Section 1 - National Topographic Database Structure and Specifications

1. Scope of this document

This Section of the Technical Specifications clarifies the aspects of the feature based model used for the National Topographic Database (NTDB). It provides information on a variety of topics relating to the model design and population principals including:

  • defining planimetric and altimetric accuracies
  • clarifying feature content, topological structure requirements and feature level metadata
  • defining datum, spatial extents and projection information, as well as
  • the rules used in the collection and attribution of the data.
This feature based model is used for the capture, revision and maintenance of topographic data and is used as a basis in the production of series and customised mapping. The key characteristics required of this feature based model is national consistency and assured quality.

The NTDB is managed by the Oracle Relational Database Management System (RDBMS) and ESRI's ArcSDE software; it contains all the relevant data tables and indexes. Revision, capture and maintenance of these databases may occur either in an ESRI ArcSDE versioned environment or via independent geodatabases detached from the SDE environment.

The 1:25 000 National Topographic Information Coordination Initiative (NTICI) data capture program will be conducted via preliminary file geodatabases detached from the SDE Environment. The 1:25 000 NTICI data capture program is being conducted in concert with state and other federal government agencies with a focus on information required for emergency response purposes and the capture of detailed hydrology information. This work is constantly evolving as requirements change.

The NTDB will be utilised by Geoscience Australia to capture, store and maintain features in their best possible positional accuracy and delineation. The data stored in the NTDB will then be utilised to generate products at various scales. This data will also be utilised by government as well as industry for modelling, strategic planning and information exchange.

The NTDB baseline data used to populate the model initially was the Series 3 TOPO250K GEODATA vector product, a nationally consistent product covering the entire country at a minimum of 1:250 000 suitability. This baseline data has since been progressively updated with information derived from the NTICI program as well as detailed theme revision and pinpointed maintenance based on infrastructure growth and decline.

2. The NTDB Model

2.1 The Feature-Based Data Model

The NTDB is a feature-based data model. The following definitions describe the components of this feature-based data model:

ENTITY:

An entity is a real world phenomenon not divisible into phenomena of the same kind.

FEATURE INSTANCE:

A feature instance is an abstraction of an entity represented in digital form. The description of a feature instance encompasses only selected properties of that entity. Feature instances can also be referred to as features.

FEATURE SUBTYPE:

A specific property of a feature instance within a Feature Type and its associated Feature Class requiring discrimination.

FEATURE TYPE:

A subset of coded feature instances within a Feature Class that identify the type of topographic feature being represented, sharing common geometry and specific like characteristics.

FEATURE CLASS:

A collection of Feature Types with unique properties and behaviour, sharing the same type of geometry i.e. point, line or polygon.

FEATURE DATASET:

A collection of Feature Classes that share topological relationships.

ATTRIBUTE:

An attribute is a particular property of a feature or of a feature's property. Attributes can be spatial (or locational) and aspatial (or non-locational).

ATTRIBUTE VALUE:

Attribute value is the value assigned to an attribute, either for a feature instance or its attributes.

ENTITY CLASS:

A group of entities of the same kind, matching the members of a feature class.

The structure of a feature instance in the feature based data model can be summarised as:
feature instance = [ spatial object + attribute object ]

Where spatial object and attribute object are defined as:

SPATIAL OBJECT: The addition of all the locational attributes of the feature instance in the form of geometrical objects such as points, lines or polygons. Spatial objects carry a spatial address that consists of one or more couplets (x, y) or triplets (x, y and z) of coordinates. In the feature-based data model, topological relationships will be carried as part of the spatial object whenever the transfer formats support them. Real- world features are modelled in the NTDB using Points, Lines and Polygons. Multi–Polygons can also exist but do not occur within the NTDB. These types of spatial objects are described below:


Spatial Object Table
Point  
Geometric representation defined by a single 'x, y' co-ordinate couplet or an 'x, y, z' triplet. Three special points are used in the data model.  
Entity Point - used to locate point features or area features represented by a point. Point Symbol
Node - A point that is an intersection of two or more chains or an end point of a chain. Node Symbol
Vertex - A point that is a change of direction along the length of a chain. Vertex Symbol
Line  
A sequence of non-intersecting line segments bounded by nodes (not necessarily distinct) at each end.
Chains will reference their start and end nodes. Coordinates along a chain are referred to as vertices in this specification.
Line Symbol
Polygon  

A defined continuous region consisting of an interior area and zero or more nested defined holes (voids). In this specification, dependant on scale, inner and outer boundaries may also defined by sets of chains.

Within a feature class the polygons are mutually exclusive.

Multi-polygons are two or more polygons, not abutting each other, treated as a single feature. No Multi-polygon features should exist within the NTDB.

Polygon Symbol

ATTRIBUTE OBJECT: The non-locational information about a feature instance. This data identifies the Feature Type as well as the aspatial attributes of a specific instance of the Feature Type. The attribute object is composed of one or more attributes.


Attribute Object Table : Example 1
Spatial Object Attribute Object
Chain (x1,y1 .....xn,yn) Attribute Attribute Value
Feature Type: Road
Name: PIONEER HIGHWAY
Classification: Principal Road
Formation: Under Construction
National Route Number: A42
State Route Number: 37
Feature Reliability: 16/10/2002
Feature Source: GEOSCIENCE AUSTRALIA
Attribute Reliability: 22/08/2002
Attribute Source: GEOSCIENCE AUSTRALIA
Planimetric Accuracy: 100
Revised: 22/04/2003
Text Note: position approximate
Symbol250K: 252

Attribute Object Table : Example 2
Spatial Object Attribute Object
Polygon Attribute Attribute Value
Feature Type: Marine Swamp
Type 2
Name:  
Feature Reliability: 14/10/2002
Feature Source: GEOSCIENCE AUSTRALIA
Attribute Reliability: 14/10/2002
Attribute Source: GEOSCIENCE AUSTRALIA
Planimetric Accuracy: 9999
Revised: 22/05/2002
Text Note:  
Symbol100K: 908

2.2 Data Aggregation

The spatial object and attribute object as defined above are the primitive components of data. These data objects are grouped together in a hierarchy which is used for the capture, manipulation and transfer of the data.

2.2.1 Feature Datasets

The digital spatial data contained in the NTDB is primarily derived from a combination of existing map production material, base digital data, imagery and authorised reference and supporting material. This data may be divided into themes, each theme containing logically related geographic information. On entry to the NTDB features are grouped under Feature Datasets which bring together those features sharing a close topological relationship and common "theme" i.e. features are broadly categorised according to their physical or cultural similarities.

There are twenty three different Feature Datasets used within the NTDB. The feature datasets are:

  • Administration
  • Aviation
  • Bathymetry
  • Cartography
  • Culture
  • Drainage
  • Errors
  • Framework
  • FrameworkMIL
  • Habitation
  • Industry
  • Marine
  • MetadataIndex
  • Physiography
  • Production
  • RailTransport
  • Relief
  • RoadTransport
  • SpatialIndex
  • SurveyMarks
  • Utility
  • Vegetation
  • Waterbodies

2.2.2 Feature Classes

All NTDB vector data is topologically structured and this is reflected in the way the data is released to the public. Feature classes are composed of different spatial objects and convey the topological relationships of the data. There are two hundred and thirty feature classes in the NTDB. Each feature class contains numerous aspatial attribute fields which may be required by users to populate.

The NTDB may contain four types of feature classes:

  • Annotation
  • Linear
  • Polygon
  • Point

Annotation feature classes contain blob elements representing textual information required for map face production purposes.

Linear feature classes contain chain features representing entities such as windbreaks or pipelines.

Polygon feature classes contain areas (which may be bounded by linear feature classes) representing features such as lakes or built-up areas.

Point feature classes contain point features representing entities such as buildings or lighthouses.

2.2.3 Non Spatial Tables and Relationship Classes

The NTDB contains thirteen additional tables outside of the feature classes. These tables can be accessed independently from the features classes, when required, however some have been designed to be revised in concert with defined feature classes within the data model. These tables provide the ability to store multiple records of non spatial (or aspatial) information related to a single spatial object.

For more information on the structure of the Non Spatial Tables and associated relationship classes see Section 3 4.4 Non Spatial Tables and Relationship Classes.

3. Data Capture Accuracy, Integrity and Extent

The NTDB vector data is topologically structured with fully maintained complex inter-relationships. Additional metadata about the capture of features in the NTDB is conveyed by attributes held at the feature level as well as within two metadata indexes and their related tables.

During capture/maintenance processes the topologically structure is revised with selective inter-relationships maintained when both features forming the inter-relationship are captured/maintained at the same time. Additional information about features is held by either:

  • two metadata indexes and their related tables, or
  • at the feature level, dependant on the type of feature being captured/revised and/or the requirements of the Geoscience Australia Stakeholders with vested interest in the capture.
The inter-relationships with features not participating in a capture/maintenance process are then reviewed as well as metadata transfer requirements dealt with by Geoscience Australia prior to finalisation.

3.1 Datum, Projection and Co-ordinate Extents

The datum used in the NTDB is GDA94, and the coordinate system is geographicals i.e. latitudes and longitudes.

While the spatial domain is larger, the designated extent of the NTDB is 0 to -48 degrees of latitude and 96 to 168 degrees of longitude. The extent takes into account Lord Howe Island, Norfolk Island, Christmas Island and Cocos Islands. Only features within these limits will be acceptable.

The spatial indexes for each feature class have been customized for the greatest efficiency at a national scale in the maintenance of the NTDB. The only exception is Annotation feature classes which have a single spatial index of 1000.


FeatureDataset FeatureClassName GeometryType Grid 1 Grid 2
Administration AdministrationAreas Polygon 1.5  
Administration InternationalBoundaries Polyline 5  
Aviation AircraftFacilityAreas Polygon 0.1  
Aviation AircraftFacilityLines Polyline 0.1  
Aviation AircraftFacilityPoints Point 5  
Aviation AirportAreas Polygon 0.1  
Aviation NavigationAids Point 0.5  
Aviation NavigationLights Point 0.5  
Bathymetry BathymetricAreas10MIL Polygon 5  
Bathymetry BathymetricAreas2_5MIL Polygon 5  
Bathymetry BathymetricAreasWAC Polygon 5  
Bathymetry Isobaths10MIL Polyline 5  
Bathymetry Isobaths2_5MIL Polyline 5  
Bathymetry IsobathsWAC Polyline 5  
Cartography CartographicLines Polyline 5  
Cartography CartographicPoints Point 0.25  
Cartography Graticules100K Polyline 5  
Cartography Graticules10MIL Polyline 5  
Cartography Graticules2_5MIL Polyline 5  
Cartography Graticules250K Polyline 5  
Cartography Graticules5MIL Polyline 5  
Cartography GraticulesWAC Polyline 5  
Cartography Grids100K Polyline 5  
Cartography Grids250K Polyline 5  
Culture AerialCableways Polyline 0.1  
Culture CemeteryAreas Polygon 0.1  
Culture CemeteryPoints Point 1.5  
Culture DamWalls Polyline 0.1  
Culture EmergencyFacilityPoints Point 0.5  
Culture Fences Polyline 0.25 1
Culture LandmarkAreas Polygon 0.5  
Culture LandmarkPoints Point 0.5  
Culture RecreationAreas Polygon 0.1  
Culture TouristPoints Point 0.5  
Culture VerticalObstructions Point 0.5  
Culture WasteManagementAreas Polygon 0.5  
Culture WasteManagementPoints Point 0.5  
Culture Windpumps Point 0.5  
Culture Yards Point 0.5  
Drainage CanalLines Polyline 0.25  
Drainage Locks Point 0.5  
Drainage RapidLines Polyline 0.1  
Drainage Spillways Polyline 0.1  
Drainage WatercourseLines Polyline 0.1 0.5
Drainage WaterfallPoints Point 0.5  
Errors Errors Point 0.5  
Framework FrameworkBoundaries Polyline 5  
Framework Islands Polygon 1  
Framework LargeAreaFeatures Polygon 5  
Framework Locations Point 0.25  
Framework Mainlands Polygon 5  
Framework Seas Polygon 5  
FrameworkMIL FrameworkBoundaries10MIL Polyline 5  
FrameworkMIL FrameworkBoundaries2_5MIL Polyline 5  
FrameworkMIL FrameworkBoundaries5MIL Polyline 5  
FrameworkMIL FrameworkBoundariesWAC Polyline 5  
FrameworkMIL Islands10MIL Polygon 1.5  
FrameworkMIL Islands2_5MIL Polygon 1  
FrameworkMIL Islands5MIL Polygon 1  
FrameworkMIL IslandsWAC Polygon 1.5  
FrameworkMIL Mainlands10MIL Polygon 5  
FrameworkMIL Mainlands2_5MIL Polygon 5  
FrameworkMIL Mainlands5MIL Polygon 5  
FrameworkMIL MainlandsWAC Polygon 5  
FrameworkMIL Seas10MIL Polygon 3  
FrameworkMIL Seas2_5MIL Polygon 3  
FrameworkMIL Seas5MIL Polygon 3  
FrameworkMIL SeasWAC Polygon 3  
Habitation BuildingAreas Polygon 0.1  
Habitation BuildingPoints Point 0.1  
Habitation BuiltUpAreas Polygon 0.5  
Habitation PopulatedPlaces Point 1.5  
Industry Conveyors Polyline 0.5  
Industry MineAreas Polygon 0.1  
Industry MinePoints Point 0.5  
Industry PetroleumWells Point 1  
Industry StorageTanks Point 3  
Marine ForeshoreFlats Polygon 0.25  
Marine MarineHazardAreas Polygon 0.25  
Marine MarineHazardPoints Point 1  
Marine MarineInfrastructureLines Polyline 0.1  
Marine MarineInfrastructurePoints Point 3  
Marine ReefLines Polyline 0.5  
MetadataIndex FieldInspectionIndex Polygon 5  
MetadataIndex WorkPackageIndex Polygon 5  
Physiography Caves Point 1.5  
Physiography Craters Polygon 0.1  
Physiography DeformationAreas Polygon 0.5  
Physiography Discontinuities Polyline 0.1  
Physiography Pinnacles Point 3  
Physiography SandRidges Polyline 0.1 0.5
Physiography Sands Polygon 0.25  
Production ProductionIndexes Polygon 3  
Production ProductionNotePoints Point 3  
RailTransport RailwayCrossingLines Polyline 0.1  
RailTransport RailwayCrossingPoints Point 1.5  
RailTransport Railways Polyline 3  
RailTransport RailwayStopPoints Point 1  
Relief Contours100K Polyline 0.5 3
Relief Contours10MIL Polyline 1 5
Relief Contours2_5MIL Polyline 5  
Relief Contours250K Polyline 1 5
Relief Contours5MIL Polyline 5  
Relief ContoursWAC Polyline 1 5
Relief HypsometricAreas10MIL Polygon 1.5  
Relief HypsometricAreas2_5MIL Polygon 5  
Relief HypsometricAreas250K Polygon 1.5 5
Relief HypsometricAreas5MIL Polygon 5  
Relief HypsometricAreasWAC Polygon 1.5  
Relief SpotElevations Point 0.25  
RoadTransport FerryRouteLines Polyline 5  
RoadTransport FootBridges Polyline 0.5  
RoadTransport FootTracks Polyline 0.5  
RoadTransport RoadCrossingLines Polyline 0.1  
RoadTransport RoadCrossingPoints Point 1  
RoadTransport Roads Polyline 0.25 1.5
RoadTransport TrafficControlDevices Point 3  
SpatialIndex GeodataIndexes250K Polygon 3  
SpatialIndex MapIndexes100K Polygon 3  
SpatialIndex MapIndexes2_5MIL Polygon 3  
SpatialIndex MapIndexes250K Polygon 3  
SpatialIndex MapIndexesWAC Polygon 3  
SpatialIndex SettlementDensityBoundaries Polyline 5  
SpatialIndex SettlementDensityIndex Polygon 5  
SurveyMarks BenchMarks Point 0.5  
SurveyMarks HorizontalControlPoints Point 0.5  
Utility LiquidFuelDepotPoints Point 1  
Utility LiquidFuelRefineryPoints Point 1  
Utility LiquidFuelTerminalPoints Point 1  
Utility PetrolStationPoints Point 1  
Utility Pipelines Polyline 5  
Utility PowerlineDistributionNetwork Polyline 0.25 1
Utility PowerlineTransmissionNetwork Polyline 0.25 1
Utility PowerStations Point 5  
Utility SewageTreatmentPlants Point 5  
Utility SubStations Point 1  
Utility TelephoneExchanges Point 1  
Vegetation ClearedLines Polyline 0.5  
Vegetation CultivatedAreas Polygon 0.25  
Vegetation NativeVegetationAreas Polygon 0.25 3
Vegetation Seagrass Polygon 3  
Vegetation Windbreaks Polyline 0.1  
Waterbodies Bores Point 0.5  
Waterbodies CanalAreas Polygon 0.1  
Waterbodies Flats Polygon 0.25 3
Waterbodies Lakes Polygon 0.1 1
Waterbodies PondageAreas Polygon 0.1  
Waterbodies RapidAreas Polygon 0.1  
Waterbodies Reservoirs Polygon 0.25 1
Waterbodies Springs Point 1.5  
Waterbodies WatercourseAreas Polygon 0.5  
Waterbodies Waterholes Point 0.5  
Waterbodies WaterPoints Point 0.5  
Waterbodies WaterStoragePoints Point 0.25  

3.2 Data Projection and Editing

It is important to note that in most cases (i.e. when carrying out spatial data adjustments), it will be necessary to project "on-the fly" the GDA94 Geographical data to GDA94 UTM (MGA) coordinates when editing, in order to ascertain and comply with the correct linear length and polygon area requirements of the Specification. It is essential that when such projection and editing is conducted, it is performed with respect to the correct UTM zone eg. where a linear feature requires spatial editing and that linear feature straddles two UTM zones, for example zones 52 and 53, it is essential that the projection takes into account where the feature crosses the zone limit otherwise spatial distortion can occur.

3.3 Precision, Resolution and Tolerance

The NTDB will be held in High (Double) Precision. This means each integer coordinate is stored using 53 bits rather than the 31 bits used Low (Single) Precision databases.

The XY Resolution is defined as the number of decimal places or significant digits used to store feature coordinates (in both the x and y direction). The NTDB will have a defined XY Resolution of '0.0000005' degrees, which equates to approximately 0.05 metres on the ground.

The XY Tolerance is minimum distance between two coordinate sets, under which they are considered equal. The NTDB will have a defined XY Tolerance of '0.000001' degrees, which equates to approximately 0.1 metres on the ground.

The spatial domain is defined by a combination of the XY Resolution and the XY Coordinate System. The Spatial Domain determines the extent of the data and is described in coordinate system units.

In the NTDB the Spatial Domain is set as:

Minimum X: -400
Minimum Y: -400
Maximum X: 4503599227.37049
Maximum Y: 4503599227.37049

The coordinate resolution of all features in the source geodatabase supplied for production purposes should be maintained i.e. coordinates will not be rounded in the supplied geodatabase or following subsequent feature editing. (Note: The previous GEODATA requirement to round coordinates does not apply to the NTDB geodatabase model.)


3.4 Point Density Reduction

Point density is controlled so that the locational information is conveyed by the minimum number of points while still retaining the smooth shape of the source information. Increasing the number of points delineating a shape without greatly improving its positional accuracy or shape definition increases data storage requirements and severely inhibits the speed of data processing. In certain cases, such as Limit of Data features, a minimum density is required to ensure positional accuracy in a geographic representation for a feature captured in a projected MGA UTM environment.

The following specifications apply for data point reduction for features captured/revised during NTDB maintenance (including NTICI work packages):

  1. Where Geoscience Australia has supplied base material/digital data derived from a Geoscience Australia Stakeholder (e.g. State, Federal or Local Government Agency) the point density of existing features should not be altered unless the feature is undergoing spatial adjustment to imagery/aerial photography or unless requested to do so by Geoscience Australia. Where a feature is being altered it must conform to Geoscience Australia data point reduction requirements (see details set out in point 4) unless it has to meet a unique instruction set out within the project instructions of the work package.
  2. Where Geoscience Australia has supplied base material/digital data which is unstructured (e.g. contours which have only undergone raster to vector conversion with no topological structuring and/or attribution) it must conform to the point reduction requirements set out in point 4
  3. Where Geoscience Australia has supplied base material/digital data in which it is indicated that the features should not be spatially modified unless undergoing revision (against imagery/aerial photography or another reference source to meet planimetric accuracy requirements), then the point density of existing unrevised features should not be altered. Existing features held within the NTDB would fall into this category as they have already been tested and met acceptable levels. The features undergoing spatial adjustment for revision purposes must conform to Geoscience Australia data point reduction requirements as detailed in point 4.
  4. For features newly captured or subsequently revised during NTDB maintenance, the acceptable minimum length for all line segments will be equal to, or greater than, 0.000 10 degrees (approx. 10m). This minimum segment length rule also applies to Polygon edges.
    However three exceptions will apply and in each case only the minimum number of additional segments needed to conform to planimetric accuracy requirements will be acceptable (ie vertex 'streaming' practices, where vertices are added at regular intervals along a digitized line is not acceptable). These exceptions are:
    • feature instances of less than 20 points (vertices) as these are generally small complex shapes
    • feature instances which require some shorter segments to conform to the planimetric accuracy requirements.
    • Sections of chain which must be coincident with the two feature instances describe above

In addition the following rules apply for data point density regardless of NTDB pre-existing data or Geoscience Australia Stakeholder agreements:

  • For Limit of Data features in all applicable layers the distance between vertices will not exceed 0.002 degrees (approx. 200m).
  • The length of a line segment will not be greater than 0.147 degrees (approx 8000m) for the NTDB. This maximum segment length rule also applies to Polygon edges.

3.5 Global Identifier Attribute and Identification of Change

The NTDB will use a Global Identifier (GlobalID) attribute to identify individual features inside the database. This GlobalID will be unique on a national basis and is expected, in conjunction with a field named Revised to maintain a currency status of edits in the database during its formation and maintenance.

The GlobalID will be assigned to each feature as the database is populated. The GlobalID will be maintained by the database functionality and will remain stable during the majority of attribute and spatial adjustments to a feature. The GlobalID will consist of 36 characters enclosed in curly brackets (eg '{EB07A3A0-A7C3-4A84-AA29-BCE26FDA6838}'). Users of the database should not attempt to alter the entries within this field.

The NTDB will not undergo 'Incremental Update' in the short term. However it will use a field named 'Revised' to provide information on the date a feature was loaded into the database. When a feature is altered in any manner this 'Revised' field will be updated automatically to the date when that change occurred. The 'Revised' date will have no relation to the date on which the feature physically came into existence or was physically altered.

The combination of GlobalID and Revised fields will be unique within the NTDB and will be system generated. Therefore, at this stage, producers are not required to populate these items. In addition producers should not actively modify these fields as this would cause difficulties with the automated processes.

3.6 Feature Metadata

Information on the definition and use of fields detailing feature metadata can be obtained in Section 1 Chapter 3.6.1 "Feature Metadata Fields".

The NTDB captures/stores metadata in two ways:

  • At a feature level; as well as
  • Via a Metadata Index Feature class and an associated table named "FeatureClassesRevised".

The primary method stores metadata at a feature level. This means the metadata about a feature's spatial and aspatial accuracy as well as reliability and source are held against its row record in the associated feature class attribute table. Apart from the standard system generated attribute fields, the following fields will always apply for each feature, at the feature level:

  • Feature Reliability
  • Feature Source
  • Attribute Reliability
  • Attribute Source
  • Planimetric Accuracy
  • Elevation Accuracy (when feature has a height association)
The exception will be features within the Administration (limited feature classes), Cartography, Errors, Production and Spatial Index Feature Datasets.

The Secondary method used for bulk capture/revision processes is to store feature metadata via a Metadata Index feature class named "WorkPackageIndex" and an associated table named "FeatureClassesRevised". This method defines a polygon within the Metadata Index feature class which represents an area where data has been captured, or revised, using a consistent process. Information about the processes and sources used for the revision of data within the area are held with the Metadata Index feature Class. The defined polygon is provided with a unique code which relates to row records within the associated table. A row record in the associated table exists for each feature class which has been revised and defines the metadata about the processes resultant spatial and aspatial accuracy as well as reliability for that feature class. The following Metadata fields are used within the associated table:

  • Feature Reliability
  • Attribute Reliability
  • Planimetric Accuracy
  • Elevation Accuracy (which is populated only when feature has a height association)

Once bulk capture/maintenance processes have been completed the Metadata Index feature class and associated table will be utilised to populate the feature level metadata as the data is reintegrated into the NTDB. The Metadata Index will then be retained within Geoscience Australia for future reference.

NOTE: Geoscience Australia via project instructions to the producers will provide direction on which of the above methods are to be used for a specific work package. Where no direction is provided Feature Level Metadata should be applied.

3.6.1 Feature Metadata Fields

A standard set of fields exist which define the metadata of a feature and their use should meet the definition and required content as set out below.

FIELD FIELD DEFINITION AND REQUIRED CONTENT
Feature Reliability This is the date of the latest primary source material where the position of a particular feature was added, verified, or subsequently changed. When an existing feature is investigated, a new date will be applied once its position and/or existence are confirmed, regardless of whether the feature needed editing on inspection to meet its positional accuracy requirements.

If the latest primary source material for feature positioning (e.g. Imagery/Aerial Photography) is of an older reliability date than that currently populated in the relevant reliability field within the existing base digital data, an Action Request should be sent to Geoscience Australia requesting direction on how to proceed when no relevant information has been supplied in the project instructions.(e.g. When revising the NTDB, a feature contained within the database has a feature reliability of 2005 but the imagery supplied for revising that data has a reliability date of 2003. In this case, an Action Request should be supplied to Geoscience Australia.)

Geoscience Australia will supply information related to Reliability dates for source material as part of "Appendix 1: Source Look-up Table" of the project instructions unless the information is readily available in the metadata of that material.

The Feature Reliability field is a date field which should be stored in the standard Australian format DD/MM/YYYY (e.g. 24/10/1999).
Feature Source This is the name of the latest primary source used to add, update or verify a feature existence or position. Feature Source and Feature Reliability are inter-linked. The date of the latest primary source, used to add, update or verify a feature existence or position, will also be the date used to complete the feature reliability field entry for that feature.

The Feature Source field is a textual field.

The attributes for the FEATURESOURCE items to be assigned for each Feature Type will be determined for each project by Geoscience Australia and supplied to producers as either:
  • A part of "Appendix 1: Source Look-up Table" of the project instructions; or
  • As a populated metadataindex covering the work package.

Attribute reliability This is the date of the latest primary source material used to initially assign, or subsequently change or confirm the value of, one of the attributes of the feature.

If the latest primary source material for attribution (e.g. An Enroute Supplement) is of an older reliability date than that currently populated in the relevant reliability field within the existing base digital data, an Action Request should be sent to Geoscience Australia requesting direction on how to proceed when no relevant information has been supplied in the project instructions.(e.g. When revising the NTDB, a Runway feature contained within the database has a attribute reliability of 2007 but the Enroute Supplement supplied for revising that data has a reliability (issue) date of 2006. In this case, an Action Request should be supplied to Geoscience Australia.)

Geoscience Australia will supply information related to Reliability dates for source material as part of "Appendix 1: Source Look-up Table" of the project instructions unless the information is readily available in the metadata of that material.

The Feature Reliability field is a date field which should be stored in the standard Australian format DD/MM/YYYY (e.g. 24/10/1999).

Additional information on the population of the Attribute Reliability field exist in Section 1 Chapter 3.6.2 "Attribute Reliability and Attribute Source")
Attribute Source This is the name of the latest primary source material used to populate the attribute field/s of a feature.

The Attribute Source field is a textual field.

The attributes for the ATTRIBUTESOURCE items to be assigned for each Feature Type will be determined for each project by Geoscience Australia and supplied to producers as either:
  • A part of "Appendix 1: Source Look-up Table" of the project instructions, or
  • As a populated metadataindex covering the work package

Additional information on the population of the Attribute Source field exist in Section 1 Chapter 3.6.2 "Attribute Reliability and Attribute Source")
Elevation Accuracy This is the standard deviation in metres of the feature's elevation attribute value. Values to be assigned for the elevation accuracy item should preferably be assigned at constant metre intervals (e.g. 5, 10, 15) where possible, with provision for smaller intervals in the higher accuracy values (e.g. 1,2,5) etc.

An entity must be captured at minimum acceptable accuracy for the data quality of a specific model revision process/capture scale. An entity can be captured with higher precision than the stated minimum elevation accuracy. It is unacceptable to capture a feature at a lesser accuracy than stated minimum elevation accuracy and this will be tested for as part of Validation and Testing processes. For a list of minimum acceptable accuracies see Section 1 Chapter 3.7 "Positional Accuracy").

The values for ELEVATIONACCURACY items may be determined for each project by Geoscience Australia (via a mathematical calculation using the variables of inherent error in positional source information, errors inherent in capture and requested accuracy levels supplied to producers). If this occurs it will be supplied to producers as either:
  • A part of "Appendix 1: Source Look-up Table" of the project instructions, or
  • As a populated metadataindex covering the work package
If Geoscience Australia do not specifically provide the values for the Elevation Accuracy item the value:
  • will either be documented in the supplied source material, or
  • the producers should populate the field with a value derived from the information supplied in Section 1 Chapter 3.7 "Positional Accuracy" and the quality of data capture of the feature. If this is the case, producers should supply documentation on what assumptions, if any, were made and the amounts used in the determination of the accuracy value

This item is an integer field and only applies to those features with an elevation attribute.

Additional information on the population of the Elevation Accuracy field exists in Section 1 Chapter 3.7 "Positional Accuracy")
Planimetric Accuracy This is the standard deviation in metres of the position of the feature's horizontal coordinates. Values to be assigned for the planimetric accuracy item should preferably be assigned at constant metre intervals (e.g. 5, 10, 15) where possible, with provision for smaller intervals in the higher accuracy values (e.g. 1,2,5) etc.

An entity must be captured at minimum acceptable accuracy for the data quality of a specific revision process/capture scale. An entity can be captured with higher precision than the stated minimum planimetric accuracy. It is unacceptable to capture a feature at a lesser accuracy than stated minimum planimetric accuracy and this will be tested for as part of Validation and Testing processes. For a list of minimum acceptable accuracies see Section 1 Chapter 3.7 "Positional Accuracy").

The values for PLANIMETRICACCURACY items may be determined for each project by Geoscience Australia (via a mathematical calculation using the variables of inherent error in positional source information, errors inherent in capture and requested accuracy levels supplied to producers). If this occurs it will be supplied to producers as either:
  • A part of "Appendix 1: Source Look-up Table" of the project instructions, or
  • As a populated metadataindex covering the work package
If Geoscience Australia do not specifically provide the values for the Planimetric Accuracy item the value:
  • will either be documented in the supplied source material, or
  • the producers should populate the field with a value derived from the information supplied in Section 1 Chapter 3.7 "Positional Accuracy" and the quality of data capture of the feature. If this is the case, producers should supply documentation on what assumptions, if any, were made and the amounts used in the determination of the accuracy value

This item is an integer field.

Additional information on the population of the Planimetric Accuracy field exists in Section 1 Chapter 3.7 "Positional Accuracy")

3.6.2 Attribute Reliability and Attribute Source

The attribute reliability date and attribute source fields will only be updated if one, or more, of the attributes listed in the table below are added, revised or confirmed. When an existing feature is investigated, a new attribute date and source will be applied once one or more of its attribute/s from the list below are confirmed, regardless of whether the feature needed its attributes updated on inspection.

For example:

  • If the name of a feature is added, revised or confirmed, then the attribute source and attribute reliability fields will be updated because the name field is contained in the list below.
  • If only the symbol250K value for a feature is added, revised or confirmed, then the attribute source and attribute reliability fields will not be updated because the symbol250K field is not contained in the list below.

The attribute reliability date and attribute source are inter-linked. The date of the primary source, used to update the attribute/s from the table below, will be the date used to complete the attribute reliability field entry for that feature.

If more than one source is used to update or confirm a features attributes then the most recent source is used to populate both the 'Attribute Source' and the 'Attribute Reliability' fields. The only exception to this rule is when two, or more of, the sources used have reliability dates within a year of each other. In this case the source used to populate the 'Attribute Source' and 'Attribute Reliability' fields will be that used to populate the item of the highest priority in the table (1 being the highest priority and 101 being the lowest)

For example:

  • A towers name is updated using a tourist information booklet with a reliability date of 01/06/2006
  • The same tower has its height updated using a field revision which took place on 12/05/2006
  • Even though the tourist information booklet is the most recent date, because both sources occur within a year of each other and the height item is considered of higher priority or significance, it is the field revision that is used to populate both the 'Attribute Source' and 'Attribute Reliability' field.

Where a reliability date for a particular source is incomplete (eg has the month and year but no day or the year but no day or month), than it should have the earliest date.

For example:

  • If the source states its reliability as 'May 2006' than the 'Attribute Reliability' field should be populated with '01/05/2006'
  • If the source states its reliability as '2006' than the 'Attribute Reliability' field should be populated with '01/01/2006'

Note: Updating of the 'Attribute Reliability' and 'Attribute Source' fields associated with modifications to the TextNote field will only occur when the altered content is not generic information derived from the definition of the FeatureType or other fields within the record.

For example:

  • The addition of a "Building Point' textnote of 'Satellite Tracking Station' would warrant an update of the Attribute Reliability and Source fields.
  • Where as the addition of a 'Canal Line' textnote 'Drain' would not require an update of these fields.

ITEM PRIORITY ITEM ITEM NAME
1 FEATURETYPE FEATURE TYPE
2 TYPE SUBTYPE NUMBER
2 TYPE_DESCRIPTION DESCRIPTION OF SUBTYPE
3 IUCN IUCN CODING SYSTEM
4 DESCRIPTION DESCRIPTION
5 TOURISTTYPE TOURIST INFORMATION TYPE
6 BUILDINGFUNCTION BUILDING FUNCTION
7 HEIGHT HEIGHT
8 AVERAGEHEIGHT AVERAGE HEIGHT
9 GNAFID GNAF Persistent ID
10 NAME NAME
11 ADMINNAME ADMINISTRATION NAME
12 ROUTENAME ROUTE NAME
13 TRACKNAME TRACK NAME
14 COUNTRYNAME1 COUNTRY NAME 1
15 COUNTRYNAME2 COUNTRY NAME 2
16 SIGNIFICANCE SIGNIFICANCE
17 SECTIONNAME SECTION NAME
18 FACILITIES FACILITIES
19 ALTERNATENAME ALTERNATE NAME
20 POPULATION POPULATION
21 STATUS STATUS
22 RAILSTATIONSTATUS RAILWAY STATION STATUS
23 BUILDINGSTATUS BUILDING STATUS
24 AIRPORTDESIGNATION AIRPORTDESIGNATION
25 SURFACE SURFACE
26 LANDINGACCESS LANDING ACCESS
27 USAGES USAGES
28 CAPACITYKV CAPACITY IN KILOVOLTS
29 FUNCTION FUNCTIONAL ROAD CLASSIFICATION
30 CLASS CLASSIFICATION
31 PASSENGERCAPACITY PASSENGER CAPACITY NUMBER
32 VEHICLECAPACITY VEHICLE CAPACITY NUMBER
33 ELEVATION ELEVATION
34 ELEVATIONFT ELEVATION IN FEET
35 LIGHTING LIGHTING
36 MAST MAST
37 LIGHTFUNCTION LIGHT FUNCTION
38 LIGHTTYPE LIGHT TYPE
39 COLOUR COLOUR
40 DURATION DURATION
41 FLASHES FLASHES
42 GROUPSINGLE SINGLE OR GROUP OBSTACLE
43 STATIONTYPE STATION TYPE
44 TRACKS TRACKS
45 AUTHORITY CONTROLLING AUTHORITY
46 IDCODE IDENTIFICATION CODE
47 FORMATION FORMATION
48 ROADSTATUS OPERATIONAL STATUS OF ROAD
49 GAUGE GAUGE
50 ESA EXCHANGE SERVICE AREA CODE
51 OWNER OWNER
52 PERENNIALITY PERENNIALITY
53 PRODUCT PRODUCT CODE
54 CODE CODE
55 HIERARCHY HIERARCHY
56 OTHERWATERNAME OTHER WATER NAME
57 RELATIONSHIP RELATIONSHIP
58 SYSTEM SYSTEM
59 TEXTNOTE TEXT NOTE
60 NRN NATIONAL ROUTE NUMBER
61 SRN STATE ROUTE NUMBER
62 TRAFFICABILITY LIMITATION TO TRAFFIC ACCESS
63 FLOODLIMITMETRES FLOOD LIMIT IN METRES
64 WEIGHTLIMITTONNES WEIGHT LIMIT IN TONNES
65 HEIGHTLIMITMETRES HEIGHT LIMIT IN METRES
66 SEANAME SEA NAME
67 OCEANNAME OCEAN NAME
68 BEACON BEACON
69 ORDEROFACCURACY HORIZONTAL ORDER
70 ORIGIN ORIGIN
71 STATE STATE/TERRITORY
72 COVERDENSITY FOLIAGE COVER DENSITY
73 ICAODESIGNATION ICAO DESIGNATION
74 FUELTYPE FUEL TYPE
75 CAPACITYMW CAPACITY IN MEGAWATTS
76 GENERATIONMW PLATE GENERATION IN MEGAWATTS
77 VOLTAGEKV VOLTAGE IN KILOVOLTS
78 GENERATIONTYPE POWER GENERATION TYPE
79 GENERATORNUMBER NUMBER OF GENERATORS
80 OPERATOR OPERATOR
81 REPROCESSING REPROCESSING STATION STATUS
82 LANDFILL LANDFILL STATUS
83 TRANSFERSTATION WASTE TRANSFER STATION STATUS
84 YEARCOMMISSIONED YEAR FACILITY COMMISSIONED
85 OPERATIONALUNITS NUMBER OF OPERATIONAL UNITS
86 VOLUMEMEGAL VOLUME IN MEGA LITRES
87 COOLINGTOWERNUMBER NUMBER OF COOLING TOWERS
88 EMISSIONTOWERNUMBER NUMBER OF EMISSION TOWERS
89 CURRENCY CURRENCY DATE
90 PROCLAIMED PROCLAIMED DATE
91 RAAFIDENTIFIER RAAF UNIQUE IDENTIFIER
92 FEATAREA FEATURE AREA
93 LATEST_GAZ LATEST GAZETTEER ENTRY
94 PROVIDER PROVIDER
95 PURPOSE PURPOSE
96 USERACCESS ROAD USER ACCESS
97 TRAVELDIRECTION DIRECTION OF TRAVEL
98 NUMBEROFLANES NUMBER OF LANES
99 SPEEDLIMITKM SPEED LIMIT FOR ROAD SECTION
100 CROSSINGSTRUCTURE CROSSING STRUCTURE
101 MAINTAINER MAINTENANCE AUTHORITY

3.7 Positional Accuracy

The positional accuracy of spatial data is a statistical estimate of the degree to which planimetric coordinates and elevations of features replicate the location of the real world phenomenon that they represent. The positional accuracy is estimated by modelling the propagation of errors in the data production process or by directly comparing the coordinate locations in the completed data against a source of significantly higher known accuracy. Geoscience Australia models their positional and vertical accuracy based on a Gaussian (Normal) distribution and a one-dimensional (linear) method.

For a linear distribution, the standard deviation is computed by squaring all the residual errors, adding the squared values, dividing by the numbers of errors (less one), and taking the square root:

Linear Standard Deviation

In a Gaussian (Normal) distribution, 68.27% of the features would be within 1 standard deviation. The following conversion factors can be used to determine the percentage of features which fall with a multiple of the standard deviation.

From \ To 50% 68.27% 90% 99.73%
50% 1.0 1.4826 2.4387 4.4475
68.27% 0.6745 1.0 1.6449 3.000
90% 0.4101 0.6080 1.0 1.8239
99.73% 0.2248 0.3333 0.5483 1.0



Gaussian (Normal) Distribution

The positional accuracy attainable in the NTDB will be composed of errors from three sources:

  1. The positional accuracy of the base/reference material
  2. Errors due to the conversion/capture processes
  3. Errors due to the manipulation processes.

Not all data revision/capture/conversion activities will generate errors from all three sources. The following table lists the different activities and their related error sources:

Activity Error Sources
Capturing Vector Features Directly From Raster Imagery
  • The positional accuracy of the base/reference material
  • Errors due to the capture process
Capturing Features Via Vector Conversion Of Raster Imagery
(eg vegetation analysis, vector conversion of scanned repromat)
  • The positional accuracy of the base/reference material
  • Errors due to the conversion process
  • Errors due to the manipulation process (eg smoothing)
Capturing Vector Features Directly From Base/Reference Vector Digital Data
(Note: This means no alteration is conducted on the original spatial representation)
  • The positional accuracy of the base/reference material

The positional accuracy of each feature instance (stated in metres) is given at either the feature level or via a Metadata Index feature class (see '3.6 Feature Metadata' for more details). The standard value assigned for the positional accuracy of features will be the absolute standard deviation (or the root mean square of the standard deviations of the applicable errors) unless the source of the feature is known to have a different accuracy (higher or lower) in which case the value adopted will reflect the expectation. The values to be assigned to these accuracy items should preferably be given at constant metre intervals (e.g. 5, 10, 15) where possible, with provision for smaller intervals in the higher accuracy values (e.g. 1,2,5) etc.

The NTDB's positional accuracy is not restricted to well-defined points but encompasses a feature's entire spatial representation, including locations along a linear feature or the boundary of a polygon feature. This means that point features or point locations along linear features have a 68.27% probability of being within the stated accuracy of the true position of the phenomena they represent. A value of 9999 is used when the positional accuracy of the feature is not definable or not applicable. For example, the coordinates of a connector feature do not carry any meaning with respect to positional accuracy and so the value of planimetric accuracy given is 9999.

Where a feature exists with a populated planimetric accuracy value and is subject to positional change as a result of editing, the respective planimetric accuracy value will be updated accordingly with the appropriate value. A feature should never be revised to a worse planimetric accuracy then it was previously assigned. This value may be sourced from existing base/reference material metadata or as a result of direct capture or digitising from approved reference material eg. a road feature with attributes of "position approximate" (default planimetric value of 9999) in the unrevised database may, upon spatial revision in the NTDB from recent imagery or large scale data sources, have its planimetric attribute updated to a higher value of 100.

3.7.1 The Positional Accuracy of the Base/Reference Material

This specification cannot prescribe a figure for the positional accuracy of the base/reference material designated for the capture of the digital representation of features in the NTDB. This information should be supplied with each revision work package as required.

However there is an expectation that the base/reference material at least complies with the following statement in relation to the scale for which it is being utilised.

Not more than 10% of well defined points will be in error by more than 0.5mm measured on the source material.

Well defined points are those points which are readily identified on the ground and in the data and have not been offset to allow for symbolisation of surrounding features. They are usually at intersections.

Statistically, this relates to a standard deviation at map scale (Sm) of 0.31 mm.(eg 77.5m at 1:250 000, 31m at 1:100 000 and 7.75m at 1:25 000.)

New features will be captured to at least comply with this statement. However, as all data within the NTDB captured at 1:250 000 and smaller scales (larger area) will be utilised for Geoscience Australia's 250K data and map products; all data captured at these scales must comply at a minimum with the accuracy requirements of the 1:250 000 scale.

3.7.2 Errors Due to the Conversion/Capture Processes

The errors due to the conversion/capture process depend on the accuracy of the variety of factors dependant on the type of activity being undertaken. Some of these factors include requested digitising accuracy off imagery/aerial photography, method of raster to vector conversion, digitising table set-up or the scanner resolution, systematic errors in the equipment, errors due to software and errors specific to the operator.

As well as the errors in the conversion process outlined above, linear features may also be subject to filtering as part of the point density reduction process. If the filtering parameters are not carefully selected the resulting linear feature may not retain sufficient likeness to the base/reference material. To ensure linear features which are faithful to the shape and length of the base/reference material, the following specification will be satisfied.

The separation between the feature instance on the base/reference material and its digital representation in the database will not be greater than 0.2 mm at base/reference material scale i.e. 50m for the 1:250 000 data capture, or 20m for the 1:100 000 data capture.

The following is an example of the equation to determine the standard deviation of the conversion/capture process:

When table digitising the accepted standard is that the line accuracy should be within half a line width. As majority of symbolised features in topographic mapping have a line width of 0.2 mm or greater, then half the line width is taken as 0.1 mm and this is interpreted as one standard deviation Sdata for the distribution of errors.

The standard deviation of distribution errors in setting up the digitisation table is determined by the square root of the sum of all residual errors at each of the registration locations squared over the number of registration locations (minus one). For this example the resultant standard deviation measurement Stest is estimated to also be 0.1mm (at map scale).

The errors of the digitising process and the registration system are combined using root-mean-square-error formula to obtain a standard deviation for the entire conversion/capture process 'Slimit' which is a propagation of the known errors.

Conversion Equation

In this example the standard deviation for the entire conversion/capture process is Slimit = 0.14 mm, and thus two standard deviations, which 95 % of points should lie within, is 0.28 mm. The mean of the errors between the data and the test points should be zero, since there should be no bias in the errors, such as a consistent offset in the position of features. A sample of well defined points in data will be compared with their coordinates derived from the base/reference material and a test statistic of the mean plus two standard deviations must not be greater than 0.28 mm.

3.7.3 Errors Due to the Manipulation Processes

Errors due to the manipulation process should be kept at a minimum. Examples of these errors include separating vector contours which have merged in the raster to vector process, correcting topological structure rules such as dangles and intersect errors and as an extreme case smoothing vegetation boundaries after conversion of raster vegetation analysis data.

As a general rule, the processes used during data manipulation should not introduce an error greater than 10% of the vector capture error (e.g Sdata in the example above).

The standard deviation for the error due to the manipulation processes is termed 'Sman'.

3.7.4 Absolute Planimetric Accuracy

A formula is used to obtain the total statistical error from the three errors sources (base/reference material, conversion/capture process and manipulation process). The formula is listed below and an example given where:

  • the standard deviation for the error for base/reference material is given as Sm = 0.31 mm
  • the standard deviation for the error for conversion/capture process is Slimit = 0.14 mm, and
  • the standard deviation for the error for the manipulation process is Sman = 0.05mm .

Absolute Planimetric Accuracy

This example results in a standard deviation of 0.34mm which is approximately what was used to originally capture the TOPO250K GEODATA products and should be used as a guide for other GA activities.

At scale, this represents an error of 85m on the ground for 1:250 000 data capture, 34m for 1:100 000 data capture and 8.5m for 1:25 000 data capture.

Alternative and equal ways of expressing this error, after using the Gaussian Normal Distribution conversion factors is:

  • Not more than 10% of points will be in error by more than 140m for 1:250 000 data, 56m for 1:100 000 data and 14m for 1:25 000 data.

3.7.5 Absolute Elevation Accuracy

The accuracy of the points captured for the Relief layer varies with the source material and the point determination of each particular point. The following table summarises these accuracies.

Type of feature Printed Map Compilation Material Digital Topographic Data
Spot Elevation ±5 metres ±5 metres ±5 metres
Spot Elevation inside Depression contour ±5 metres ±5 metres ±5 metres
Spot Elevation on Sand ridge ±5 metres ±5 metres ±5 metres

The accuracy of the contours is defined as 1/2 of the contour interval, for example ± 25 metres for a 50 metre contour interval and ± 10 metres for a 20 metre contour interval.

3.7.6 Minimum Planimetric And Elevation Accuracies Requirements

The table below defines the minimum planimetric accuracies, where applicable, that must be met for a feature to be allowed to be included in specific Geoscience Australia's scale databases. Where features are captured more precisely than the minimum planimetric and elevation accuracies stated in the specifications this may be indicated by a more reflective value entered into the relevant field. All the planimetric accuracies are defined in metres.

A value of 9999 is used when the positional accuracy of the feature is not definable or not applicable. While the majority of features can be captured with a defined accuracy, others are captured via subjective or arbitrary means. An example of a feature that is captured in a subjective manner is 'Forest Or Shrub' which is based on an individual's interpretation of foliage coverage density. An example of a feature that is captured in an arbitrary manner is a junction between a watercourse area and the sea; this is a defined line by man for which there is no evidence, on the ground, in reality.

FEATURETYPEFeatureClassMinimum Planimetric
Accuracy 25K
Minimum Planimetric
Accuracy 100K
Minimum Planimetric
Accuracy 250K
Limit Of DataContours111
Limit Of DataFrameworkBoundaries111
Horizontal Control PointHorizontalControlPoints101010
Connector StandardContours999999999999
Interpolated ContourContours999999999999
Ferry Route LineFerryRouteLines999999999999
Land Subject To InundationFlats999999999999
Marine SwampFlats999999999999
Saline Coastal FlatFlats999999999999
SwampFlats999999999999
Foreshore FlatForeshoreFlats999999999999
JunctionFrameworkBoundaries999999999999
Large Area FeatureLargeAreaFeatures999999999999
BayLocations999999999999
BeachLocations999999999999
CapeLocations999999999999
GorgeLocations999999999999
PassLocations999999999999
Place NameLocations999999999999
Waterbody IslandLocations999999999999
MainlandMainlands999999999999
ReefMarineHazardAreas999999999999
ShoalMarineHazardAreas999999999999
Forest Or ShrubNativeVegetationAreas999999999999
MangroveNativeVegetationAreas999999999999
RainforestNativeVegetationAreas999999999999
Populated PlacePopulatedPlaces999999999999
Road ConnectorRoads999999999999
SeaSeas999999999999
ConnectorWatercourseLines999999999999
DEMConnectorWatercourseLines999999999999
All Other Feature Types-10 40 100



The table below defines the minimum elevation accuracies, where applicable, that must be met for a feature to be allowed to be included in specific Geoscience Australia's scale databases. Where features are captured more precisely than the minimum planimetric and elevation accuracies stated in the specifications this may be indicated by a more reflective value entered into the relevant field. All the elevation accuracies are defined in metres.

A value of 9999 is used when the elevation accuracy of the feature is not applicable.

FEATURETYPEFeatureClassMinimum Elevation
Accuracy 25K
Minimum Elevation
Accuracy 100K
Minimum Elevation
Accuracy 250K
Bench MarkBenchMarks111
Horizontal Control PointHorizontalControlPoints111
Spot ElevationSpotElevations555
Auxiliary ContourContours51025
Connector DiscontinuityContours51025
Connector StandardContours51025
Depression ContourContours51025
Interpolated ContourContours51025
Standard ContourContours51025
Hypsometric AreaHypsometricAreas51025
Limit Of DataContours999999999999

Where a producer is unable to achieve the minimum planimetric and elevation accuracies with the base material/digital data, reference and supporting material provided an Action Request should be directed to Geoscience Australia requesting additional direction on how to proceed.

3.8 Item Formatting and Attribution

The NTDB's items will be populated in accordance with the following table and the population requirement codes set out in Appendix A Data Attributes Rules for each feature type (see 'An explanation of the feature type dictionary's layout and components. '2. Structure of an Entry'' ).

The Item Name and Item type is listed below, together with a sample attribute and the case of the attribute where applicable (i.e. for text strings). Where domains have been defined, the casing of the defined domain will take precedence but in general the casings of the domain and standard field entries align. No spaces will exist preceding or following any entries in a string field. In addition only single spacing should be used between words.

Where a string field allows Null entries and no information is available to populate that attribute, it must remain as a Null value and not be false 'blank' entry (e.g. a space). In addition, in the same circumstances when an existing attribute value becomes obsolete it should revert back to a Null value.

All date fields should be stored in the Standard Australian Format of DD/MM/YYYY (e.g. 24/10/1999).

Parenthesis should not be included in text strings unless they already exist as part of a defined domain or if they are part of the official or gazetted name. In several states it has become a practice to include an alternate name inside parenthesis as part of the official or gazetted names. This is common during a transition between the replacements of anglo-saxon names with their original indigenous titles, for example 'Tjuwaliyn (Douglas) Hot Spring Park, Uluru (Ayers Rock).

Note: The following list represents the total number of items existing for all Feature Classes and Non Spatial Tables in the NTDB. Therefore, more items are shown than what would normally appear against each individual Feature Class. Users should note that only user-defined items are included and listed below i.e. Default Geodatabase items associated with individual Feature Classes are not included e.g. items such as SHAPE_LENGTH, SHAPE_AREA, ELEMENT and ZCODE will not appear. Individual Feature Classes are not identified in this table (for a fuller description of the NTDB's Data Structure, see Section 3 Chapter 4.0 The National Topographic Database Structure). This list is intended to provide information on the format and attribution of all attribute items in the databases. The items are alphabetically ordered for ease of reference, and are not shown in the order they appear in the NTDBs models.

Case is to be assigned as per the following abbreviations in the table:

Abbreviation Meaning
APS As Per Specified either in associated domain or as part of appendix A
C Caps only
CL Caps & Lower
L Lower case
N/A Not Applicable
SC Sentence Case


Feature Class Item Name Item Type Allow Nulls Precision Scale Length Example Attribute Case
ACCURACY String Yes N/A N/A 20 Calculated Maximum APS
ADMINID Integer Yes 8 N/A N/A 2315 N/A
ADMINNAME String Yes N/A N/A 100 FICKLE STATE FOREST C
AGENCYPID String Yes N/A N/A 10 Icd01234 APS
AIRPORTDESIGNATION String Yes N/A N/A 25 International CL
ALTERNATENAME String Yes N/A N/A 60 HANGMANS FIELD C
ANNOTATIONCLASSID Integer Yes 10 N/A N/A 3 N/A
ASHPONDNUMBER SmallInteger Yes 4 N/A N/A 2 N/A
ATTRIBUTERELIABILITY Date Yes N/A N/A N/A 30/11/2007 N/A
ATTRIBUTESOURCE String Yes N/A N/A 50 XDA PLANIMETRICS C
AUSHYDRO_ID Integer Yes 10 N/A N/A 36485 N/A
AUTHORITY String Yes N/A N/A 100 State Forestry Commission CL
AUXILIARYFUELSYSTEM String Yes N/A N/A 20 Briquettes CL
AVERAGEHEIGHT SmallInteger Yes 2 N/A N/A 6 N/A
BEACON String Yes N/A N/A 100 Beacon: CONCENTRIC.Material: . Vane APS
BLACKSTARTCAPACITY String Yes N/A N/A 7 Yes CL
BOILERNUMBER SmallInteger Yes 4 N/A N/A 4 N/A
BUILDINGFUNCTION String Yes N/A N/A 50 Police Station CL
BUILDINGSTATUS String Yes N/A N/A 12 Operational CL
CAPACITYKV Single Yes 6 2 N/A 66 N/A
CAPTUREMETHOD String Yes N/A N/A 60 GPS APS
CLASS String Yes N/A N/A 40 Secondary Road CL
COALBUNKERNUMBER SmallInteger Yes 4 N/A N/A 6 N/A
CODE String Yes N/A N/A 24 B580 C
COLOUR String Yes N/A N/A 12 B, G, R, W, Y CL
COMMENTS String Yes N/A N/A 1000 Feature deleted as per AR C8432 SC
CONDENSERNUMBER SmallInteger Yes 4 N/A N/A 5 N/A
CONSTRCTMATERIALBDLG String Yes N/A N/A 20 Concrete CL
CONSTRCTMATERIALTANK String Yes N/A N/A 20 Masonry CL
CONSTRCTMATERIALTOWER String Yes N/A N/A 20 Masonry CL
COOLINGDAMNUMBER SmallInteger Yes 4 N/A N/A 6 N/A
COOLINGSOURCE String Yes N/A N/A 20 Pond CL
COOLINGTOWERNUMBER SmallInteger Yes 4 N/A N/A 6 N/A
COOLINGWATERTYPE String Yes N/A N/A 20 Sea Water CL
COOLINGWATERUSAGE Integer Yes 10 N/A N/A 632 N/A
CORRECTIONDATE Date Yes N/A N/A N/A 16/11/2007 N/A
COUNTRYNAME1 String Yes N/A N/A 60 PAPUA NEW GUINEA C
COUNTRYNAME2 String Yes N/A N/A 60 INDONESIA C
COVERDENSITY String Yes N/A N/A 10 Sparse CL
CREATIONDATE Date Yes N/A N/A N/A 30/01/2006 N/A
CROSSINGSTRUCTURE String Yes N/A N/A 20 Arch CL
CURRENCY Date Yes N/A N/A N/A 21/02/2004 N/A
DEMINERALPLANTNUMBER SmallInteger Yes 4 N/A N/A 2 N/A
DESCRIPTION String Yes N/A N/A 30 tower L
DIMENSION Double Yes 15 0 N/A 32642.25 N/A
DURATION String Yes N/A N/A 12 30 C
EDITCODE SmallInteger Yes 5 N/A N/A 2 N/A
EFFICIENCYRATING Single Yes 6 1 N/A 36.1 N/A
ELEVATION Double Yes 7 2 N/A 250 N/A
ELEVATIONACCURACY SmallInteger Yes 4 N/A N/A 5 N/A
ELEVATIONFT Single Yes 6 2 N/A 132 N/A
EMISSIONTOWERNUMBER SmallInteger Yes 4 N/A N/A 4 N/A
EMPLOYEENUMBERS SmallInteger Yes 6 N/A N/A 2000 N/A
ENO Integer Yes 10 N/A N/A 123564389 N/A
ENTEREDBY String Yes N/A N/A 12 F Bloggs CL
ERRONEOUSFEATURETYPE String Yes N/A N/A 32 Watercourse Area CL
ERRONEOUSOID Integer Yes 8 N/A N/A 5784 N/A
ERRONEOUSPID Integer Yes 8 N/A N/A 251 N/A
ERRORNUMBER Integer Yes 6 N/A N/A 14744 N/A
ESA String Yes N/A N/A 10 CRAC C
FACILITIES String Yes N/A N/A 20 With Facilities APS
FEATAREA Double Yes 38 8 N/A 15203 N/A
FEATURE String Yes N/A N/A 32 AircraftFacilityAreas APS
FEATURECLASSESINSPECTED String Yes N/A N/A 255 WaterStoragePoints APS
FEATURECLASSESREVISED String Yes N/A N/A 255 WaterStoragePoints APS
FEATURERELIABILITY Date Yes N/A N/A N/A 20/03/2005 N/A
FEATURESOURCE String Yes N/A N/A 50 IKONOS C
FEATURETYPE String Yes N/A N/A 32 Pipeline CL
FEEDCONVEYORSNUMBER SmallInteger Yes 4 N/A N/A 7 N/A
FIELDINSPECTIONNAME String Yes N/A N/A 50 GOLD COAST C
FIELDINSPECTIONTYPE String Yes N/A N/A 25 Liaison CL
FIELDTEAM String Yes N/A N/A 255 J Birds, R Angry, U Know CL
FLASHES String Yes N/A N/A 12 5 N/A
FLOODLIMITMETRES Double Yes 3 1 N/A 12.5 N/A
FORMATION String Yes N/A N/A 18 Dual Carriageway CL
FUELPRODUCTS String Yes N/A N/A 100 AviationGas Diesel LPG Petrol APS
FUELSOURCELOC1 String Yes N/A N/A 20 Underground CL
FUELSOURCELOC2 String Yes N/A N/A 20 Underground CL
FUELSOURCENAME1 String Yes N/A N/A 60 Weetangra CL
FUELSOURCENAME2 String Yes N/A N/A 60 Weetangra CL
FUELTYPE String Yes N/A N/A 35 Biomass (Animal Waste) CL
FUNCTION String Yes N/A N/A 25 Arterial Road APS
GAUGE String Yes N/A N/A 20 Standard: 1435mm CL
GENERATIONMW Single Yes 6 2 N/A 150.4 N/A
GENERATIONTYPE String Yes N/A N/A 40 Combined Cycle Gas Turbinet APS
GENERATORNUMBER SmallInteger Yes 4 N/A N/A 3 N/A
GNAFID String Yes N/A N/A 15   APS
GROUPSINGLE String Yes N/A N/A 15 Group Obstacle APS
HEIGHT Single Yes 6 2 N/A 51.82 N/A
HEIGHTLIMITMETRES Double Yes 3 1 N/A 12.5 N/A
HIERARCHY String Yes N/A N/A 14 Minor CL
ICAODESIGNATION String Yes N/A N/A 4 ACDO C
IDCODE String Yes N/A N/A 30 A4201 APS
IMPORTANCE String Yes N/A N/A 6 Low CL
INPUTPRODUCTS String Yes N/A N/A 150 Petrol CL
INSPECTIONDATE Date Yes N/A N/A N/A 30/12/2003 N/A
INTERNALPOWERCONSUMP Single Yes 6 2 N/A 0.5 N/A
INVOLTAGEKV Integer Yes 8 N/A N/A 110 N/A
IUCN String Yes N/A N/A 4 VI APS
LANDFILL String Yes N/A N/A 20 Closed CL
LANDINGACCESS String Yes N/A N/A 60 Seasonal CL
LASTRECORDEDUPGRADE SmallInteger Yes 4 N/A N/A 2009 N/A
LATEST_GAZ Date Yes N/A N/A N/A 29/04/2006 N/A
LAYOUTGUIDE String Yes N/A N/A 2 1A C
LIGHTFUNCTION String Yes N/A N/A 12 Rotating beacon SC
LIGHTING String Yes N/A N/A 15 Lighted APS
LIGHTTYPE String Yes N/A N/A 15 ALTN, F, FLG,I, Iso, Mo, Oc,Q APS
MAINTAINER String Yes N/A N/A 50 State CL
MAPNAME String Yes N/A N/A 60 MELBOURNE C
MAPNUMBER String Yes N/A N/A 8 J5505 C
MAPNUMBER100K String Yes N/A N/A 8 J5505 C
MAPNUMBER250K String Yes N/A N/A 8 J5505 C
MAST String Yes N/A N/A 15 With Mast APS
METADATACOMMENT String Yes N/A N/A 1000 All features in this area field checked SC
METADATALINK1 String Yes N/A N/A 400 /ATLAS/fieldpath/subdirectory/filename.doc APS
METADATALINK2 String Yes N/A N/A 400 /ATLAS/fieldpath/subdirectory/filename.doc APS
NAME String Yes N/A N/A 60 ALBURY C
NETWORKID String Yes N/A N/A 10 D653/1 C
NRN String Yes N/A N/A 12 A31, 26 C
NUMBEROFLANES String Yes N/A N/A 15 One Way CL
NUMBEROFPUMPS SmallInteger Yes 3 N/A N/A 12 N/A
NUMBEROFTANKS SmallInteger Yes 4 N/A N/A 6 N/A
OCEANNAME String Yes N/A N/A 20 SOUTH PACIFIC OCEAN C
OPERATIONALUNITS SmallInteger Yes 4 N/A N/A 5 N/A
OPERATOR String Yes N/A N/A 60 PEOPLEPOWER C
ORDEROFACCURACY String Yes N/A N/A 2 00 N/A
ORIGIN String Yes N/A N/A 24 Printed Map CL
OTHERWATERNAME String Yes N/A N/A 22 BASS STRAIT C
OUTPUTPRODUCTS String Yes N/A N/A 150 Petrol CL
OUTVOLTAGEKV Integer Yes 8 N/A N/A 66 N/A
OWNER String Yes N/A N/A 60 PEOPLEPOWER PTY LTD C
PASSENGERCAPACITY Integer Yes 5 N/A N/A 750 N/A
PERENNIALITY String Yes N/A N/A 14 Non Perennial CL
PLANIMETRICACCURACY SmallInteger Yes 4 N/A N/A 100 N/A
PONDLAGOONAREA Integer Yes 8 N/A N/A 7000 N/A
POPULATION Integer Yes 8 N/A N/A 382 N/A
POSTCODE SmallInteger Yes 4 N/A N/A 2064 N/A
PROCLAIMED Date Yes N/A N/A N/A 20/11/1999 N/A
PRODUCER String Yes N/A N/A 50 XYZ Graphics CL
PRODUCT String Yes N/A N/A 35 Gas CL
PRODUCTIONCOMMENTS String Yes N/A N/A 1000 This action was a result of the AR C625 SC
PRODUCTIONFEATURETYPE String Yes N/A N/A 32 Sea CL
PRODUCTIONNUMBER Integer Yes 8 N/A N/A 24 N/A
PRODUCTIONOID Integer Yes 8 N/A N/A 23 N/A
PRODUCTIONPID Integer Yes 8 N/A N/A 24 N/A
PROJECTFILE String Yes N/A N/A 255 //ATLAS/filepath/subdirectory/filename.pdf APS
PROVIDER String Yes N/A N/A 100 QUEENSLAND DEPARTMENT OF STATE FORESTS C
PURPOSE String Yes N/A N/A 20 HYDROLOGY C
RAAFIDENTIFIER Integer Yes 8 N/A N/A 3245 N/A
RAILSTATIONSTATUS String Yes N/A N/A 40 Under Construction CL
RATEDPOWEROUTPUT Single Yes 6 2 N/A 2.11 N/A
REALIGNMENTSTATUS String Yes N/A N/A 25 Original Source Position CL
REBUILDINGTIMEFRAME SmallInteger Yes 4 N/A N/A 36 N/A
REGIONDESCRIPTION String Yes N/A N/A 40 Densely Settled CL
REGULATED String Yes N/A N/A 7 Yes CL
RELATIONSHIP String Yes N/A N/A 12 Underground CL
REPLACEMENTCOST Single Yes 6 2 N/A 624.56 N/A
REPORTYEAR SmallInteger Yes 4 N/A N/A 2009 N/A
REPROCESSING String Yes N/A N/A 20 Operating CL
RESTRICTIONS String Yes N/A N/A 50 Map Use Only CL
REVISED Date Yes N/A N/A N/A 01/01/2006 N/A
REVISIONTYPE String Yes N/A N/A 20 25K Revision CL
REVSOURCE String Yes N/A N/A 50 ALTERNATIVE POWER PTY LTD C
REVSOURCEDATE Date Yes N/A N/A N/A 20/10/2007 N/A
ROADSTATUS String Yes N/A N/A 20 Under Construction CL
ROUTECLASS String Yes N/A N/A 20 Heavy Haulage CL
ROUTENAME String Yes N/A N/A 100 MELBOURNE SYDNEY RAILWAY C
ROUTENUMBER String Yes N/A N/A 12 A31, 26 C
SEANAME String Yes N/A N/A 12 ARAFURA SEA C
SECTIONNAME String Yes N/A N/A 60 CANBERRA TO BOWRAL LINE C
SHOULDERWIDTH Single Yes 4 2 N/A 4.1 N/A
SIGNIFICANCE String Yes N/A N/A 35 National CL
SITEADDRESS String Yes N/A N/A 255 66 Smith Street CL
SITEAREA Integer Yes 10 N/A N/A 632934 N/A
SITECATEGORY String Yes N/A N/A 7 Minor CL
SITEID String Yes N/A N/A 20 325 N/A
SITESUBURB String Yes N/A N/A 40 Balong CL
SPATIALACCURACY SmallInteger Yes 1 N/A N/A 2 N/A
SPEEDLIMITKM SmallInteger Yes 3 N/A N/A 65 N/A
SRCFEATURECLGIDLINK GUID Yes N/A N/A N/A 782324 { -324 9dfj } 324 23 C
SRN String Yes N/A N/A 12 B52 C
STATE String Yes N/A N/A 30 VICTORIA C
STATIONTYPE String Yes N/A N/A 25 Broadcasting Station APS
STATUS String Yes N/A N/A 18 Operational CL
STEPDOWNTRANSFORMERNUM SmallInteger Yes 4 N/A N/A 3 N/A
STKEHDRID String Yes N/A N/A 250 {F1EC17B1-DC4D-4C4D-A1C5-08D54CF54EC7} N/A
STKEHDRNAME String Yes N/A N/A 250 LANDGATE WA C
STORAGECAPACITY Integer Yes 10 N/A N/A 250000 N/A
STORCAPCTYLIQUIDS Integer Yes 10 N/A N/A 500 N/A
STORCAPCTYLPG Integer Yes 10 N/A N/A 1000 N/A
STORCAPCTYOTHER1 Integer Yes 10 N/A N/A 66000 N/A
STORCAPCTYOTHER2 Double Yes 10 2 N/A 66000 N/A
STORCAPCTYRAWPRODUCT Integer Yes 10 N/A N/A 250000 N/A
SUBSETCODE SmallInteger Yes 2 N/A N/A 01 N/A
SUPPLYDELIVERYMETHOD String Yes N/A N/A 20 Pipeline CL
SURFACE String Yes N/A N/A 24 Red Dirt CL
SYMBOL100K LongInteger
(Representation)
N/A N/A N/A N/A 250 N/A
SYMBOL250K LongInteger
(Representation)
N/A N/A N/A N/A 242 N/A
SYMBOLWAC LongInteger
(Representation)
N/A N/A N/A N/A 980 N/A
SYMBOL2_5MIL LongInteger
(Representation)
N/A N/A N/A N/A 33 N/A
SYMBOL5MIL LongInteger
(Representation)
N/A N/A N/A N/A 260 N/A
SYMBOL10MIL LongInteger
(Representation)
N/A N/A N/A N/A 257 N/A
SYSTEM String Yes N/A N/A 75 Radar Responder Beacon CL
TANKAREA Integer Yes 8 N/A N/A 500 N/A
TEXTNOTE String Yes N/A N/A 50 abandoned L
THEMESINSPECTED String Yes N/A N/A 255 Caves, Windpumps APS
THEMESUPDATED String Yes N/A N/A 255 Homesteads APS
TILENAME String Yes N/A N/A 60 GYMPIE C
TILENUMBER String Yes N/A N/A 8 G5606 C
TOURISTTYPE String Yes N/A N/A 50 Emergency Telephone APS
TOWERCOOLINGMAXHEIGHT Single Yes 6 2 N/A 62.52 N/A
TOWEREMISSIONMAXHEIGHT Single Yes 6 2 N/A 143.51 N/A
TRACKNAME String Yes N/A N/A 60 BICENTENNIAL NATIONAL TRAIL C
TRACKS String Yes N/A N/A 8 One CL
TRAFFICABILITY String Yes N/A N/A 20 Seasonality APS
TRANSFERSTATION String Yes N/A N/A 20 Unknown CL
TRANSMISSIONCONNECTIVITY String Yes N/A N/A 100   N/A
TRAVELDIRECTION String Yes N/A N/A 12 One Way CL
TURBINEBUILDINGNUMBER SmallInteger Yes 4 N/A N/A 2 N/A
TYPE_DESCRIPTION String Yes N/A N/A 32 NatureConservationReserve CL
TYPE Integer Yes 5 N/A N/A 3 N/A
UNITCOMMISSIONYEAR SmallInteger Yes 4 N/A N/A 2011 N/A
UPPERSCALE Integer Yes 8 N/A N/A 100000 N/A
USAGES String Yes N/A N/A 75 Civil/Military CL
USCERTAINTY String Yes N/A N/A 25 Indefinite CL
USERACCESS String Yes N/A N/A 10 Restricted CL
VEHICLECAPACITY Integer Yes 5 N/A N/A 53 N/A
VERIFICATIONSTATUS String Yes N/A N/A 30 Verified CL
VOLTAGEKV Integer Yes 8 N/A N/A 250 N/A
VOLUMEMEGAL Single Yes 6 2 N/A 62.2 N/A
WATERTREATMENTTYPE String Yes N/A N/A 20 Tertiary CL
WEIGHTLIMITTONNES SmallInteger Yes 4 N/A N/A 6 N/A
WINDTURBINEMAXBLADEHEIGHT Single Yes 6 2 N/A 43.22 N/A
WINDTURBINEMAXHUBHEIGHT Single Yes 6 2 N/A 46.22 N/A
WORKPACKAGECODE SmallInteger Yes 4 N/A N/A 1020 N/A
WORKPACKAGENAME String Yes N/A N/A 50 WILLOW CREEK C
WORKUNITCODE SmallInteger Yes 4 N/A N/A 0001 N/A
WORKUNITNAME String Yes N/A N/A 50 WILLOWTOWN C
WPCONTACTS String Yes N/A N/A 50 J Bloggs CL
WPWUCODE String Yes N/A N/A 9 1020_0001 N/A
WPWUSSCODE String Yes N/A N/A 12 0194_0192_01 N/A
YEARCOMMISSIONED SmallInteger Yes 4 N/A N/A 2011 N/A

3.8.1 Names

Named features will be attributed with the name in full including the type of feature where it is part of the official name. For example 'ESK RIVER', 'ORANGE AERODROME', etc. Usually the type of feature will not be part of the name for Railway Stations, Populated Places and Place Names that identify centres of population.

Abbreviations must not be used.

In the naming of localities, the terms 'Mission' and 'Aboriginal Community' should be avoided. Source material for the names of Indigenous communities will be determined by Geoscience Australia.

Plural names associated with a group of features should be assigned to every feature in the group unless the individual features have a name in their own right.

In the case of conflicting names, the incompatibility should be resolved and the features named accordingly. The National Gazetteer of Australia will be used to resolve incompatibilities.

Unnamed river anabranches will carry the river's name. Where a river anabranch is named in its own right it will carry its name (e.g. EDWARD RIVER).

Apostrophes should not be included in the NAME field e.g. where a name such as "Mary's Peak" is identified in the approved source material; it will be attributed as MARYS PEAK on entry to the database.

Proper names should not be incorrectly abbreviated or truncated eg. where a name such as "MacDonald River" is identified in the approved source material, it will be attributed as MACDONALD RIVER (not MCDONALD RIVER) on entry to the database.

Terms such as Mount and Saint shall be entered in full unless the official authorised name includes these terms as abbreviations e.g. the official name of a locality in Queensland is 'St George' whereas the official name of a locality in Victoria is 'Saint Albans East'.

The generic words "Mount" and "Mountain" should not be abbreviated when used to populate or complete Mountain names eg. the proper names "Mount Frederick" and "Jackson Mountain" should, on entry to the database, be fully attributed as MOUNT FREDERICK and JACKSON MOUNTAIN (not MT FREDERICK or JACKSON MTN).

3.9 Edge Match

The process of edge matching features in the NTDB involves the examination of the spatial and attribute properties of features either side of the Limit Of Data feature, work package/unit extents or across mismatches caused by spatial extent of revision material and, where appropriate, merging them into a single feature.

Linear and polygon features should be spatially joined across the Limit Of Data feature, work package/unit extents or across mismatches caused by spatial extent of revision material, if they are the same entity and within a specified distance determined by the data capture scales used on either side of the join. The smallest scale (larger area) capture scale used, on either side of the join, will determine the maximum distance between features allowable for edgematching, the distances for edgematching will be 140m for 1:250 000 or smaller scales (larger areas), 56m for 1:100 000 and 14m for 1:25000. In general, the older data should be adjusted to match the most recent data, taking into account any locational reference material available such as imagery or digital photography. This makes the assumption that the most recent data has the best planimetric accuracy, where this is not the case and no direction is provided in the work package project instructions, a request should be made to Geoscience Australia on how to proceed. The adjustments made should result in a smooth transition of the join without hard bends appearing in the line work. The objective is to improve or establish continuity of features inside the NTDB.

Some feature mismatches are unable to be immediately resolved and edge matched on entry to the databases for various reasons eg. Lack of sufficiently accurate source revision material, suitably revised data is unavailable for matching with the database area as it is currently being revised etc - hence the requirement for the Limit Of Data features.

All cases of mismatches need either a production note or error note associated with them dependant on the identifier or creator of the mismatch (e.g. through internal NMD personnel or those acting in a similar role/capacity an error note should be used however external producers should note these cases by using a production note). Systematic causes of spatial mismatches, such as the application of the incorrect datum when loading should be noted by only sufficient notes to identify the full extent of the problem.

3.10 Spatial Data Integrity

The NTDB vector data will comply with the following rules for spatial data integrity. The rules for maximum allowable errors are described in Appendix J. These rules will be enforced with a 95% confidence level.

The spatial data will have no overshoots, undershoots, broken lines, pseudo nodes or other artefacts of the data capture process. These possible errors in the data are illustrated below. Pseudo nodes will be acceptable where features attributes vary with the exception of feature level metadata (e.g. feature reliability).

Undershoot in data.

Undershoot in Data

Correct Representation           Incorrect Representation

Overshoot in data.

Overshoot in Data

Correct Representation           Incorrect Representation

Pseudo-node in data

Pseudo node
Pseudo Node

Same feature with identical attribute values.

Broken line in data

Correct Representation
Broken Line
Incorrect Representation

Artefacts

Artefacts in Lines

Correct Intersection   Incorrect Intersection   Incorrect Intersection

Spikes in Lines

Linear Feature       Spike in Linear Feature

Artefacts such as spikes and deviations of a linear feature from its expected position will be removed from the data to the extent that they will not be visible when the data is plotted or displayed at half its nominal scale i.e. 1:125 000 for 1:250 000 data, or 1:50 000 for 1:100 000 data.

  • All linear features within the same feature dataset will be broken by a node at intersections or at the point where an attribute of the feature changes. A node will exist at these intersection points.
  • All polygon boundaries must be closed.
  • Abutting polygons will not have an identical set of attributes.
  • Within a Feature Class there will be no coincident features of the same spatial object type, for example, a line cannot be coincident with another line.
  • Two features in separate feature classes, which share the same physical position on the source material, will have coincident spatial addresses.

3.10.1 Valid Intersections

An intersection in digital data will contain the same number of nodes as shown on the source material. An intersection node will be within 1/6 of the line width of the centre position of the intersection. The first vertex in each direction from the intersection node will be at a distance greater than three times the line width unless there is a bend in the road before this distance.

Intersection

Valid and Invalid Intersections

Valid Intersection

3.10.2 Data Acquisition and Positioning of Features

When capturing data from imagery and photography as well as other sources such as GPS readings, wherever possible a:

  • point should be positioned central to the feature it represents (e.g. A building point should be captured at the centre of the roof extent)
  • line should be positioned along the centre of the feature it represents (e.g. A road should be captured along its centreline not along one bounding edge of the easement)
  • polygons should be captured to the outer rim of the feature it is representing (e.g. The high water mark of a reservoir (its maximum capacity), not its current water level at the time of the image as this can be affected by drought, seasonal factors, etc.)

4. Quality Information

Quality information allows the users of the data to make informed decisions about the fitness of the data for their application.

4.1 Product Quality Information

Product Quality Information will provide information which is specific to the NTDB. Geoscience Australia will provide the Product Quality Information. This will include a history of the source material, a description of the data capture process, and the quality aspects inherent in the NTDB such as positional accuracy, attribute accuracy, logical consistency and completeness.

5. Data Arrangement

The NTDB forms part of a national digital spatial data environment for use by all users of digital spatial data. The features included in the NTDBs structure are arranged in Feature Datasets, Feature Classes and Feature Types as detailed in Section 3 of the Specification (see Section 3 Chapter 4.0 The National Topographic Database Structure)

For more information on feature classes and associated attributes see Appendix A.

Topic contact: mapfeedback@ga.gov.au Last updated: January 20, 2012