of many powerful technologies.

    If not properly used, the technology may lead to a significant waste of resources, and may do more harm than good. The proper institutional resources are required for GIS to provide all its potential benefits. GIS are often employed as decision support tools (Figure 1-20).

   Data are collected, entered, and organized into a spatial database, and analyses performed to help make specific decisions.

   The results of spatial analyses in a GIS often uncover the need for more data, and there are often several iterations through the collection, organization, analysis, output, and assessment steps before a final decision is reached.

    It is important to recognize the organizational structure within which the GIS will operate, and how GIS will be integrated into the decision-making processes of the organization. One first question is, “What problem(s) are we to solve with the GIS?” GIS add significant analytical power through the ability to measure distances and areas, identify vicinity, analyze networks, and through the overlay and combination of different infor-

 

mation. Unfortunately, spatial data development is often expensive, and effective GIS use requires specialized knowledge or training, so there is often considerable expense in constructing and operating a GIS. Before spending this time and money there must be a clear identification of the new questions that may be answered, or the process, product, or service that will be improved, made more efficient, or less expensive through the use of GIS. Once the ends are identified, an organization may determine the level of investment in GIS that is warranted. Incorporated in the question–collect–analyze– decide loop when solving problems.