Thus the governments decided of the collection of the information in the types and formats that were required for its intended applications. Applications did not vary much across borders, and therefore were developed in many countries a similar range of products, a typical list being:
Moreover, needs across borders being very comparable, national products across borders were also quite similar, and if edge-matching was not always evident, anyone from country 'A' would be able to read and use a paper map from country 'B with no special effort required. Thus tacit cross-border interoperability also existed.
GIS technology has changed all that, particularly with the development of desktop GIS. Usage and type of applications is now incredibly diverse. GI has become a mass-market product on its own or is found integrated in hard- and software solutions. Nearly anyone can create their own maps, thanks to the use of desktop mapping, GIS, GPS surveying, satellite imagery, scanning and intelligent software. The old monopoly is shaken.
GIS technology is been employed in many different areas and in newer fields of applications, as computer hardware and GIS software applications provide improved capabilities at reduced cost. However, the overall cost of developing geospatial data required to support GIS applications remains relatively high compared with the hardware and software required for GIS.
In addition, GIS users tend to develop their own data sets, even if there are existing geospatial data sets available for them, because:
Most GIS applications employ a limited number of common geospatial data items, including geodetic control points, transportation networks, hydrological networks, contour lines and so forth. These items are common to many GIS applications and provide keys for the integration of other and more specialized thematic information. They represent the content found in most traditional base-maps, or in modern technology and terminology, in most GI databases and products. Does that mean that these items are the 'core'? What about postal addresses? What about cadastral parcels?
The concepts of 'core-data' and of 'reference-data' relate to two quite different perspectives. But fortunately they may result in the definition of very similar specifications. Let's start with 'reference'. The primary reference for cartographers is the geodetic and levelling networks that give the surveyors the physical links to a co-ordinate system. Of course, this has recently and dramatically changed with satellite positioning technologies, but the principle remains that the primary reference is what gives access to geodetic coordinates. We are not really concerned with this type of reference here, because it is generally not a part of the Geographic Information that is used in GIS applications, but rather its background. Very often it is even not visible.
If geodesy is the reference for the cartographer and the surveyor, the 'reference' of the GI user is generally more closely related to the real world. It includes concrete themes, such as infrastructure - roads, railways, power-lines, settlements, etc, or physical features - terrain elevation, hydrography, etc. It includes also less tangible features, that have nonetheless a significant role in human life: administrative boundaries, cadastral parcels, gazetteer, postal addresses, etc. All these features are keys that allow one to relate, to 'refer', external information to the real world, through the media of its GI representation. Therefore they may be considered as comprising a reference for the GI user -- the 'reference data'.
A different perspective presides over the conceptual approach of the 'core data'. The core being the heart, the central part, the fundamental part, it may be also considered as being the common denominator of all GI data sets, being so because being used by most applications. We can see that this perspective can bring the specifications of the core very compatible with those deriving from the concept of the 'reference data'. Therefore, let's not loose ourselves in academic debates, and let's keep here a simple practical view and terminology.
'Core data' when used here, will mean "a set of Geographic Information that is necessary for optimal use of most GIS applications, i.e. that is a sufficient reference for most geo-located data." The relevance of this definition can of course be questioned, and will need to be improved. Let's adopt it only for the sake of understanding the following chapters. One obvious necessary accommodation to the above definition, is that the specifications might be scale-dependent. Core, then, may refer to the fewest number of features and characteristics required to represent a given data theme.
We have seen before that the GIS revolution has resulted in a democratisation of GI, but also in a key problem that is the non-interoperability of the GI produced with the new technologies. We propose that the concept of the 'core data' is one instrumentality to help improving interoperability, thus increasing GI usability and reducing expenses resulting from the current duplications.
Interoperability complications exist at different levels, and they can be found in four main types:
The concept of the core aims at sharing the core data sets between users in order to facilitate the development of GIS. Each data item may be provided by a different data provider. Such data providers produce data through their daily businesses including road management, urban planning, land management, tax collection, and so forth. Although there may be many data providers, the data sets they provide must be integrated to develop core data sets. Once these core data sets are shared between data users, each user does not have to develop the core data by oneself, and can avoid duplicated efforts of core data development. Consequently, by sharing the cost of developing the core data, data development cost can be minimised and shared between users.
Much more than at the time of data set creation, the benefits of the 'core data' concept will be revealed when updating. Since these core data sets are developed by those who produce the data through their daily businesses, they are updated most frequently. Therefore, the users are assured of using up-to-date core data sets. In addition, these data producers develop most detailed geospatial data with high quality based on their business requirements. Another benefit of using core data sets lies in the fact that these commonly used core data sets enable the users to easily share other geospatial data with other users.
Achieving Benefits
In order to achieve those benefits described in the previous section, those data producers who develop and maintain geospatial data sets through their daily businesses are to distribute their data to the public. Once distributed, GIS users can collect and integrate them in their own GIS applications. Such data sets would provide GIS users with the most up-to-date and highest quality data sets publicly available. Hence the users have to spend only a minimum amount of cost for the core data in their GIS applications.
Global Map is an illustration of 'core' data sets. The Japanese Geographical Survey Institute took in 1992 an initiative in developing global geospatial data (Global Map) to cope with the global environmental problems. The goal is to involve national mapping organisations to collaboratively develop global geospatial data sets. By incorporating national mapping organisations of the world, the collected information would be most up-to-date and assured of being free of national security issues. The Global Map could be considered as an initial implementation of the concept of a suite of 'core data' for GSDI in concert with similar framework data sets at regional and national levels.
Chapter Two | Context and Rationale | Organisational Approach | Implementation Approach