Data Quality

Positional Accuracy

Positional accuracy is an assessment of the closeness of the location of the spatial objects in relation to their true positions on the earth’s surface. Positional accuracy consists of 2 assessments:

  • Horizontal accuracy assessment, and

  • Vertical accuracy assessment.

The horizontal and vertical positional accuracy is the assessed accuracy after all transformations have been carried out.

Coordinates Referencing the GDA2020 Datum

Spatial features referencing the GDA2020 datum are produced using a coordinate transformation from the GDA94 datum using the following parameters.

  • shift_x = 0.06155,

  • shift_y = -0.01087,

  • shift_z = -0.04019,

  • rotate_x = -0.0394924,

  • rotate_y = -0.0327221,

  • rotate_z = -0.0328979,

  • scale_adjust = -0.009994

Attribute accuracy

Attribute accuracy is an assessment of the reliability of values assigned to features in the dataset in relation to their true ‘real world’ values.

Key attributes (name and the unique identifier) have a high degree of accuracy in the order of 99.09%. Other attributes derived from the processing of supplied data may have a lower degree of accuracy but less than previously released data. All attribute accuracies are dependent on the data accuracy supplied to Geoscape Australia.

For this product, feature and attribute accuracy is a measure of the degree to which the features and attribute values of spatial objects agree with the information on the source material. The allowable error in attribute accuracy was previously up to 5%.

A precise attribute accuracy assessment may not always be possible. In these cases an intuitive estimate of the expected attribute accuracy or the likely maximum error based on previous experience is acceptable.

Logical Consistency

Logical consistency is a measure of the degree to which data complies with the technical specification. The allowable error in logical consistency previously ranged from 3% to 5%. The test procedures are a mixture of software scripts and onscreen, visual checks. The data structure has been tested for conformance with the data model. The following have been tested and confirmed to conform:

  • File names

  • Attribute names

  • Attribute lengths

  • Attribute types

  • Attribute domains

  • Attribute order in file

  • Object type

  • Compulsory attributes populated

Topological Consistency

Topological consistency is the measure of how features spatially relate to other features within and across themes. Topological inconsistencies are identified using a combination of automated rules and visual analysis. Where topological inconsistencies are identified they are notified back to the supplier organisation for remediation at the source. Some minor topological inconsistencies are corrected during product processing using automated rules. The level of topological consistency is dependent on the data supplied to Geoscape.

Electoral Boundaries has been processed to assure all polygons are stored as single part features to improve compatibility with a range of software applications. Due to this there can be a duplication of PIDs (e.g. STATE_ELECTORAL_PID) within a layer (e.g. State Electoral Boundaries) where there are multiple polygons represented by a single PID.


Completeness is an assessment of the extent and range of the dataset in regard to completeness of coverage, completeness of classification and completeness of verification.

Attribute completeness

All attributes for each object are populated according to the data model, noting that some attributes are not mandatory.

Temporal accuracy for each layer is applicable to its most current release.

Quality scope

Polygon geometry accuracy and attribute accuracy for all included areas.