Henri J.G.L. Aalders
Faculty Civil Engineering and Geosciences
Subfaculty of Geodetic Engineering
Delft University of Technology
Faculty of Applied Sciences
Katholieke Universiteit Leuven
E-mail: h.aalders@geo.tudelft.nl

Keywords: Information Technology GIS, GIS Data communication, Metadata

Since geographic data is expensive to obtain, it is shared by many different users. More and more the transfer of geographic data is done by Internet requiring a Geographic Information Infrastructure in a national environment. For users a national GII should consist of policies, techniques, participants and standards, assuming the Internet is available, in order to make the content of the geographic information clear and available for them.

It is very well known by users that geographic data has some important characteristics that distinguish them from other type of data: usually its volume is huge and the capture is very cumbersome and expensive. Nevertheless it is applied in many different scientific fields such as regional and town planning, infra-structural engineering, property registration and valuation, decision support systems, etc. Therefore users of geographic data share existing data; even when the available data is not exactly what is required.

Until recently, for the dissemination of geographic data no system existed and users were dependant on knowledge of existence of datasets they might be able to use. With the rapid growth of the use of Internet a new phenomena was created: directory and dictionary data about existing datasets are listed with reference to the validity, quality and content of the datasets. Sometimes the Internet also enables to convey datasets form the supplier towards a recipient that are requested by a potential user. And so a new infra-structure was developed for geographic data.

Some countries in Europe are developing a Geographic Information Infrastructure (GII). They are stimulated by the developments in the United States of America and supported by EUROGI the Umbrella Organisation for Geographic Information within Europe. The Geographic Information Infrastructure consist of the development of:

• hard- and software for electronic communication according to the seven stages of the ISO interconnection model (see table 1, [Worboys, 1995]). In this article only the logical and organisational stages are discussed;
• clearinghouse. The idea of a clearinghouse [Bogaerts, et al., 1997] comes from the financial world.
• With respect to the financial transactions between banks, the clearinghouse keeps the data on mutual indebted amounts. At the end of the day the banks are informed about the data of the final amounts to be transferred between banks. So every day there is a ‘clearing’ between the banks. A clearinghouse for geo-information keeps metadata from different organisations and makes them available. It is obvious a metadata standard is required for this.
• In the Geo-IT area a clearinghouse can be described as an electronic desk that can be contacted by digital communication channels (e.g. Internet) to obtain information what data are available and indicating the conditions and restrictions for transfer. In some cases also the data themselves can be obtained through the clearinghouse;
• management and policies of an information structure. The participation in the clearinghouse by organisations has several aspects to be achieved:
• increase the amount of participating organisations in order to create a wide availability through the clearinghouse;
• improve the service offered to the participating organisations and the users of the clearinghouse, i.e. not only to give information about data through the clearinghouse but also making the data available;
• make agreements for billing and fees to be for the services offered.
• data framework giving a structure of the data to make them accessible for users. The contents and as such query of data in the clearinghouse may exist of availability in the clearinghouse:

1. only metadata. The actual data can be obtained by other connections that are described by the metadata either off-line by tape or discs, or by electronic means;
2. metadata about all accessible data and core databases as geodetic control data and elementary topographic data with administrative boundaries, rivers, roads and railroads, height, mayor cities, landuse, addressing systems, etc. Other data can be obtained by other means from the providers mentioned in the metadata in the clearinghouse or be combined with the user specific data;
3. metadata and geo-databases itself;

• standards for the transfer and query of data.

Around 1900 the technical standardisation became into development (e.g. BSI 1901) and nowadays almost all European countries have national standardisation institutes and eighteen of them are members of the CEN (Comité Européen de Normalization, Brussels in Belgium) i.e. Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, The Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Globally there exists the ISO (International Standard Organisation, Geneva in Switzerland). For the standardisation for Electronics and Telecommunications there exist a separate network of standardisation institutes.

The EC council decided in 1986 (decision 87/95/EC) on the application of European standards at international level.

Some of the aims for standardisation are (including the indications to GIS/LIS relevance):

• quality improvement. Many data in GIS are of different homogeneity. In order to improve the intrinsic relative quality clear and well, defined quality concepts can be applied;
• efficiency. Standards will lead to the improvement of the data transfer avoiding duplication of the expensive data capture and processing;
• to avoid information loss. Common standards will avoid the loss of information that occurs when transforming data from one system into another;
• knowledge transfer. Standards contribute to clarify the different aspects of all applications concerned. Users will understand their mutual requirements better when transforming from one to another system.

Except for English, in which language only the terms standard and standardisation exists, in many languages also the terms 'norms' and 'normalisation' is used, often as synonym, although they may describe different concepts. Whenever both words occur in a language, the word standard has usually a wider meaning:

• norms (and normalisation, as the process to produce norms) is used for the official defined agreements that are applied, while
• standards (and standardisation, as the process to produce standards) is used for all type of agreements between users for mutual data transfer.

In general the term ‘data exchange’ should be avoided: multiple use of geographic data implies that data goes from one user to another (transfer) and no data returns back from the recipient to the original sender. So usually nothing is exchanged but only transferred; in cases where exchange of data does really take place, i.e. data goes from sender to recipient and the recipient sends (even if it is the same) data in return one may also speak about a bi-directional data transfer.

Also one should distinguish between the standardisation of data as opposed to the standardisation of the processes. One should realise that no standardisation of processes is possible without the standardisation of the data (see fig. 1).

However, in many cases the standardisation of processes will reflect quality control applying the ISO 9000 series of standards for defining requirements in the different sub-processes in order to certify the quality of the end products.

It is difficult to determine the best moment introducing a standard. Obviously standards are required whenever user(s) have a need for it. But at the time that parties involved feel the need to introduce a standard in their application, they have undergone such a high level of development that the implementation of a new standard will create a fall-back in application or at least will be experienced as annoying to an experienced user, while a new user will not easily understand why standards should be developed let alone be applied. However, one should always realise that standards will create many new possibilities seen from a more general point of view in the arena of geo-information.

Besides, in the field of IT, also in the Geo-IT standards have been applied very successfully, including graphics standards which are also of great importance to the field of GIS: many systems use PHIGGS, DXF, IGES, etc.

When applying digital geographic data many other aspects such as semantics, metadata (including quality) geometry, transformations data, (topo-)logical consistency and currency will also be subject to transfer. Envisaging the "greater Europe" as an important political and governmental institution, the transfer of data across the national boundaries will become apparent requiring the development of European standards in the field of geography.

On the national level standardisation takes place at different levels:

• (inter)national level for generic agreements between parties;
• branch level for agreements between institutions of their specific common application and data;
• internal institutional level, where internal processes are aligned through data and procedure definitions.

Globally standardisation in the field of geographic information is concentrated in CEN/TC 287 and ISO/TC 211.

The EC stimulates the developments of European standards. Information technology and telecommunications are of utmost importance for de economical and social development of present Europe: a common European market will not evolve when the necessary information transfer will be hindered by technological constraints.

Large amounts of money are spent in the field of information technology and telecommunications. Examples are the ESPRIT and RACE programmes, where ESPRIT is directed towards the development and introduction of standards while the RACE programme focuses on telecommunication.

Since at the end of the seventies in Germany the first standard in the field of Geo-IT was designed, many countries have followed this [Moellering 1991]. Apart from developments in the different countries in Europe and in international bodies (see table 2), in 1991 the CEN started the development of a set of standards in the field of geo-information after a proposal from AFNOR, French member of CEN. This work is done in the technical committee CEN/TC 287 "Geographic Information.

The first standards (Reference Model and Geometry) has been issued in August 1997 as ENV; standards on metadata, quality, position, geographic identifiers are expected in 1998. In 1999 a reconsideration of the ENV’s will start, whether they will reach the EN status or whether they have first to be revised. For this consideration it is expected that the ISO standards will be available and taken into the consideration. In the development of standards CEN/TC 287 had liaison to:

• CEN/TC 278. One should be aware that CEN has another technical committee that uses geographic information models: CEN/TC 278 on "Road transport and traffic telematics" which was founded some time earlier Based on the EC DRIVE programme and the CEN/TC 278 most recent standards proposal was issued in March 1996 called prENV 14825. In this standard a geometry model for networks was developed which differs from the proposals of CEN/TC 287. Recently, both TC's has agreed to align their work in order to end up with one and the same model for the common fields of concern;
• The European Committee, especially DG VII - Directorate General for Transport and DG XIII - Directorate General for Telecommunication, Information Market and Research - promoted standardisation early nineties for the increasing use within geo-information. As a result the EC has prescribed that all project of the DRIVE program will have to use the CEN/TC 278 standard, including the RADEF project (Road Administration Data Exchange Format). RADEF promote the transfer of road data between the EC, national, regional and local authorities, and firms that work in the field of transport and road administration;
• EUROGI (EURopean Organisation for Geographic Information),which is an umbrella European organisation that promotes and tries to harmonise the standardisation of geographic information as part of the European geo-infrastructure. EUROGI is involved in different Geographic Information related policy areas as:
• knowledge promotion of existing standards;
• harmonising and implementing of standards;
• identification of missing standard and promote their development
• create a forum for debate about these issues;
• increasing the awareness of juridical/organisation issues in geo-information;
• increase the political support in the use of geo-information;
• CERCO/MEGRIN. Comité Européen des Responsables de la Cartographie Officielle has initiated the Multi-purpose European Ground Related Information Network to provide the most efficient way of data transfer for existing and future data from national mapping authorities and private parties in surveying and mapping, road and transport administration and industry. From 1991 -1996 a small working group of MEGRIN has performed field tests using existing and planned standards for these standards and transfer methods in order to develop transfer and standards concepts;

• ISO/TC 211 started in 1994. Because of mutual interest in the same field of development both TC's have agreed to co-operate where possible. Also the so-called Vienna agreement between CEN and ISO is valid and so both TC's have representative in their committees and also several persons work in the both committees. Since CEN/TC 278 has started earlier as ISO/TC 211 it has more progressed in developing transfer standards.
• ISO/TC 211 uses the CEN/TC 287 standards as input for their developments but starts from a different point of view: CEN/TC 287 develops standards from an object based point of view, while ISO/TC 211 develops standards from a interactive and process based point of view stressing the universal application of geo-information, GIS-functionality and information management and services. However, this can only be done when the object based standards are available (see fig. 1).

All the aspects mentioned above should be given enough attention to ensure the quality and accessibility of the GII system of and the data in the clearinghouse as well for the participating organisations providing the data in the clearinghouse as for the users of the clearinghouse asking for information. From the previous it may become clear that at least the use of a complete metadata standard for a GII is inevitable.

In the following some example are given of existing clearinghouses showing the different solutions of some example National GII systems, in increasing order of complexity:

In 1995, the RAVI (Overlegorgaan voor de Vastgoedinformatie) initiated the development of a National Clearinghouse for Geo-Information (NCGI) on proposal of the Geo-IT sector as ministries, research institutes, Netherlands Cadastral Registry, Central Bureau of Statistics and local and provincial authorities. Politicians as the co-ordinating Minister of Housing, Spatial Planning and Environment for landinformation and parliament members showed much interest and support for the initiative. In pilot project a bottom-up strategy was chosen to involve the future user optimal and the extract signals from the Geo-IT sector at an early stage.

At present the clearinghouse provides metadata of datasets of participants using the definitions in the CEN prENV 12657 ‘Geographic Information - Data description - Metadata’. The actual data has to be accessed by contacting either the distributor, or retrieve the data from files that are described through the clearinghouse, or to get the data via the clearinghouse from the server of a provider.

Further developments of the NCGI are:

• the establishment of a separate foundation NCGI for its development and exploitation in October 1997;
• expenditure of the architecture and the participants to enlarge the applicability of the clearinghouse;
• creation of a search engine for the data in the clearinghouse and the development of free public software for the use of the data in the clearinghouse;

It is important to make distinction between the need of a metadata standard and a standard for finding data (attribute definition for search interoperatibility). The function of a clearinghouse may either be to make data available or provide opportunity the find the data

• using the CEN prEN 12657 standard, the NCGI may become a national node for European geographic information. Main problems in using the standard were the differences in interpretation of the elements of the standard and its complexity. The Netherlands Cadastral Registry developed a simplified version of the model that is applied;
• evaluate the consequences of using shareware and Internet, using a central or decentral concept;
• in the exploitation decisions have to be taken in financial (which is presently cost recovery) and juridical (privacy and protection of confidential information) matters.

The data framework in the CGDI (Canadian Geospatial Data Infrastructure) consist of three layers:

1. underling geodetic control network data to provide the geospatial reference system;
2. core data, which is comprised subset of the National Topographic Database (NTDB) and other selected data from participating federal and provincial agencies. It includes major roads, railroads and intersections, major transportation network, major rivers, the coastline, toponomy (names), administrative boundaries and major elevation data. The core data would be made freely available without copyright restrictions for purpose of promoting the use of one common framework for geographic information. Imagery dataset are included in the clearinghouse at a later stage;
3. basic data including fuller NTDB data, provincial data, thematic datasets as environment, forestry, geology, agriculture, landuse, etc.

Test sets containing a small area of Canada are available to demonstrate and confirm that the system is operational. Harmonisation of data licensing and pricing is developed. Metadata standards are available in the Canadian standard (SAIF) and application programmes are available for accessing the data in different formats.

In April 1994, United States President Clinton issued the Executive Order (number 12906) ”Co-ordinating Geographic Data Acquisition and Access” [Clinton, 1994]. The National Spatial Data Infrastructure. NSDI can be described as the umbrella of policies, practices, standards, organisations and data that contribute to enhanced availability, quality and use of geo-spatial data in the new technological conditions. Under the NSDI various programmes have been initiated as parts of the USA development of Geographic Information Infrastructure:

• National Geographical Data Clearinghouse;
• Geographical data standards;
• Data framework;
• Partnerships.

In the USA many databases with geographical information exists. However they are of different source, captured for a wide variety of applications and with different quality and resolution. Their use is rather mixed by private and public organisations on national, regional and local level. In 1984, the need for a standard spatial transfer format became aware and the FICCDC (Federal Interagency Coordinating Committee on Digital Cartography (predecessor of the present US Federal Geographic Data Committee, FGDC) started the development of SDTS (Spatial Data Transfer Standard) that is used in the National Geographic Data Clearinghouse as stated in the Executive Order 12906.

Section 3 of the Executive Order 12906 for the development of a National Geospatial Data Clearinghouse from the President of the USA ”Standardized Documentation of Data” states: ... each agency shall document all new geospatial data it collects, or produces, either directly or indirectly, using the standard under development by the FGDC, and make that standardized documentation electronically accessible to the Clearinghouse Network. ...”. In addition all other organisation within the USA are invited and encouraged to make geographical data accessible through the Clearinghouse. So, all basic databases within the USA is encouraged to become available through the Clearinghouse. At present the Clearinghouse comprise the geodetic network information, digital ortho-photographs, topographic- height-, (rail-) road-, hydrographic and cadastral data. Users may add thematic data as soil-, vegetation-, geology-, landscape-, population data, etc.

In 1985 the Finish Ministry of Agriculture started a project for mutual use of geo-information by EDI (Electronic Data Interchange) in a Geographic Information Service Centre for providers and users.

The components of this centre (see fig. 1) are the systems of the providers and users, a data network, a directory system, a metadata database all working as one logical system.

The basic idea of the system is that users may request information in a standardised manner and answers are given in ‘real time’. In this way the transfer of whole datasets by the network is avoided because only the data belonging to the answer is transferred by the network.

Request of the end users are converted by the EDI translator for transport to the systems of the providers where the answers are selected and transferred back to the end user. The answers may consist of pieces of data and information from different geographic databases which are part of the system.

Providers have a contract with the centre for update quality, security, copyrights and protection of non-public available data.

Since 1992 producers of GIS have worked together in an Open GIS Consortium to open their data formats and structure on geographic dataset in order to allow the mutual access to either databases.

The concept behind the Open GIS is not to uniform the datastructures and format of each individual manufacturer but leave their own copyright and their developments and allow access to data, stored in either GI-system.

The concept of Open GIS (see fig. 2) enables the user to open a digital gateway to the different types of databases possibly at different locations. These gateways stay open during all the enquiry process to enable interactive access to each of the GIS’s. Within the user’s workstation, the conceptual schemas of the respective GIS’s to be consulted, are available in a computer readable form and used to access the data in the different GIS’s. A standard query language is used to make the queries understandable by each of the different GIS’s.

In this way the data provider can maintain their own databases in their own conceptual data structures, even while the database is queried from outside. Also the user performing the query is guaranteed of the most up to date data present in the database. Using a standard data representation system] and together with the respective standardised conceptual schemas, defined by OGC [1997] the user can also combine data from different sources and type into one representation.

For the development of a national Geographic Information Infrastructure it appears that not only the techniques (communication possibilities) are inevitable but also the standards for unambiguous understanding of the data by the users and the provider as well as a policy on charging services and extension of the types of data that become available in the GII system.

The development of a national GII therefore becomes complicated project. Taking the experience of prior developments in different countries into account a simple start (e.g. as in the Netherlands) enables a swift use of the main functions of the GII. Growing from that model into an more extensive model (e.g. the United States America) is a natural extension. When the development of an interactive GII system (e.g. Finland or the OGC examples) is aimed a complete different approach is required from the beginning.

In the development of a nati0nal GII the use of standards becomes a crucial issue. However the developments of standards diverts in the different international arena’s. The international proposals on metadata and quality standards of CEN and ISO are both sufficiently applicable for this purpose. Choice of one above the other involves also the choice for the type of the other standards because the difference in terminology.

With Europe politically evolving into one market, the possibility of the creation of the national GII system as a national node for the European supra-national GII system will influence the development the national system itself.

1. Aalders, Henri J.G.L. 1996 *
   Standaardisatie, een (internationaal) vereiste, RAVI Jaarboek 1996, Amersfoort (NL)

1. Bogaerts, Theo J.M., Henri J.G.L. Aalders and Jerzy Gazdzicki, 1997 *
   Components of Geo-Information Infrastructure, Proceedings ELIS’97, Prague

1. CEN *
   Geographic Information, Reference Model, ENV 12009, August 1997

1. Geographic Information, Data Description, Spatial schema, ENV 12160, August 1997

1. Geographic Information, Data Description Quality, PrEN 12656, December 1996

1. Geographic Information, Data Description Metadata, PrEN 12657, October 1997

1. Geographic Information, Data Description Transfer, PrEN 12658, December 1996

1. Geographic Information, Referencing, Geographic identifiers, PrEN 12761, December 1996

1. Geographic Information, Referencing, Position, PrEN 12761, December 1996

1. Clinton, William J., 1994 *
   Co-ordinating Geographic Data Acquisition and Access: The National Spatial Data Infrastructure, Executive Order 12906, April 11, 1994

1. FGDC (Federal Geographic Data Committee), 1995
   Content Standard for digital geospatial Metadata, June 8, 1994

1. Workbook for Standards for Digital Geospatial Metadata, c/o USGS, 590 National Centre, Reston VA, March 24, 1995

1. Moellering, H., et al, 1991
   Spatial database transfer standards: current international status, Elsevier Applied Sciences, London (UK)

1. WWW, 1997
   Dublin Core Element Set: Reference description,
   http://purl.org/metadata/dublin_core
   Dublin Core Resource Types,]