GEOLOGY:

There are three steps relating to the initial data capture and upgrade to a high-level GIS: (i) Interpretation and creation of source maps; (ii) Data capture from source maps; (iii) Post-data capture upgrade.

(i) Geological maps are a depiction of information acquired from interpretation (mostly aerial photography), field observation, and subsequent investigation (eg sample analysis for age and rock-type determination). Some detail may have been generalised, re-positioned, or omitted from the primary data for cartographic purposes. Maps were compiled from unrectified photo overlays onto topographic bases supplied by the Commonwealth mapping authorities. Drainage and, other topographic features (eg fence lines) were used for spatial control of the geological data.

(ii) Data were captured from stable-base repromat used in the production of the hardcopy multi-colour geological maps. Initial acquisition was by high precision scanning. Resultant raster files were warped to fit digital graticules generated using Intergraph CAM software. Affine-1 warp was used, with the four corners of each tile forming tie points. Warped raster files were then vectorised and cleaned up using Abakos Provec and Scanfix software. Further interactive editing and additional capture of point data was carried out using MicroStation software. MicroStation vector data were plotted and visually checked. MicroStation vector data were translated to ArcInfo coverage format using in-house scripts and ESRIs IGDSARC utility. Attribute fields were populated using information from the printed maps and coverages were built for topology, checked and edited.

(iii) The original data are imported from export files into double precision ArcInfo coverages. Spatial processing and transformations on the data were done using ESRI's ArcInfo (version 7.2.1) GIS software.

ROAD NETWORK (National Geoscience Dataset):

This dataset (ANZCW0703002391) was compiled by Geoscience Australia staff from the original Digital Chart of the World VPF format dataset downloaded from the DCW website listed in the abstract. For information on the lineage of the original DCW (VPF format) datasets please view the Digital Chart of the World website listed in the abstract. The roads dataset was simplified so that only the towns relevant for the Online GIS were present.

Post-DCW lineage

The seperate DCW tiles NA11, UA11, QC32-33, QD31-33, QE31-33, QF31-33 and all the RC, RD, RE, RF, SC, SD, SE, SF, TC, TD, TE, TF, UC, UD, UE, UF, VC, VD, VE, VF, WC, WD, WE, WF, XC, XD, XE, XF, YC, YD, YE, YF, ZC, ZD, ZE and ZF were compiled into single covers based upon the separate DCW themes. The vegetation layer was not available for the Australian area.

The data was then attributed fully as the existing coverages were attributed in code which only made sense with the DCW Data Dictionary. The field names were changed to be clearer for example the field AEPTVAl was changed to Elevation. No cleaning of the data was necessary exept for the place names coverages where upper and mixed case place names existed in the DCW data these were all changed to mixed case.

Geoscience Australia compliant fields were added to the data at this stage: UFI and FEATURE with AGSO_CODE and DESC added to non-polygon themes.

This dataset is a subset of the transport coverage which was compiled from the original DCW railroad arc coverage, the road arc coverages, the transportation structure line coverage, the transportation structure point coverage and the aeronautical point coverage.

POPULATION CENTRES (National Geoscience Dataset):

The population centres dataset (ANZCW0703002389) was simplified so that only the towns relevant for the Online GIS were present.

See "More Metadata"