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April - June 2007
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Producing Quality Information Products

A comprehensive approach to data management

"Garbage in, garbage out"

This axiom is as applicable to GIS as it is to any other information system. With all the capabilities GIS possesses, this fundamental principle is sometimes forgotten. The first consideration when designing and managing a GIS should be that it supply the information products needed for a project or department or, more commonly these days, by an entire organization.

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ArcGIS supplies a comprehensive approach to managing spatial data in a complementary fashion on multiple platforms.

GIS information products aren't limited to printed and online maps. Information products generated by a GIS can be charts, graphs, and reports. Data resulting from GIS analysis is also the input for customer relationship management, enterprise resource planning, and other management software.

Reliably creating quality information products requires good data management. GIS practitioners face some of the same data management issues that administrators of other information systems, who function in an enterprise environment with concurrent data users, must handle. These challenges include maintaining accurate and current data, resolving conflicting versions, eliminating undesirable data redundancy, balancing accessibility with security, and reporting and disseminating information.

Spatial Data Requirements

The size of geospatial datasets, the need to maintain datasets that will be used in different ways by different departments in the organization, and the great variety of data types managed in a GIS are some of the data management issues unique or more pressing for those who manage spatial data.

These challenges have evolved as GIS has become more of a mainstream technology. Five to ten years ago, most GIS practitioners lived in a simpler world that focused on project or department implementations of GIS that were typically carried out on workstations. Now GIS is delivered across organizations and on more platforms. ArcGIS Server and ArcWeb Services, two newer GIS platforms, combine spatial data and services distribution and interact with and complement functionality supplied by the desktop.

A New GIS Platform: Server GIS

ArcGIS Server is an integrated server-based GIS that comes with end user applications and services for spatial data management, visualization, and spatial analysis but can also be used to create custom applications in .NET or Java. ArcGIS Server also provides the foundation for geospatially enabling a service-oriented architecture.

Customizing Data Management

Another product, ArcGIS Engine, was designed for developers. It supplies APIs for COM, .NET, Java, and C++ and high-level visual components for building stand-alone applications and for maintaining data as well as other tasks that can answer the specific requirements of both GIS and non-GIS users.

In an earlier era, the relative scarcity and cost of data were often the biggest problems GIS users faced. Now data is far more plentiful and less expensive. The challenge lies in finding data that best meets user needs. In this context, the best data is accurate, current data delivered in a cost-effective manner that enables collaboration and reuse. In practical terms, this means data management for an organization is closely tied to its workflow.

Customizing Data Management

The need to tailor data management to the workflows and information products needed by users in specific industries has led to the development of data models. Esri, in collaboration with consortiums of users and business partners in dozens of industries, has created specific data templates that simplify the integration of datasets at various geographic levels and promote data sharing.

Framework for Data Management

The geodatabase supplies the data management framework and common storage structure for ArcGIS that can be used on desktops, servers, and mobile devices. Spatial data can be maintained in a geodatabase either as a collection of files in a file system or as a collection of tables within a relational database management system (RDBMS). Geographic features in vector format, attribute tables, satellite and aerial imagery, surface modeling data, terrains, network datasets, survey measurements, and cartographic representations can all be stored, accessed, and processed in a geodatabase.

The geodatabase can also implement complex business logic by modeling spatial relationships between data in topologies, networks, and terrains; perform data validation using subtypes and domains; and handle long transactions through versioning. In addition, data can be checked out, verified in the field, reconciled, and checked back in. The transaction history is recorded and can be reviewed in its historical sequence.

Desktop Tools

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The geodatabase can implement business logic by capturing the spatial relationships between features and performing data validation. In this example, the one-to-many association between utility poles and electric transformers is modeled.

Desktop ArcGIS, through the ArcCatalog, ArcMap, and ArcToolbox applications, supplies tools for creating and maintaining spatial data. Personal, multiuser, and file-based geodatabases are created in ArcCatalog. Metadata or information about data is created semiautomatically and can be enhanced in ArcCatalog. Interactive feature editing, a wide range of cartographic tasks, and digitizing from imagery of existing maps are performed in ArcMap. ArcToolbox, available from both ArcCatalog and ArcMap, supplies hundreds of tools for importing, converting, editing, optimizing, and exporting data. The ArcGIS Data Interoperability extension augments ArcMap's direct read and translation capabilities.

In This Issue

The articles in the Focus section demonstrate how public, academic, and private organizations have met the challenges of maintaining spatial data. "A Better Way to Handle GIS Data: South Carolina uses server-based GIS" describes how and why the South Carolina Department of Health and Environmental Control adopted a server-based approach to data management. The department found server GIS was not only easier to administer but also provided greater flexibility, which has enabled the department to better meet the needs of its large and complex organization while protecting the confidentiality of the health data it manages.

Harvard University's Geospatial Library (HGL) is a catalog and repository for geospatial data. The Center for Geographic Analysis has employed many strategies to help HGL meet the growing demands for geospatial data by Harvard's increasingly GIS-literate research and teaching staff. Its goal—to make locating and accessing data as easy and flexible as possible—has been achieved through map services, direct access to data maintained in ArcSDE, and the sharing of metadata.

When a large regional energy supplier, Georgia Power Company, adopted an enterprise GIS system, it was faced with the formidable task of migrating its CAD data without compromising data currency or causing disruptions to its workflow. The phased approach it adopted necessitated maintaining two systems, but automation supplied through a custom application effected the transition without requiring additional company resources.

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