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FUTURE PARTNERSHIPS AND THE EVOLUTION OF NSDI ACTIVITIES 48 not exist, a partnership program may develop new software or, preferably, modify or customize existing software. Assuming that these application guides would be available from the clearinghouses through the web (virtual town halls), and could include the needed tools or information on how to get them as well as the ancillary domain- specific datasets needed for application, there should be rapid diffusion of geospatial data use. Partnership programs can be designed to implement this scheme, for example, through the funding of application-specific Community- Federal Information Partnerships grants. These grants could stimulate the creation of application guides as well as the development of needed tools, software customizations, and domain-specific datasets. THE TIME DIMENSION: DATA UPDATE, ARCHIVING, AND CHANGE DETECTION For the NSDI to fulfil its mission, the currency of the data (particularly those themes of the Framework database that exhibit significant change yearly or more frequently, e.g., transportation and orthophotos) must be addressed to assure users that information is accurate as of a specified date, and that the information is not so outdated as to make its use in specific applications problematic. Contributors of Framework data, particularly the changeable themes, should be encouraged and assisted to maintain the data in a structured ongoing process so that some degree of predictability and confidence in terms of the utility and timeliness of key data elements will be assured. Future partnership programs should therefore provide incentives to organizations to establish systems for regular updates and maintenance of Framework data based on transactions. These transactions should include changes to the built environment, such as new roads and subdivisions. Such continuous update activities would provide critical information for emergency 911 systems, and would also significantly reduce the start-up cost for the decennial census. Update guidelines, by theme and perhaps by scale, should be developed to encourage partner organizations to adopt and commit to a regular schedule of updates, with specific definitions of a minimally acceptable update for any particular theme. For example, for the
FUTURE PARTNERSHIPS AND THE EVOLUTION OF NSDI ACTIVITIES 49 transportation theme, certain features and attributes viewed as essential to a large majority of applications would be required to be updated on an annual (or quarterly, etc.) basis, whereas other features and attributes could be updated less frequently. It should be noted that the proposed standard for transportation features accomplishes this by uniquely labeling the points and segments that comprise the road network. This enables one to unambiguously refer to a specific feature and locate it on the earthâs surface. This type of national registry of transportation features would allow for continuous updates and multiple representations. A concurrent effort by the FGDC cultural and demographic subcommittee has developed a proposed standard for assigning addresses to these road segments. It is important to note that in the 1993 report, Toward a Coordinated Spatial Data Infrastructure for the Nation (NRC, 1993), the MSC called for the development and maintenance of a national Street Centerline Spatial Database (SCSD). The SCSD was considered to be one of the cornerstones of the National Spatial Data Infrastructure (NSDI). In 2001, there is no clear program for a coordinated effort to maintain a SCSD. It is also not clear whether input for the continuous monitoring of its proprietary street centerline data should fall in the domain of the USGS, the Bureau of the Census, state highway departments, local governments, or private companies. Partnership programs should be established to develop and test technical and organizational systems for data update. These should contribute to the development of standard protocols and guidelines that would facilitate a high degree of uniformity nationwide. Since many public and private organizations would benefit from accurate and timely spatial data, it is important to consider innovative approaches to public-private funding, and to devise appropriate federal financial incentives that could facilitate the continuous maintenance of framework data. In addition to data update, earlier versions of data must be retained for change analysis and historical review, both of which the availability of datasets representing two or more time periods enables. For example, the Urban Dynamics Research Program (UDRP, 2001), a partnership of the USGS, NASA, and several universities, uses historical land-use data to model and predict urban growth in U.S. metropolitan regions. Other policy issues depend on a
