Reference data, as defined in the ETeMII White Paper on Reference Data, are those datasets that are needed to integrate and link other data sets and ensure that information is properly related within a spatial context. You can think about reference data as a "skeleton" of Geographic Information applications. The White Paper also identifies the following components of reference data:

• Geodetic reference system (i.e. a co-ordinate system) for both horizontal and vertical measurements.
• Units of administration
• Units of land rights, i.e. cadastral parcels
• Addresses
• Selected topographic themes - notably elevation, transport networks and hydrography, and
• OrthoImagery

There is no internationally agreed definition for these terms. They all have similar ideas behind them, but differ slightly according to the context in which they are used - particularly in regard to the legal and commercial issues that surround them. Hence care should be taken when using the terms. Some of the better known contexts are given below:

• The US NSDI adopted the term core data to define data used by most and shared by everyone, maintained in a common standard (framework data form this core). (http://www.fgdc.gov/framework/frameworkintroguide/chapter3.html).
• In the Canadian Geospatial Data Infrastructure (CGDI), the term framework data is used to describe the set of continuous and fully integrated geospatial data that gives context and reference information for the country. (http://cgdi.gc.ca/english/rfp/announcements/RFP_SD_definition.pdf)
• In South Africa framework data aims to provide a reliable, standardised source for commonly needed and used geo-spatial data themes. By attaching their own geographic data - which can cover innumerable subjects and themes - to the common data in the framework, users can build their applications more easily and at less cost. (http://www.nsif.org.za/Framework/fdv_metadata.html)
• In the Australian Spatial Data Infrastructure a fundamental dataset is a dataset for which more than one government agency requires consistent national coverage in order to achieve their objectives. (http://www.anzlic.org.au/asdi)
• The term fundamental data is also used by the Permanent Committee on Geographic Information Systems Infrastructure for Asia and the Pacific. (http://www.gsi.go.jp/PCGIAP/)

As can be seen in the answer to the question "What is Reference Data", the term is more than just topography - although it does include some important topographic components (elevation, transport networks and hydrography).

One of the basic ideas behind Reference Data is that they already exist in some form within each country - although there is no consistency in these components across Europe (at this point time). Examples of national initiatives to create reference data include:

A useful starting point for finding different Reference Data components the National Mapping Agencies within each country. Information on the different agencies can be found on the EuroGeographics website (http://www.EuroGeographics.org) under the About Us section. Information about different products can be found in the GDDD section.

The main advantage of having everyone use the same information relates to the

• Ability to easily exchange information between applications, and the
• Savings on cost that comes from removing duplication of effort in collecting and manipulating information.

Many projects spend considerable time and efforts looking for suitable reference data (or even producing or updating it) to the detriment of data analysis or the production of new thematic information. The use of reference data is a way to optimize our activities and this becomes indispensable with the greater use of the web.

Most of the reference data are produced by Public Authorities (e.g. National Mapping Agencies, Cadastres, Statistical Offices). There are, however, some examples of reference data, e.g., ortho-imagery, that can be provided by any number of organisations - public or private.

Certification of geo-spatial data is not really diffused until now. A ISO standard for GI quality assessment is under preparation (ISO/DIS 19114) but it will take time to introduce ISO 9000 certification as common practice.

In some cases there is a duplication in data collection due to overlapping of the geographic extent of responsibility between different organisations (i.e. in transboundary regions) or due to separate collections at different level (local, regional, national). One of the aims in developing national or European reference data is to avoid this as it uses valuable time and money - not only for creation but also for the consequences on updating and maintenance.

NMAs are just one of the different groups that can be suppliers of reference data. In many countries, data such as cadastre, addresses, ortho-imagery are not produced by the National Mapping Agencies. For some components the private sector is also to be considered as a important provider.

This depends on the national situation. In some cases this work will done in response to market demands whilst in others, the priorities for activities (including maintenance) will be set internally within the organisation.

The answer to these three questions depends on the situation within the country concerned - and the organisation that is supplying the reference data component. For most organisations, some for of cost recovery operates - whether wholly or partially. So typically there are significant costs associated with the creation and maintenance of reference data. (Just look at the annual budget for National Mapping Agencies and the National Cadastral Organisations). These costs are met by those people who use the data - at least in part.

There have been some efforts to create Reference Data components within Europe by EuroGeographics - notably:

• Administrative boundaries (within the SABE product),
• PETIT/EuroRegionalMap (1:250,000 scale topographic product), and
• MapBSR/EuroGlobalMap (1:1,000,000 scale topographic product).

Other initiatives come from the private sector through organisations such as TeleAtlas and Navtech.

As indicated above, a useful starting point for finding different Reference Data components the National Mapping Agencies within each country. Information on the different agencies can be found on the EuroGeographics website (http://www.EuroGeographics.org) under the About Us section. Information about different products can be found in the GDDD section.

There are some initiatives to provide Reference Data over the web. A good example is the work associated with the Digital National Framework (DNF) in the UK which is aiming to make the different components of reference data supplied by the National Mapping Agency (Ordnance Survey) available in new ways (http://www.ordsvy.gov.uk/dnf/).