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The Real World: The real world is where customers and
users operate, it is where they have their problems and
require solutions to those problems. Unfortunately for the
digital cartographer the real world does not stop at the
doors of the shopping mall, or as one disappears under a
railway bridge. The real world is also three dimensional
incorporating underground objects and those in which we
which live and work on a daily basis.
2. NATIONAL GEOSPATIAL DATABASE
2.1 The concept
The concept of a British National Geospatial Database
(NGD) was announced in late 1995 (Nanson et al 1995)
and has received a positive response from all areas of the
geospatial data community: The aim of the NGD is to
establish an infrastructure to promote and gain maximum
benefit from datasets, principally those held by
Government Departments, Executive Agencies and Local
Authorities. Some of this data is already accessible while
other datasets are not. They all have one attribute in
common - they have some form of geospatial reference -
ie. the data has a geographic coordinate or has an
indirect geographic reference - through, for example, a
postal address.
The benefits of data integration at the local level in a GIS
are well known for a wide variety of planning aspects,
infrastructure development, environmental protection etc.
Considered at a national level there are benefits for
citizens, government and businesses to be derived from
the value adding services that can exploit a geospatial
data infrastructure. The full potential benefit can clearly
be significantly more productive than simply the sum of
the individual data themes.
The NGD is not the sole preserve of Ordnance Survey
and will require the development of a collaborative
framework to establish, support, promote and develop the
concept and its benefits. For the NGD to be successful,
partnerships will be essential to direct, fund, motivate and
realise the concept. Similar initiatives are emerging
elsewhere, an early pioneer was the National Spatial
Data Infrastructure (NSDI) in the United States (US
Government 1995).
There are differences between the USA and Great Britain
that mean that the NSDI would not export directly to Great
Britain. These include factors that are cultural and legal
(for example in the attitude to government information)
and organisational (for example in the way in which in
Britain government departments can - and do - compete).
Equally in other countries there is a history of
rationalisation of geography so that, for example, in
France the départments and subdivisions form not only
administrative but also postal, utility and other
geographical units. This does not happen in Britain
where as an example postal ‘counties’ do not exist
administratively.
101
What therefore needs to be done to achieve the NGD
vision in Great Britain ?
2.2 Standards:
Standards are necessary to provide access to data and to
integrate data. For example, a land registration body will
hold a unique reference number against a land parcel, the
local authority will also hold data about that property - but
each will have developed their own unique reference
system over the years. The British Standard 7666 has
been developed to support the creation of Land and
Property, Street and Rights of Way Gazetteers through
the assignment of unique reference identifiers. The
gazetteer acts as a link between disparate datasets.
This is just one example, there are other standards issues
which must be addressed if reliable conclusions are to be
made from integrating two or more datasets.
2.3 Coordinate
transformations
reference systems and
Great Britain, like many countries has a well defined
geodetic framework that dates from the 1930s. This is the
base on which all the mapping has been created. New
locational systems such as GPS give users much more
ability to locate themselves absolutely and demonstrate
the of the map framework.
Given three datasets each with coordinate resolutions to,
say, 0.1 m. The combination of those datasets would not
be non trivial if they had been based on different
coordinate reference systems, for example, the British
National Grid, ETRF89 (European Terrestrial Reference
Framework 1989 used for GPS) and a local council plane
grid. Proven and reliable transformation parameters are
essential to merge the datasets with any confidence
(ignoring the fact at this stage that the overhead of doing
SO over a wide area network within a geospatial query
could be prohibitively expensive in terms of processing
power).
There is a vast amount of data, referenced to old
mapping that would be uneconomic, even with today's
technology, to make compatible it with other data.
2.4 Data - populating the NGD
Currently no one knows just what geospatial information
exists, how much of it is in digital form and to what extent
it follows recognised standards. OS operates the SINES
(Spatial INformation Enquiry Service) database on behalf
of central government. SINES is a meta-database
containing descriptions of nearly 600 geospatially
referenced datasets. SINES is accessible on the OS
website (address below). It is envisaged therefore that
datasets will be gradually added to the NGD provided
they meet certain criteria and as data providers wish to
collaborate.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996
