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6 Conclusions One of the powerful forces steering the development of information systems is the heuristic power potential of spatial analysis. Even the limited experience to date of overlaying data layers and analyzing spatial interrelationships among these data layers has aroused high expectations. The technology to perform this work is already available at ever-decreasing costs. The emerging technology of precise positioning promises to provide the coordinates needed to link data layers within these systems in the near future. Such geographic information systems encompass many large, coordinate-based data files. It has become painfully apparent that the application of spatial analysis to the diverse and complex tasks of managing federal land resources has been much delayed. One major factor accounting for this delay is the nature of the cadastral surveying tradition in the United States, which places high value on boundary monuments and locally referenced survey measurements and little or no value on coordinate-based reference points connected to the national geodetic network. The federal cadastral interests are defined by the Public Land Survey Sys- tem (PLSS) and the township, section, and quarter-section corners. These interests are recognized to be large and complex because of the extensive areas of federal land ownership, the vast resources, and the often complex spatial pattern of fractured rights and easements. Close examination of the federal interests reveals a complex spatial pattern at the interface between federal and nonfederal lands. The interspersion of private holdings within federal lands contributes to this complexity. The Committee realized that the prospects of integrating land records 65

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66 MODERNIZATION OF THE PUBLIC LAND SURVEY SYSTEM contained in federal topographic, geodetic, and cadastral files were unlikely as long as cadastral records and data lacked a coordinate basis in the PLSS areas. The Commiteee recognizes the PLSS as a national resource of immense importance that needs to be preserved to protect property ownership rights in federally owned areas, along the federal-private interface, and on patented lands. The present condition of the PLSS iS poor, and deterioration continues to diminish the condition of the system. Efforts to maintain the system have low priority virtually everywhere. Vigorous steps to restore and maintain the PLSS are needed. The Department of the Interior should clarify the responsibilities for Public Land Survey System (PLSSJ maintenance. The Commitee recommends that the Department conduct investigations into the present condition and future role of the PLSS. This should include a review of federal law and authorities, state and local law and authorities, the condition of PLSS records within state and local government, and state and local programs and private and semipublic activities affecting modernization of the PLSS. The goals of the multipurpose cadastre and the concommitant tasks of integrating spatial data files led the Committee to conclude that a program is needed that goes well beyond mere maintenance to include modernization of the PASS. This modernization program would take full advantage of the accuracy achievements together with the time and cost economies of the emerging positioning technology to establish precise coordinates for monu- mented PLSS corners. These corners would then be integrated into the national horizontal control network. The Bureau of Land Management (BLM) is urged to change priorities, procedures, and standards to establish coordi- nates that meet recommended multipurpose cadastre standards for corners on federal-private interface lands. Over time this would ensure that the survey work that needed to be done in any case would have additional utility because it met multipurpose cadastre recommended standards. These same standards and practices extended to all federally funded survey projects would further advance progress toward the multipurpose cadastre. The Committee recognized a need to develop a PLSS digital coordinate file to serve a variety of present and potential needs. This file could encompass PLSS section corner locations that meet positional standards defined by National Map Accuracy Standards extractable at modest cost from the National Cartographic Data Base. In fact, the National Mapping Division is currently including a PASS data layer as part of the Digital Line Graph file development. The need for such data for purposes of display and spatial analysis is already evident and can be expected to grow as interest in geo- graphic information systems expands. Over time, this PASS file would ac- cumulate coordinates of progressively higher quality and thus support the multipurpose cadastre effort.

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Conclusions 67 Demand for PLSS coordinate data could only be assessed in a preliminary way. At the coarse end of the position accuracy spectrum there is clear evi- dence of demand, chiefly among users involved in linking natural-resource records to base maps for purposes of spatial analysis. Their accuracy needs are satisfied by the National Map Accuracy Standards governing the con- struction of the National Cartographic Data Base. At the fine end of this positional accuracy spectrum, on the other hand, are the federal program managers who require clear spatial definition of their areas of responsibility. The present lack of jurisdictional clarity is a costly drain on program resources and time. This federal user group is merely a subset of the client group en- visaged for the national multipurpose cadastre. It is curious that no user group was identified for intermediate positional accuracy standards. This broad gap might well reflect the paucity of base maps and resource inven- tories between the 1:24,000 scale used for the 7.5-minute topographic series and the fragmentary local surveys at cadastral scales. The Committee recommends that responsibility for establishing and main- taining a national digital coordinate Public Land Survey System (PLssJ data base be placed with the Bureau of Land Management in cooperation with the National Geodetic Survey. This file should include data on the source and estimated accuracy of each position. We recommend that the Office of Land Information Systems, proposed in the report Need for a Multipurpose Cadas- tre (Committee on Geodesy, 1980J, be established in each state and be re- sponsible for maintaining a file of PLSS corner coordinates determined by state or local units according to national standards established by the Bureau of Land Management. We recommend that the Department of the Interior develop mechanisms whereby private and semipublic units can contribute PLSS corner coordinate data to the file maintained by the proposed State Offices of Land Information Systems. To facilitate the task of integrating spatial data files, the Committee rec- ommends that the Department of the Interior report on the positional ac- curacies of all PLSS corners and on the positional accuracies and spatial resolution of all their resource inventory files. We recommend that the Cadastral Survey Division of the Bureau of Land Management express survey results in terms of point accuracies as well as closures. We also recommend that all agencies contributing data to the PrSS digital coordinate data base assess and maintain records on the unit cost and accuracy of the coordinates they derive.