Australia: Our national stories
Australian Heritage Commission, 2003
ISBN 0 642 23561 9
2. Principles of the New Methodology (continued)
2.4 The Computing Environment
The Commission primarily operates the NWI on SUN workstations, running SUNOS 4.1.3. Data entry and editing work has been undertaken on a Sun workstation and an IBM compatible personal computer.
The host Geographic Information System (GIS) for the NWI is ARC/INFO version 6 (ESRI Pty Ltd). All data entry, storage, manipulation and analysis for the NWI was carried out using this software. The ARC/INFO software uses a number of conventions for describing the data and associated files it uses which are followed in this handbook.
Digital data sets of information are referred to as coverages. In a coverage, map features are stored as simple points, lines, or polygons. A coverage contains both locational data (which defines points, lines, and polygons) and attribute data (which describes points, lines, and polygons) about each feature. Descriptive data are stored in attribute tables as items related to each feature type. The manager of this attribute information is INFO.
These tables are referenced by coverage name then attribute table name; for example,'lattice'.PAT refers to the coverage lattice and PAT refers to it¼s associated attribute table. Additional attribute information is stored for wilderness survey coverages in other attribute tables. The most important of these, described further in Section 4, is the BIO table associated with each lattice coverage.
The NWI makes use of the Librarian module in ARC/INFO to manage most of the primary data. Librarian is built upon the idea of partitioning and distributing a spatial data set. It partitions data in two ways: by tile and by layer. A tile is a single partition and for the NWI corresponds to a 1:250Ý000 survey unit framework (shown in Figure 3.1).
A layer generally comprises one coverage type; for example, all roads. Each type of primary data is stored separately in the tiled library structure as a data layer. Primary data obtained at differing scales and spatial extents are stored and managed together within the single tile/layer framework of Librarian. Analysis in the NWI is undertaken through the use of programs written using the ARC Macro Language (AML) of ARC/INFO. AML provides full programming capabilities and a set of tools to tailor the user interface of the NWI application.
The NWI makes use of the ability of AML to automate the frequently performed actions undertaken in the analysis process. It is the tool used to ensure the consistency and repeatability of analysis results.