TERMS OF REFERENCE
Co-Chairs: Ammatzia Peled (Israel) & Antony Cooper (South Africa)
At the 19th International Cartographic Conference and 11th General Assembly of the International Cartographic Association (ICA), held in Ottawa, Canada, from 15 to 21 August 1999, the ICA established a new Working Group on Incremental Updating and Versioning. The reasons for establishing the Working Group are:
Terms of reference
Against this background, the following are the terms of reference for the ICAís Working Group on Incremental Updating and Versioning, for the 1999 to 2003 cycle of work:
Much of the work of the proposed Working Group will take place on-line, though meetings will also be held. It will be crucial to the success of the Working Group and the rapid dissemination of results that the workload of the Working Group be shared between its members. Responsibilities for individual terms of reference will be assigned to different members of the Working Group.
For more information, please see the Working Groupís Web site: http://geo.haifa.ac.il/~icaupd
The following is a brief introduction to the problems to be addressed by this Working Group.
Spatial data bases are already serving as the platform for cartographic production. In the analogue era, the hard-copy maps themselves served also as the data bases for spatial data. Hence, updating the map also meant updating the spatial data set.
In the digital era, the maps should be updated by updating the data base and them producing the new maps. Updating can take place periodically (eg: daily, monthly, annually, etc), as part of a planned updating cycle (with each subset of the data base or each map sheet being updated in rotation), when the amount of change crosses a threshhold, by special request for a specific need (such as an election or census), or other reasons.
There is rapid change taking place all over the world, especially to the types of physical features recorded in spatial data bases. In addition, more and more data are captured for these and other features, as the number of spatial data users, applications and sensors grow.
Thus, there is a need to speed up the frequency of updates and to automate the update processes. To facilitate this, one needs a formalised, continuous and incremental updating process for the digital spatial data bases, and some method of keeping track of the different versions of individual data sets or features. Typically, the updated versions of the data set are then disseminated to the end users by sending them the whole, updated version of the data set or a subset (eg: tiles or layers). Examples of this process are NIMA's Digital Chart of the World (DCW) and road atlases for in-car navigation.
End users tend to use data sets obtained from several different sources, which they often have to integrate themselves, and upon which they build their own value-added data sets. Ultimately, the end user is more concerned about maintaining the integrity, quality and spatial-referencing of their value-added data and topology, in which they have invested much time and money, rather than the external data sets. Yet, these external data sets provide a crucial framework for their value-added data sets.
Hence, when a user receives one of these bulk updates today, they are faced with the dilemma of either ignoring the update (if it is not significant enough) or accepting the update, but with the need to then rebuild their value-added data on top of the updated data set. This rebuilding process involves checking to see if any of the features they have used for geocoding their non-spatial data bases have been changed, aggregated, sub-divided or deleted, and then making the appropriate changes (which can be complex). The update might also result in the loss or change of unique identifiers. It might also be necessary for the user to rebuild the topology of their data base.
Some work has been done on the incremental updating of events, though this is done only to data sets where the users do not add any significant amounts of value-added data, for example, the Electronic Nautical Charts (ENC) of the International Hydrographic Organisation. The Working Group will also consider the work of CERCO, ISO/TC 211, NOTAM (Notice to Airmen), the Open GSI Consortium (OGC) and the European Union Commission V. These types of projects will be used as a starting point for the work of the Working Group.
It is the intention of the proposed Working Group ultimately to take the problem of the incremental updating and versioning of spatial data sets from conception to implementation.