all types of data layers are used by everybody, but at the state, tribal nation, city, and county levels some additional themes are used by a great number of users. In such cases, it may make sense to incorporate these additional data themes into an extended Framework, incorporating all fundamental data layers identified for the cities, counties, tribal nations, states, and the nation.

In general, one would expect that data layers might require increasingly finer resolution and perhaps a greater amount of data detail at the city or county level than at the state or tribal nation level. The same may be true of the state or tribal nation level compared to the national level. Of course, some data layers may have the identical resolution and data detail in more than one of the three geographic levels (nation, state or tribal, local). The committee developed a matrix that attempts to examine the responsibility for the creation and maintenance of different framework data layers (Table 1). The data layers are the ones mentioned in the National Academy of Public Administration’s 1998 publication, Geographic Information for the 21st Century (NAPA, 1998). The intent of this matrix is simply to demonstrate that the NSDI must be built on the basis of shared responsibilities, costs, benefits, and control. The committee recognizes that responsibilities will vary across the country depending on available resources and differing mandates and regulations, as well as property ownership, density of development, and other factors.

The matrix could serve as a useful starting point for the development of an extended framework. Preliminary designations of primary and supplementary responsibilities for each layer are indicated. It should be noted that orthoimagery is viewed as a critical component of the development of any extended Framework data collection effort. The ultimate responsibility for the creation and maintenance of any individual theme would be determined by the legislative or regulatory mandates in a particular region. It must be acknowledged that local government requirements for zoning, property assessment, or other land-use decisions will often determine where such authority resides. Some local governments have been able to couple these mandates with the requisite financial resources to develop such systems independent of other organizations. The chal



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