The full power of GIS systems can be harnessed when data are coded in terms of xy (and z) co-ordinates. Spatially 'tagging' data in this way can indicate positions at very high levels of accuracy. High level of spatial accuracy are very useful for most purposes and there is little doubt that where possible this form of spatial tagging should be undertaken when data are being collected. However two basic problems may exist if data were to be provided (outputted) only in xy(z) format.
Firstly, tagging in this way means that in the case of some types of data (e.g. census information, household surveys), the privacy of data suppliers (individuals, households, businesses, organisations) can be compromised.
Secondly, many data users would not have access to software which can manipulate data which are in xy(z) format.
In order to get round these difficulties it would be necessary before outputting data to aggregate the information. This would ensure that individual records can not be identified. It would also make it possible for standard widely used software programmes (e.g. Excel) to store and manipulate the output data.
From the ISDI perspective, the questions become :-
- is it possible and appropriate to identify a network of areas across the whole State which would be the smallest spatial units ('atomic' areas) for the supply of certain kinds of data?
- In the case of data which do not have potential privacy difficulties, what types of data should be made available (outputted) in terms of areas rather than in xy(z) terms?
From an analytical point of view the smaller the extent of the atomic areas the better. Having established such a small area network other data which are not tagged in terms of xy(z) co-ordinates could be tagged using these atomic areas.
Having established such a network of smallest areas, it is desirable that whenever larger areas are used to collect or display data, these larger areas are whole multiples of the atomic areas (i.e. the larger areas do not involve splitting any of the atomic areas). For many purposes a basic hierarchy of areas along the lines set out below may be appropriate.
- Atomic areas at the bottom of the spatial hierarchy
- Electoral Divisions
- Local authority areas
- The State
- The island of Ireland
Obviously this basic hierarchy would not be suitable for all purposes (e.g. analysing water quality by water catchment) and data providers would need to shape their data output areas to suit their user needs. However where possible and appropriate data providers would be encouraged to issue data in terms of these areas or in a form which would enable the data to be aggregated or disaggregated into these basic types of areas without the necessity to split atomic areas.