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Geology of the Cape Van Diemen

Note: This metadata describes the dataset in accordance with the ANZLIC (Australia New Zealand Land Information Council) Core Metadata Guidelines Version 2.


Dataset citation

ANZLIC unique identifier: ANZCW0703003151

Title: Geology of the Cape Van Diemen


Custodian

Custodian: Geoscience Australia

Jurisdiction: Australia


Description

Abstract:

These data are a digital representation of information depicted on the printed map of the Cape Van Dieman 1:250 000 Geological Series produced by AGSO and the Geological Survey of Queensland (GSQ) in 1979.

Data present include geological polygons (litho-stratigraphic units), linear structural features (faults, dykes, folds, trends, lineaments etc), and point features (mines, structural points etc). Polygons have a range of attributes extracted from each individual map including unit name, age and lithological description, while lines and points are feature coded according to the AGSO publication 'Symbols Used On Geological Maps' (BMR 1989). A standard look-up table of AGSO geological codes and associated descriptions is available (see ADDITIONAL METADATA).

The data has gradually evolved from elementary CAD quality data into its present topologically structured GIS format, and hence has many imperfections and inconsistencies. Data has undergone rigorous validation and testing that includes over 80 different tests. See ADDITIONAL METADATA for more information on the data standards used.

ANZLIC search words:

  • GEOSCIENCES Geology Mapping
  • GEOSCIENCES Geology Maps

Spatial domain:

locality map

Geographic extent polygon: 139.5 -16, 141 -16, 141 -17, 139.5 -17, 139.5 -16,

Geographic bounding box:
North bounding latitude: -16 °
South bounding latitude: -17 °
East bounding longitude: 141 °
West bounding longitude: 139.5 °

Data currency

Beginning date: 1979-01-01

Ending date: Not Known


Dataset status

Progress: Complete

Maintenance and update frequency: Not Known


Access

Stored data format:
DIGITAL - ArcGIS-coverage ArcInfo coverage Geographic GDA94
Available format type:
DIGITAL - dat Data file MapInfo Geographic GDA94
DIGITAL - shp ArcView shape file ArcView Geographic GDA94

Access constraints:

Licence required.

Free Data Download

Data quality

Lineage:

Source: The geological maps are a depiction of information acquired from interpretation, field observation, and subsequent investigation. 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 were used for spatial control of the geological data.

Data capture: 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. Affine-1 warp was used, with the four corners of each tile forming tie points. Warped raster files were vectorised and cleaned, followed by interactive editing and additional capture of point data (via data heads-up digitising). Vector data were plotted and visually checked prior to conversion to GIS format. Translation from MicroStation to ArcInfo format was facilitated using in-house scripts and IGDSARC utility. Attribute fields were populated using information from the printed maps. Coverages were built for topology, checked and edited.

Upgrade: Data are unprojected from UTM projection into geodetic coordinate system. In addition, a datum-shift was performed from AGD66 to GDA94. Coverages were edge-matched with the surrounding tiles, where data was available. While, in general, features at the coverage boundaries matched, sometimes it was necessary to carry out limited interpretative work. Attributes were appended and existing modified as per specifications in the AGSO GIS Data Dictionary. Stratigraphic unit names were validated against records in AGSO's Stratigraphic Index database. Where superseded, they were replaced with the current names. Additional attributes, from the database, were added to all geological units with a known stratigraphic unit name.

Positional accuracy:

An accurate assessment of horizontal accuracy is not possible because the history of the original source information and subsequent revisions are not fully known. However a range of errors and/or anomalies were observed during construction of the dataset. These are possibly due to: (i) inaccurate topographic bases; (ii) spheroid or datum differences; and (iii) map production processes.

The error associated with delineation of geographic features and map production process is estimated at 0.5 mm at the respective map scale. Geological interpretation from the aerial photography was carried out at 1:85 000 scale, while data were digitised from the standard 1:250 000 geological map. Thus, the total estimated positional error due to map production process is about +/-170 m. However, positional accuracy for some of the edge-matched features at the tile boundary is estimated to be up to +/-300 m. This estimate should be interpreted in conjunction with the positional accuracy of the topographic base used in the interpretation of source data.

Attribute accuracy:

Attributes are mostly a representation of information on the source maps and should be viewed in that context - some of the information and/or interpretation is more than 20 years old and may be incorrect and/or outdated. Attributes are tile specific - for example the same geological unit on separate tiles may have different lithological descriptions, ages and possibly even names. This is a reflection of the knowledge and/or information available at the time of production of the source map.

Geological units and linear structures such as faults and folds were largely interpreted from black and white aerial photographs at 1:85 000 scale. The interpretation was carried out in conjunction with numerous field observations and/or measurements, and sample collection and analysis. The reliability and field site location diagrams on the printed geological source maps provide some (basic) indication of the level of work undertaken. Most of the source maps have accompanying Explanatory Notes, which provide much more detail about the geology and interpretative work.

Point data attributes have been extracted from the map and thus may include cartographic generalisation and error (maps were however subject to considerable checking and editing during their production, and can be considered a good representation of the primary data).

Logical Consistency:

Data have been checked visually on plots and for topological consistency using in-house routines and ArcInfo GIS software. In addition, the upgrade of the data required passing on a number of rigorous validation tests. As much as possible, every effort has been made to ensure that the accuracy and standards of the source maps have been maintained.

Completeness:

Coverage: Because the geological maps are the only source for the data, not all attributes are complete for all elements or tiles. In some cases, for example the age, name and genealogy of stratigraphic units, information may be inconsistent between tiles.

Classification: Completeness and consistency of classification needs to be considered in the context of the time span of the source geological map and the highly interpretative nature of the discipline. Broadly similar classification and measurement techniques have been applied to geological map compilation for many years, however resultant data does reflect individual geologists ideas and preferences. The classification of boundaries, faults and similar features (ranging from accurate, approximate, concealed, inferred) for example is not particularly consistent and therefore needs to be treated with caution.

Verification: There is no consistent record of the extent of field observation as opposed to airphoto interpretation. However the frequency of measured sites on maps, such as measurements of mesoscopic structures, is a reasonable indicator of field activity and/or verification. More information can be found in Explanatory Notes, which were produced in conjunction with the geological map.


Contact information

Contact organisation: Commonwealth of Australia (Geoscience Australia) (GA)
Contact position: Manager Client Services
Mail address: Cnr Jerrabomberra Ave and Hindmarsh Dr
Mail address: GPO Box 378
Locality: Canberra
State: ACT
Country: Australia
Postcode: 2601
Telephone: 02 6249 9966
Facsimile: 02 6249 9960
Electronic mail address: sales@ga.gov.au

Metadata information

Metadata date: 2013-03-08


Additional metadata

Metadata reference XHTML: http://www.ga.gov.au/meta/ANZCW0703003151.html

Metadata reference XML: http://www.ga.gov.au/meta/ANZCW0703003151.xml

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Authors:Grimes, K.
SPATIAL INFORMATION FOR THE NATION