GEOGRAPHIC INFORMATION INFRASTRUCTURE AND ITS STANDARDISATION
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
SUMMARY
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.
INTRODUCTION
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.
Level |
Name |
Involves |
1 2 3 4 5
6
7 |
Physical Data link Network Transport Session
Presentation
Application |
physical properties of the link properties of the transmission medium communication network protocols ensuring of error-free interchange control structure with dialogue discipline and protocol recovery application protocols e.g. compression or encryption services as FTP or e-mail |
Table 1. The ISO communication layer structure |
CONCEPTS FOR GII
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:
STANDARDS
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):
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:
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).
Fig. 1 Mutual relation between the standardisation of data and processes.
Standards for processes encompass standards for data capture, analysis and representation of geographic data standards. The development of standard functionality in Geo-IT leads to standard interpretable applications that can be used in comparing different results of analysis. Implicitly it also aims at better knowledge transfer and mutual understanding of Geo-IT applications.
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.
INTRODUCTION OF STANDARDS
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:
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.
INTERNATIONAL DEVELOPMENTS ON STANDARDS
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:
Institute |
Standard name |
Remarks |
CEN/TC 287 (Comité Européen de Normalization) |
CEN 12... |
In development since 1992. |
ISO/TC 211 (International Standardisation Organisation) |
- |
TC founded in April 1994. First design for work programme ready. |
IHO (International Hydrographic Organisation) |
S 57 (DX 90) |
Only for hydrographic mapping
|
CERCO (Comité Européen des Responsables de la Cartographie Officielle) |
ETDB (European Territorial Data Base) |
Development within the MEGRIN project group to link existing and future national data. |
DGWIG (Digital Geographic Information Working Group) |
DIGEST (DIgital Geographic Exchange Standard) |
Transfer between national systems and development of an integrated NATO- structure. |
Drive EDRM/ CEN/TC 278 |
GDF 2.0 (Geographic Data File) |
Developed for transport and road telematics. Prenorm from March 1996. |
Table 2. Existing international standard(-commission)s for the transfer of geographic data. [Moellering, 1991]
EXAMPLES OF GII’s
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:
GII in the Netherlands:
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:
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
GII in Canada
The data framework in the CGDI (Canadian Geospatial Data Infrastructure) consist of three layers:
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.
GII in the USA
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:
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.
GII in Finland
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.
Open GIS
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.
CONCLUSIONS
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.
REFERENCES
http://sunsite.berkely.edu/Metadata/structuralist.html