Executive Summary

This report reaffirms the statements in the Committee on Geodesy (1980) report regarding the need for a multipurpose cadastre at all levels of government in the United States and suggests the outlines of procedures and standards that will be required for its design and implementation. It is intended to assist both the local governments wishing to pursue the development of cadastral records systems for their own counties or equivalent districts and also the many other regional, state, and federal agencies, as well as private businesses, whose participation will be needed.

The basic components of a cadastre are the following:

  1. A spatial reference framework consisting of geodetic control points;

  2. A series of current, accurate, large-scale base maps;

  3. A cadastral overlay that delineates all cadastral parcels and displays a unique identifying number for each of them; and

  4. A series of compatible registers of interests in land parcels keyed to the parcel identifier numbers.

In a multipurpose cadastre, these components must be maintained in a manner that provides the foundation for other registers of land data, each keyed to the standard parcel identifiers for retrieval of specific records and for linking with data in other files. The other files may be in the same jurisdiction or in any other governmental unit that has a multipurpose cadastre system.

Requirements for the geodetic reference framework for a cadastre are summarized



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Executive Summary This report reaffirms the statements in the Committee on Geodesy (1980) report regarding the need for a multipurpose cadastre at all levels of government in the United States and suggests the outlines of procedures and standards that will be required for its design and implementation. It is intended to assist both the local governments wishing to pursue the development of cadastral records systems for their own counties or equivalent districts and also the many other regional, state, and federal agencies, as well as private businesses, whose participation will be needed. The basic components of a cadastre are the following: A spatial reference framework consisting of geodetic control points; A series of current, accurate, large-scale base maps; A cadastral overlay that delineates all cadastral parcels and displays a unique identifying number for each of them; and A series of compatible registers of interests in land parcels keyed to the parcel identifier numbers. In a multipurpose cadastre, these components must be maintained in a manner that provides the foundation for other registers of land data, each keyed to the standard parcel identifiers for retrieval of specific records and for linking with data in other files. The other files may be in the same jurisdiction or in any other governmental unit that has a multipurpose cadastre system. Requirements for the geodetic reference framework for a cadastre are summarized

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in Chapter 2 as: “First, it must permit correlation of real property boundary-line data with topographic, earth science, and other land and land-related data. Second, it must be permanently monumented on the ground so that lines on the maps may be reproduced in the field….” We recommend that the State Plane Coordinate Systems be used as the basis of the multipurpose cadastres in each state. Monumented points of known location on this system should be distributed throughout the area served, at intervals no greater than 0.2 to 0.5 mile in urban areas and I to 2 miles in rural areas. Only a handful of the more than 3000 counties of the United States currently maintain a geodetic reference network with a density adequate to support a multipurpose cadastre. Indeed, in only about 10 percent of the 500 counties designated by the U.S. Department of Commerce as “leading” counties in terms of economic activity is there in place an existing primary geodetic framework of sufficient density (spacing of 3 to 5 miles or less) to serve as the starting point for further densification to a level that would support a cadastre. Significant progress toward establishing multipurpose cadastres thus will require extensive programs of densifying the geodetic control network. Fortunately, several new technologies (described in Chapter 2) for accurately determining the positions of survey control points promise that substantially lower costs per control point will be realized in projects that are organized on a large enough scale to employ them. The base map of a multipurpose cadastre is the primary medium by which cadastral parcels are related to the geodetic reference framework; to major natural and man-made features such as bodies of water, roads, buildings, and fences; to political boundaries; and to each other. The base map also provides the means by which all land-related information may be spatially referenced to cadastral parcels. It is the medium for determining and expressing locations in continuous space, so that shifts in the locations of the boundaries of cadastral parcels may be entered as necessary in the official records. The map may be stored either in graphic form, on paper or Mylar. for example, or in digital form as a “virtual” map. Base maps should be prepared to meet United States National Map Accuracy Standards (see Appendix B). Customary map scales for each type of area (urban, suburban, rural, and resources regions), which are in almost universal use today, are listed in Section 3.4. The cadastral overlay depicts positions of property boundaries in relation to the other features shown on the base map and shows the standard identifier of each parcel, the latter serving as the key to the many other parcel records that can then be based on the multipurpose cadastre. The cadastral overlay could be viewed as a property ownership map that adheres to standards for accuracy of plotting of property boundaries and completeness in display of parcel identifiers—including standards for timely updating to show boundaries and identifiers of newly created parcels. Although the boundary plotted on these maps should meet map accuracy standards,

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it normally does not provide the legal description of the boundary—for the latter, the record of the cadastral survey normally must be consulted. Accuracy standards for the land surveys that support the cadastre should be expressed in terms of boundary tolerances (maximum probable error, in feet or meters) rather than the traditional boundary survey misclosure ratio (e.g., such as 1 part in 10,000). User requirements for cadastral survey accuracy have not yet been clearly established. One recent study for the Maritime Provinces of Canada recommended maximum boundary tolerances of ±0.1 ft in urban areas, ±0.3 ft in suburban areas, and ±1 to ±2 ft in rural areas (see Section 4.2.2). A wide range of governmental functions can benefit from use of the multipurpose cadastre as a complete inventory of all currently existing parcels and their legal identifiers, permitting convenient exchange of data among the users. Twenty-five such functions are listed in Section 5.1.1. The data requirements of the three functions that are predominant users of such data systems—property tax assessment, deed recordation, and planning—are described in some detail. Exchange of land data between systems describing natural phenomena, on the one hand, and cultural phenomena, such as attributes of land parcels, on the other, is greatly facilitated when both are built upon the foundation of a multipurpose cadastre. Within the continuous space that is defined by a cadastre, the boundaries of natural areas can be plotted and compared with those of culturally defined areas. However, most existing natural area data have been compiled without the benefit of this accurate spatial referencing. Until their boundaries are referenced to the same coordinate system in the future, such data exchange will require arbitrary apportionments between natural and cultural areas. The focus of the activity of organizing and operating a multipurpose cadastre will be in the offices of the county government or, in some areas, the municipalities that carry out the equivalents of what are county functions in most states. We recommend that a central office in the government of each county (or municipality, where appropriate) be assigned the responsibility of managing the development of the systems of maps and files that will constitute the multipurpose cadastre for that locality and of compiling the common set of standards for definitions of data elements, accuracy, frequency of updating, and completeness of the records. To assure compatibility these standards should be developed in cooperation with other jurisdictions, including state and federal governments. However, few county governments by themselves have had sufficient resources or the long-range political commitment required to develop a multipurpose cadastre. Assistance from several other sources will be needed, based on their prospective use of the output of the system. Support from state governments will be essential, specifically in (1) organizing the land-records function in county government, (2) mandating the support of a compatible system by units of state and local government and by the private utilities, and (3) providing financial assistance.

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We recommend that a program of federal grants to counties (or their equivalents) be established to provide between 30 and 50 percent of the cost of developing multipurpose cadastres that meet or exceed federal requirements, subject to participation of the state government in the design and partial funding of the program. The cost of a nationwide program of federal financial assistance is estimated at $90 million per year over a 20-year period. High priority should be given to drafting a plan for federal assistance, with a better projection of costs. Support from federal agencies will be important in many aspects of a national program to develop multipurpose cadastres, including the following: Extension of the network of first- and second-order geodetic control points, to provide this basic framework in every county of the United States. Completion of the geodetic framework for the cadastre along the boundaries of federal lands, which in the 30 states covered by the Public Land Survey System will mean retracing, remonumenting, and determining the positions of all quartersection corners along the boundaries of the federal lands, and in the interior of federal lands, where appropriate, with reference to the State Plane Coordinate System. Research and drafting of proposed standards for those components of a multipurpose cadastre for which federal agencies have established expertise, working in conjunction with the national associations of state and local governments in these fields. Requiring compliance by federal agencies and their grantees and contractors with the standards established nationally for large-scale cadastral mapping and cadastral data-base systems or, until such standards are adopted, with the relevant statelevel standards. Multipurpose cadastres will be realized in the United States as much by the coordination of investments currently being made in large-scale mapping and landparcel records, pulling together federal and state as well as local interests, as by increased funding of these activities. Therefore, in conclusion: We urge the National Association of Counties, through its appropriate constituent organizations and staff, to organize a review of the findings and recommendations of this report, involving representatives of local user agencies, and to identify the areas in which more specific standards and procedures are most needed to make the approach described here operational. Examples of cadastral records programs are described in Appendix A to illustrate approaches that seem to be succeeding. They are not the only examples, nor necessarily the best, but nevertheless represent the procedures recommended in this report. These programs are characterized by their commitments to record the locations

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of property boundary corners with reference to a geodetic framework provided by the State Plane Coordinate System and to maintain high standards of quality in building their systems of land records. These case studies are in distinct geographic regions of the United States: East, Midwest, and West. All are in relatively early stages of planning and testing of a records system, although the program in Wisconsin has made substantial progress toward completion of the geodetic reference network. Two of them represent initiatives by regional planning districts, which then depend on county-level governments actually to build and maintain the records systems. Each of the programs also has a number of individual attributes that are exemplary. The program of the regional planning district that includes Milwaukee (Appendix A.1) has been closely tied from the beginning to the processes of surveying and recording of new property boundaries. The program in a suburban county west of Chicago (Appendix A.2) is being managed by the county executive office to support county-operating agencies. The program in the suburban county that adjoins Denver (Appendix A.3) has used the subdivision control process to enlist the resources of land developers in building the system of monumented property lines and the records that locate them with respect to the State Plane Coordinate System. The program of the regional planning district that includes Philadelphia (Appendix A.4) has included the electric and gas companies in the consortium that will develop and use the integrated system.