SDI - SPATIAL DATA INSFRASTRUCTURE

The term “Spatial Data Infrastructure” (SDI) is often used to denote the relevant base collection of technologies, policies and institutional arrangements that facilitate the availability of and access to spatial data. The SDI provides a basis for spatial data discovery, evaluation, and application for users and providers within all levels of government, the commercial sector, the non-profit sector, academia and by citizens in general.

The word infrastructure is used to promote the concept of a reliable, supporting environment, analogous to a road or telecommunications network, that, in this case, facilitates the access to geographically-related information using a minimum set of standard practices, protocols, and specifications. The applications that run “on” such an infrastructure are not specified in detail in this page. But, like roads and wires, an SDI facilitates the conveyance of virtually unlimited packages of geographic information. An SDI must be more than a single data set or database; an SDI hosts geographic data and attributes, sufficient documentation (metadata), a means to discover, visualize, and evaluate the data (catalogue and Web mapping), and some method to provide access to the geographic data. Beyond this are additional services or software to support applications of the data. To make an SDI functional, it must also include the organisational agreements needed to coordinate and administer it on a local, regional, national, and or trans-national scale. Although the core SDI concept includes within its scope neither base data collection activities nor myriad applications built upon it, the infrastructure provides the ideal environment to connect applications to data – influencing both data collection and applications construction through minimal appropriate standards and policies.

The creation of specific organisations or programs for developing or overseeing the development of SDI, particularly by government at various scales can be seen as the logical extension of the long practice of co-ordinating the building of other infrastructures necessary for ongoing development, such as transportation or telecommunication networks.

(Source: The SDI Cookbook; www.gsdi.org)

Institutional Framework
Since the whole scope of a SDI is to facilitate better accessibility and exchange of data between different producers and users of spatial data, a well-organised infrastructure for co-ordination and co-operation between different stakeholders is necessary. In fact, this a prerequisite to start an initiative to create a SDI, and is often the first step in the process. The framework is to cover issues like institutional agreements, data sharing policies, data pricing policies, institutional responsibilities, legislation in the area, private integrity policies etc. To manage all issues it is convenient to form some kind of organisational body, having the responsibility to co-ordinate all matters. The members of this body should consist of representatives from all major stakeholders in the GI-community. The role of this body could be from a decision-making authority with mandate to decide upon issues regarding GI, to an advisory board aimed at discussing GI-matters.No matter what kind of body is formed and with what mandate, it is critical to identify the correct level of the representatives from the stakeholders.
In whatever form the framework is established, it is essential for the stakeholders to have clear and unanimous view on the co-operation behind the SDI and the policies creating it.

Technical Standards
Today the general advantages with using standards in different technical fields are fairly understood by most people. Still, when identifying type of standards needed for a facility like a Spatial Data Infrastructure, it is not obvious which kind of standards are appropriate, which standards exist or how to implement them in the SDI. Looking over the whole concept of an SDI gives a variety of standards on different levels covering everything from Cabling and Electrical Interfaces to Map Presentation. In this very first stage of the establishment, it was decided to focus on a few.

Data Format and Exchange

Metadata

Software

International Standardisation Bodies

Fundamental Datasets
At the national level, common spatial data is often defined through community and/or national agreements on content, known as "framework" or "fundamental" data in various national SDIs. A fundamental dataset can be described as a dataset for which several government agencies, regional groups and/or industry groups require a comparable national coverage in order to achieve their corporate objectives and responsibilities. The content of the fundamental datasets varies from SDI to SDI or country to country. There are though a number of geographic data sets that could be considered more or less compulsory, these are

Geodetic reference system

Basic Topographic features (roads, lakes, rivers, cities/villages, land use etc)

Cadastre information (land registry)

Technological Framework
Technological Framework in an SDI refers to all technical facilities needed to support an SDI. It could be the network for transfer of all data, metadata facilities to provide information about the existing data, hardware necessary for the SDI, and so on. The technical solution behind a SDI varies from case to case. In some cases it is convenient to collect all existent data and store it in one centrally managed database, though in other cases it is considered most efficient to let data be at its place of production. Some other solutions also exist in-between these two. As for the Institutional Framework, it could be necessary to form a body with the responsibility to manage all technical issues behind the SDI. This body, compared to the other one, should be more technically oriented and should consist of staff with knowledge in database management, telecommunication, computer networking and other general IT-issues.