The National Spatial Strategy

2002 - 2020

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Part 3 Your Responses

7    Data Issues

Data are at the heart of any spatial information system and thus data needs to be a specific and important focus of attention.
From an SDI perspective data may be viewed and categorised in various ways. The importance of whatever categorisation is adopted can not be overemphasised as data policies will be developed on the basis of the data categories which are adopted.
Probably one of the most basic concepts in an SDI is the notion of spatial data(see Part 2, Section 1). Broadly spatial data can be classified as reference data and attribute data. Another approach to categorising spatial data is to distinguish between core data and thematic data. These four categories (reference, attribute, core and thematic data) are not mutually distinct and thus any single data set may fall into more than one of the above four categories. As the categories provide a framework for viewing data matters and shaping policies, it is thus important that further comment is provided regarding the nature of each type of data.

  • Spatial data refers to data which has been linked to a point, area or volume in space. The links (also sometimes referred to colloquially as 'tags') can take a number of forms [1]. The information which is tagged may take any form. In the context of the ISDI, digital data are the type of data which is of greatest interest.
  • Reference data refer to maps or remotely sensed images (air photographs, satellite images) against which other data (e.g. road accidents, location of school pupils, monuments etc) are 'referenced' so as to show geographical position. It is vitally important that such maps or images indicate accurately the spatial location of the objects (roads, houses, trees etc) which they show. Reference data as defined here are normally in raster format, but may also be available in vector format.
  • Attribute data are data which provide additional information about a spatially identified 'object'. For example, a car crash may be represented by a star on a map, in which case the associated attribute data may be the make of car, the time of day of the crash etc. To a large extent the power of GIS systems lies in them being able to quickly and easily access such attribute data. In principle all data can be linked to spatial position and thus all of the data held by organisations can become spatial data, provided it is linked to a spatially defined object. The real benefits of an SDI will emerge as more and more otherwise non-linked data become spatially tagged. Attribute data may be held in tabular, text, image or other formats.
  • Core data are the priority spatial data which in the ISDI should be maintained to the highest standard and be made widely and easily available. Core Data may be reference or attribute data. Some of the kinds of data which could be regarded as Core Data are :-
    (1) Coordinate reference systems
    (2) Base maps
    (3) Remotely sensed rectified images (orthophotographs, satellite images)
    (4) Geographical place names
    (5) Geographical grid systems
    (6) Addresses
    (7) Legal and administrative boundaries
    (8) Transport networks (road, rail, airports, harbours)
    (9) Hydrography including water catchment areas
    (10) Terrestrial elevation
    (11) Bathymetry and coastline
    (12) Oceanic spatial features
    (13) Protected sites
    (14) Land cover
    (15) Cadastral parcels
    (16) Development Plans
    (17) Planning applications
    (18) Selected basic demographic data
    (19) Selected infrastructure (gas, telecommunications, electricity)
    (20) Selected basic enterprise data
    (21) Selected public facilities data (schools, hospitals, Garda stations etc)
    (22) Geological data
  • Thematic data are data in broad fields or areas such as education, health, planning etc. Given the relative lack of resources it is necessary to identify priority thematic areas so that the data in these areas can be adequately spatially referenced, harmonised on a priority basis.

[1] The tags can be:-

  • Through identifying x, y and z co-ordinates which define unique points on the earth
  • In real-time through linking to some positioning system such as GPS (or Galileo in future)
  • Through word linkages (e.g. County Meath)
  • Through alphanumeric 'bar codes' which are unique to defined spatial objects
  • By linking to other 'objects' which are themselves spatially positioned (e.g. a vector boundary data set).


(1)    Does Ireland have adequate types of reference data, and if not what other types should we have?

(2)    What forms of data should be regarded as Core Data?

(3)    What are the priority thematic areas in which special effort should be made to get spatial data properly organised?

(4)    What are the constraints which would limit your organisation adequately organising its data holdings?

(5)    What additional resources would be needed to adequately organise your data?

(6)    What are the priority data in your organisation which should be adequately organised?

(7)    Have you any views on the various forms of spatial referencing?

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