operations is just for parcel data maintenance costs, or what factors contribute to these costs, are difficult to estimate accurately on a nationwide basis. For this reason, the FGDC Subcommittee for Cadastral Data does not provide an estimate of these costs. This committee did a preliminary analysis of what maintenance costs might be based on several different methods. However, like the FGDC subcommittee, it was found that the cost of maintenance depends on so many factors (size of the county, how quickly the county is growing, who is maintaining the data) that a reasonable estimate could not be developed. Nevertheless, in terms of a national system for land parcel data, the costs of maintaining the data will in most cases be borne by the data stewards as a cost of doing business. The challenge will be in supporting those local government entities that cannot afford to maintain or publish the updated attributes needed for a national system in digital format. In some cases, states have already stepped in to cover this function for counties that are unable to do so.

Finally, there are costs for creating nationally integrated data that go above and beyond the development of the original parcel data costs. For example, there are costs associated with edge-matching parcel boundaries along county and state borders and reconciling public and private lands. Some of this work has already been done as regional groups or states have been compiling parcel data sets for their areas. Private industry has also had to address this issue as it has begun building parcel data systems. Another element of the cost would be to establish an infrastructure for accessing the most current data from the parcel producers and making them available in a seamless format. Systems with these capabilities exist for other purposes, so the major challenge is to find a source of funding. Finally, costs would be incurred to support the national coordination function. All of these elements of a national land parcel data system would most likely have to come from new funding.

Therefore, financial challenges must be addressed for the production of the initial parcel data coverage, the integration to make the data nationally consistent, and the infrastructure to make the data accessible. There is a concern among parcel data producers as to who would bear these costs, as illustrated by the comment below:

Managing parcels for a county of 600,000 people is already difficult. I do not believe that the overhead of complying with a national mandate will provide, at the producer level, any benefits. Therefore I see the potential for increased costs and overhead, as a potential liability. (Comment from web forum: Stephen Marsh, Director, GIS Department, Jackson County, Missouri)

The big question is how to assemble the collective interest in parcel data to financially support a national land parcel data system that covers every part of the country. Ideally, all stakeholders would contribute to the program. A representative from Zillow told the committee at the Land Parcel Data Summit that it encounters major problems with acquiring consistent data from local governments at a consistent price. Zillow is willing to help support the production of parcel data but would like to see a reasonable and consistent price for it. Although there seem to be potential sources of funding, the committee recognizes that coordinating these opportunities and partnerships and developing an equitable funding model will be a challenge.


Data Sharing Restrictions

Even though data about land ownership and value are considered to be public information, a number of barriers inhibit the exchange of parcel-related data. Since land parcel data are the basis of many legal and economic decisions within a community, they are also likely to have restrictive policies regarding licensing and distribution. The importance of these distribution issues was covered at length in the NRC report Licensing Geographic Data and Services (NRC, 2004a). It is

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