10. Single ISO Harmonized Standard

As noted earlier, use of a profile to SDTS is one method to achieve harmonization with other standards such as BIIF, DIGEST-VPF, CEN GDF, IHO S-57 (formerly DX-90), SAIF, or NTF-BS7567. Moellering and Hogan (1996) provide details on the major national and international spatial data transfer standards. As these and other standards vie for approval at the international level by the International Organization for Standardization (ISO) there may be strong effort to harmonize or reconcile competing spatial data exchange standards into a single standard.

The American National Standards Institute (ANSI) National Committee for Information Technology Standards (NCITS, pronounced "insights) technical committee L1 (for GIS) is considering SDTS as an ANSI standard. ANSI NCITS L1 is also the U.S. Technical Advisory Group (TAG) to the ISO Technical Committee on Geographic Information / Geomatics (TC 211). ISO TC 211 will consider international standards for spatial data transfer. Use of SDTS as a national standard in Australia, New Zealand, South Korea, and the US insures that SDTS will receive consideration by TC 211. Because of the configurable nature of SDTS and its many options, and because it has been harmonized with several other standards through documented profiles, it may become an "umbrella" standard under which more specific standards can reside. Note also that ISO-8211 is used as the physical implementation of many of these standards, including SDTS.

A single ISO standard should include the best characteristics of the current group of national and international spatial data standards. Version 3 of IHO S-57 now includes "incremental transfers" that allow the exchange of only information that has changed. Multi-scale representation capabilities are now available in CEN GDF. Sophisticated indexing, subtiling, and access capabilities are now used in VPF to support direct exploitation. Support for multiple levels of topology and multiple data models (including raster) within one data transfer is similar to current DIGEST capabilities. These characteristics will be included in the proposed object-based profile to SDTS (see next section), which should be useful as we approach ISO harmonization.

Other harmonization efforts are also being investigated. One is between DIGEST and GDF. The hydrographic, bathymetric, and maritime community (IHO, IMO, NIMA, NOAA, Coast Guard, CHS, FGDC Bathymetric Subcommittee) is also interested in a reconciliation of standards for vector nautical charts for Electronic Chart Display & Information Systems (ECDIS), including S-57 (formerly DX-90), DIGEST, and VPF used for DNC.

A single, harmonized ISO standard for spatial data exchange and archive, possibly using SDTS as an "umbrella," would be of great value for several reasons. It could remove much of the need for multiple SDTS profiles that are nation specific or that are used to harmonize SDTS with other standards. Use of an object-based approach or profile should also help remove the need for multiple profiles linked to data models and schemas. Data sharing will be easier if the number of profiles is small.