PRINCIPLES OF THE ASGC
The ASGC is constructed on the principle that it must fulfil user needs for spatial statistics while also conforming to general classification principles.
The ASGC is constructed on the basic classification principles that members within one class are of the same type, classes are uniquely defined so as to be mutually exclusive and, in total, the members in each class cover the entire class.
As a result, the geographical units of each hierarchical level in each classification structure of the ASGC are:
- of the same type, delimited by well-defined criteria
- clearly demarcated by precise boundaries
- uniquely identified by codes and names
- mutually exclusive
- in aggregate cover the whole area to which that hierarchy applies.
The ASGC is designed to meet user needs for social, demographic and economic statistics. The smallest units of the ASGC i.e. CDs at census times and SLAs at intercensal times, have been designed such that they are:
- convenient and efficient for data collection
- useful and relevant for data dissemination
- flexible for aggregation to larger units
- useful building blocks for user-defined regions.
Thus, CDs are designed for efficient data collection at census times. Each CD covers an area which allows census data to be collected in an efficient and cost effective manner. SLAs are defined on the administrative areas of local governments. Local governments are both a useful source of data and a relevant dissemination unit for users.
CDs aggregate to SLAs which, in turn, aggregate to other larger areas of the ASGC. Each of these geographical areas serves a specific purpose and meets user needs. Many organisations employ the CDs and the SLAs as the building blocks to construct their own geography for statistical purposes.