Many international regions, countries, states, and counties throughout the world have spent considerable resources over the past few years implementing and managing Spatial Data Clearinghouses (SDCs). These SDCs are prominent features of Spatial Data Infrastructures (SDIs) (Clinton 1994, Federal Geographic Data Committee 1997, Onsrud 1998, Crompvoets et al. 2004), because they are the facilities for making spatial data accessible to the general public and promoting data sharing. SDCs facilitate the searching, viewing, transferring, ordering, publishing, and/or disseminating of spatial data and services from numerous sources via a Web site (interface) on the Internet, and, as appropriate, providing complementary services. These SDCs contain data catalogs, which are access systems that use metadata (INSPIRE Architecture and Standards working group 2002, Maguire and Longley 2005, Tait 2005).
The access service for spatial data on the Web is known variously within the spatial community as clearinghouse, catalog service, spatial data directory, geoportal and geospatial one-stop portal. Although different names are used, obviously the goals of accessing spatial data through the metadata remain the same (Crompvoets et al. 2004, Beaumont et al. 2005). The enhancement of data/service accessibility and the sharing of spatial data and related services between suppliers and users are the main reasons to build these electronic facilities (Bernard et al. 2005, Beaumont et al. 2005, Maguire and Longley 2005).
Based on an overall assessment, the average cost of an SDC is approximately ??1,500,000 a year (Southern California Association of Governments 1998, INSPIRE Architecture and Standards working group 2002, Pasca et al. 2004). This money is spent on management and coordination costs, GIS and Internet application development, training, hardware, standardization activities, legal environment creation, and metadata preparation. Currently, about 500 (noncorporate) SDCs have been established and many more SDCs probably will be set up in the future. On a global scale, hundreds of millions of dollars are spent yearly on SDC activities. Up to now this large investment has rarely been audited or evaluated. A study conducted by the Urban and Regional Information Systems Association (Gillespie 2000) cited that while the costs of SDC projects may be relatively easy to assess and highly "front-loaded," the benefits are often difficult to measure and may not emerge until well into the life of the SDC and depend on other factors coming into play (Federal Geographic Data Committee 2002, Commission of the European Communities 2004).
SDCs could be developed at different administrative levels, ranging from local to state/provincial, national, and international levels to a global level, to better access and share spatial data and related services. There is a need to address politicians and decision makers to demonstrate the benefits of such a system. One of the difficulties of selling the benefits to decision makers has been the paucity of systematic evidence of the full economic, social, and environmental impacts. This was highlighted in the context of Geospatial One-Stop (Federal Geographic Data Committee 2002) and the Extended Impact Assessment of the INSPIRE-initiative (Commission of the European Commission 2004). However, it has been difficult to extrapolate impacts from these individual cases to reach more generalized conclusions. In addition, it is critical to move away from a narrow focus on the technical considerations of SDCs to their potential contribution to area competitiveness, innovation, productivity, job creation, etc. (Craglia et al. 2003).
The focus of this paper is on the worldwide impact assessment of the current SDCs with the main objective of providing this information to policy makers to assist them in evaluating whether or not investment in setting up and maintaining these SDCs is justified. …