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Mount Isa Inlier 1:100 000 geology: lithostratigraphy and chronostratigraphyNote: This metadata describes the dataset in accordance with the ANZLIC (Australia New Zealand Land Information Council) Core Metadata Guidelines Version 2. Dataset citationANZLIC unique identifier: ANZCW0703003759 Title: Mount Isa Inlier 1:100 000 geology: lithostratigraphy and chronostratigraphy CustodianCustodian: Geoscience Australia Jurisdiction: Australia DescriptionAbstract: These data are a digital representation of information depicted on the printed maps of Seigal, Hedleys Creek, Carrara Range Region, Lawn Hill Region, Riversleigh, Constance Range Region, Mount Oxide Region, Mammoth Mines Region, Myally, Alsace, Coolullah, Kennedy Gap, Prospector, Quamby, Mount Isa, Mary Kathleen, Marraba, Cloncurry, Oban, Duchess Region, Malbon, Kuridala Region, Selwyn Region, Dajarra and Ardmore 1:100 000 Geological Series and Mount Drummond 1:250 000 Geological Series produced by AGSO, the Geological Survey of Queensland (GSQ) and Northern Territory Geological Survey (NTGS). 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, era, period 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:
Spatial domain:
Geographic extent polygon: 136.5 -17.5, 141 -17.5, 141 -22, 136.5 -22, 136.5 -17.5,
Data currencyBeginning date: 1990-01-01 Ending date: 2001-06-30 Dataset statusProgress: Complete Maintenance and update frequency: Not Known Access
Access constraints: LIcence required Free Data DownloadData qualityLineage: 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. See "More Metadata" 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 1:25 000 scale, while data were digitised from the standard 1:100 000 geological map. Thus, the total estimated positional error due to map production process is about +/-125 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 colour aerial photographs at 1:25 000 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 such as 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 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
Metadata informationMetadata date: 2013-03-08 Additional metadataMetadata reference XHTML: http://www.ga.gov.au/meta/ANZCW0703003759.html Metadata reference XML: http://www.ga.gov.au/meta/ANZCW0703003759.xml Data are unprojected from Universal Transverse Mercator (UTM) projection into geodetic coordinate system. Australian Geodetic Datum 1966 (AGD66). Spheroid, is the Australian National Thematic coverages were edge-matched with surrounding tiles, where data was available. While, in general, features at the coverage boundaries matched, sometimes it was necessary to carry out some interpretative work. In particular, where the discrepancy between two same arcs features at the adjoining tiles was less than 250 m, the nodes were snapped at half-distance from their original position. Once edge-matched, all of the thematic coverages were appended into a single, seamless thematic coverage. However, boundaries of the individual map tiles were not dissolved. The sets of attributes in the seamless coverages were appended and existing ones modified as per specifications in version 2000.07 of the Geoscience GIS Data Dictionary. A greater part of the work was focussed on attributes for the geology theme. Stratigraphic unit names were validated against records in Geoscience Australia's Stratigraphic Index database. Unitage and agerank attributes were added and populated, with the latest age terminology for each unit. Three more attributes were added to improve the query capability of the data. They are superseq (super sequence), superbasin (super basin) and ign_event (igneous event). The naming of granites and the break up of granite batholiths has been updated, using the most recent scientific information available. For further information see metadata accompanying the GIS data. Authors:Wyborn, L.A.I. Ratajkoski, M. Retter, A.J. Southgate, P.N. Jackson, M.J. Scott, D.L |
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