Advanced Search  |  
 

NTData (digital geology of the Northern Territory)

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: ANZCW0703002369

Title: NTData (digital geology of the Northern Territory)


Custodian

Custodian: Geoscience Australia

Jurisdiction: Australia


Description

Abstract:

These data are a digital representation of information depicted on printed maps from the

Australia 1:250 000 Geological Series produced by AGSO and the Northern Territory Geological

Survey (NTGS) between 1963 and 1997. The data are in a tiled format and are not seamless,

although basic edgematching has been done where possible. Tiles are arranged according to the

standard Australian 1:250 000 sheet breakup. The complete dataset will be comprised of the 90

tiles covering the Northern Territory; a one tile verge all around may be added in the future.

Data present include geological polygons (stratigraphic units), linear structural features (faults,

dykes, folds, trends, lineaments etc), and point features (dips, mines, age localities etc).

Polygons have a range of attributes extracted from each individual map including unit name, age

and lithology, 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 descriptions is available.

NTData has gradually evolved from elementary CAD quality data into its present topologically

structured GIS format, and hence has many imperfections and inconsistencies. The spatial

accuracy of data from some older maps is particularly problematical. Data has undergone only

moderate checking due to limited resources. See ADDITIONAL METADATA.

ANZLIC search words:

  • GEOSCIENCES Geology Mapping
  • GEOSCIENCES Geology Maps

Spatial domain:

locality map

Geographic extent polygon: 129 -11, 138 -11, 138 -26, 129 -26, 129 -11,

Geographic bounding box:
North bounding latitude: -11 °
South bounding latitude: -26 °
East bounding longitude: 138 °
West bounding longitude: 129 °

Data currency

Beginning date: Not Known

Ending date: Not Known


Dataset status

Progress: In Progress

Maintenance and update frequency: Not Known


Access

Stored data format:
DIGITAL - dgn MicroStation Design Graphic Network (DGN) MicroStation Universal Transverse Mercator (UTM) AGD66
DIGITAL - ArcGIS-coverage ArcInfo coverage Universal Transverse Mercator (UTM) AGD66
Available format type:
DIGITAL - dgn MicroStation Design Graphic Network (DGN) MicroStation Universal Transverse Mercator (UTM) AGD66
DIGITAL - e00 ArcInfo export (e00) ArcInfo Workstation Universal Transverse Mercator (UTM) AGD66
DIGITAL - dat Data file MapInfo Universal Transverse Mercator (UTM) AGD66

Access constraints:

Licence and fee required.

Order Product

Data quality

Lineage:

Source maps: the geological maps are a depiction of information acquired from interpretation (mostly airphoto), field observation, and subsequent investigation (eg sample analysis for age and rock-type determination). Some detail may have been generalised, repositioned, or omitted from the primary data for cartographic purposes. Maps were compiled from unrectified photo overlays onto topographic bases supplied by Australian Government mapping authorities. Drainage and, where necessary, other topographic features (eg fence lines) were used for spatial control of the geological data (see POSITIONAL ACCURACY).

NTData: 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 (via data heads-up digitising over the warped raster images) was carried out using MicroStation (V4.4.023) software. Data on some tiles were block shifted to account for datum/spheroid changes (See ADDITONAL METADATA for more information). MicroStation vector data were plotted and visually checked prior to conversion to GIS format. No attribution was attached to the MicroStation data.

MicroStation vector data were translated to Arc/Info coverage format using in-house scripts and ESRIs IGDSARC utility. Attribute fields were populated using information from the printed maps and coverages were built, checked and edited. Arc/Info coverages were then written as both double and single precision uncompressed Arc Export format.Arc Export files were translated into MapInfo tables using MapInfo Professional (V4.02) and ArcLink (V3.1.2).

Positional accuracy:

An accurate assessment of horizontal accuracy is not possible because the history of the original source information and subsequent revisions by the States is not fully known. However during construction of the dataset we observed a range of errors/anomalies which we believe may be due to: (i) inaccurate topographic bases, (ii) spheroid/datum differences, (iii) map production processes.

Attribute accuracy:

Attributes are mostly a representation of information on the source maps and should be viewed in that context - some of the information/interpretation is more than 35 years old and may be incorrect/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 kowledge/information available at the time of production of the source map.

General: geological units and linear structures such as faults and folds were largely interpreted from airphotos in conjunction with field observation/measurement, and sample collection and analysis. The reliability diagram on the printed geological source maps gives 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 interpretations.

Point data attributes, eg strike and dip values, 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 facsimile of the primary data).

Logical Consistency:

Data have been checked visually on plots and for topological consistency using in-house routines and Arc/Info GIS software. 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 NTData, not all attributes are complete for all elements or tiles. In some cases (eg the age, name and genealogy of stratigraphic units), information may be outdated and may also be inconsistent between tiles. The latest information is often available in various AGSO databases, eg the Stratigraphic Names database, but this has not been incorporated into NTData tiles at this time.

Classification: completeness and consistency of classification needs to be considered in the context of the time span of the source geological maps (1963-1997) 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 etc (accurate, approximate, concealed, inferred) for example is not particularly consistent and therefore needs to be treated with caution. Additionally, maps produced since the early 1980s will have been subject to more field checking, and may have had the advantage of remotely sensed data (Landsat and geophysical images). In general, one can say that modern maps (and hence the digital data derived therefrom) contain significantly more detail (are less generalised and have greater subdivision of geological units) than older maps.

Verification: there is no consistent record of the extent of field observation as opposed to remote (airphoto) interpretation. However the frequency of measured sites on maps, eg dips of bedding etc, is a reasonable indicator of field activity/verification. More information can be found in Explanatory Notes which were produced in conjunction with the geological maps.


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/ANZCW0703002369.html

Metadata reference XML: http://www.ga.gov.au/meta/ANZCW0703002369.xml

Stirzaker, J., 1996. NTData. Technical papers of the Mapping Sciences 96 Conference. Mapping Sciences Institute, Australia, Canberra, 1996, 249-258.

Authors:Stirzaker, J.
SPATIAL INFORMATION FOR THE NATION