5 GEOGRAPHIC INFORMATION SYSTEMS

The HHTIS is then integrated into a larger geographic information system. GIS is a method to display information in a geographic output or to link information to an actual location on the earth. Unlike a paper map, where what you see is what you get, a GIS map can instantly combine or hide layers of information to provide greater analysis capacity and instant access to details about the features on the map. Working with DPR and the City of New York, the Trust has access to the GIS base-map layers developed for the management of the city. These layers of information include such typical map sets as streets, buildings, topography, zip codes, political boundaries, census information, and tax parcels. Using data from the HHTIS, GIS provides a whole new context in which historic resources can be analyzed. Whether the scale is citywide or site-specific, a broader understanding of resources can be attained. The Trust is using the GIS software ArcView created by ESRI.

5.1 GIS: CITYWIDE SCALE

Managing cultural resources on a citywide scale is a challenge, but using a GIS provides clear trends and a new context for stewardship. GIS is more than just locating a structure on a map. It is the comparison of that structure to other historic houses; it is the analysis of the structure and how the structure relates to its neighborhood, city, history, and environment. Citywide analysis can take many forms, including visitation and community demographics, membership analysis, inventory management, and analysis of structures and conditions based on different geopolitical areas.

The interactions of political districts are quite complex, and funding can come from any level: community boards, city council, borough presidents, citywide offices, and state and federal districts. Geographic analysis of resources and districts plays a vital role in the Trust's work processes. For example, GIS allows the Trust to analyze the number of National Historic Landmarks with wood-shingle roofs in poor condition in a certain city council district or state representative district. Then, when additional information is needed, a click of the mouse brings up data from the HHTIS or even digital photographs. This flexibility provides the Trust the ability to work with multiple political entities for the protection of these resources.

A number of scenarios of citywide analysis are possible. Structures requiring oil deliveries can be identified, and physical maps and directions to the houses can be created. Membership campaigns can be enhanced through a geographic understanding of where current members are located and where members are absent. In a similar manner, the Trust can analyze school visitation and participation in programs at the houses to determine which school districts are or are not responsive to house programming. These examples just scratch the surface of how the Trust uses GIS for citywide management of the historic sites.

5.2 GIS: SITE-SPECIFIC USES

Site-specific analysis is also enhanced as GIS provides a framework for understanding the site. Currently available information provides such data as topography, structures, and building heights. Data from the HHTIS are available for analysis so facade conditions can be viewed in correlation to a building's physical environment. Through a method known as “hotlinking,” any digital file can be accessed with the click of a mouse: digital images, digitized historic images, or even digitized Historic Structure Reports or other important planning documents.

The study of cultural landscapes and archaeological sites continues to be advanced through the use of GIS. Features in the landscape, whether historic or modern, are identified and integrated into the system. Historic data about these features, entered into the HHTIS and available through the GIS, provide a deeper understanding of the evolution of the site. Digitized historic maps are then used as base maps for further analysis of these features to continue to study the evolution of the cultural landscape. Using the historic base maps and the GIS, potential archaeological exploration can be identified and integrated into the management plans for a site. The location of previous excavations can be entered as well, allowing the Trust to assess the archaeological impacts of site improvements and maintenance on the grounds.

The Trust is also pursuing the use of GIS to synthesize many different types of information needed for the analysis of interiors. Using floor plans as the base map, the GIS can integrate current digital images, historic images, data from the HHTIS regarding interior architectural features and conditions, information from furnishing plans, and, finally, data from the collection management software. This tool would enable the Trust curator to sort through the different resources and information types, all in the GIS, to create a better understanding of the interior conditions and to analyze current furnishings versus historical furnishings.

5.3 GIS: CAD INTEGRATION

The detailed line drawings of a computer-aided design (CAD) file can be easily integrated in a GIS. The benefit lies in the ability to combine the detailed CAD drawings with the analysis capabilities of GIS. In certain cases at the Trust, CAD drawings have been integrated with the GIS, most commonly in the form of site plans to fully document current conditions at the sites. CAD and GIS have been used for preservation planning for structures and sites to an increasing extent in recent years, enabling analysis of a full range of conditions and solutions or even predictive modeling of future deterioration. The Trust is moving toward the implementation of CAD-GIS for its advanced preservation efforts and surveys. This application is in development at the time of this article.

5.4 GIS: FUTURE IMPLEMENTATION

There are many plans for the future implementation of the GIS. The Trust will continue to share information with DPR, striving for the most efficient management of the structures. Sharing data with DPR connects the Trust to the citywide implementation of GIS for facility management. In this environment, for example, the Trust will work with the police and fire departments to improve emergency response. With access to GIS maps at the 911 switchboard, operators will be able to accurately locate structures and route emergency vehicles even if they are located within a park area. In the office, the Trust will continue to develop and use GIS for a number of different applications. Future implementation includes continued analysis of cultural landscapes, archaeological resources, exterior conditions, interior conditions and furnishings, and visitation and membership demographics. The Trust is planning for further integration with CAD for increased survey and analysis capabilities, three-dimensional modeling of the structures and sites, and Web-based formats for public access to certain aspects of the information.