Section 1 - TOPO250K and TOPO100K National Topographic Databases Structure and Specifications

1. Scope of this document

This document sets out the Technical Specification for Geoscience Australia's TOPO250K and TOPO100K National Topographic Databases (NTDBs).

This specification sets out the minimum quality standard for the data in terms of its planimetric and altimetric accuracy, geometrical aspects, feature content, topological structure and the rules used in the collection and attribution of the data.

The 1:250 000 scale NTDB spatial data was sourced from the Series 2 TOPO250K vector product GEODATA and its associated working database produced by Geoscience Australia between the years 1997 and 2005. This data has been concatenated to form a Geodatabase at 1:250 000 scale, titled "TOPO250K", with uninterrupted layers covering the entire nation. The specification covers the maintenance and revision aspects related to the TOPO250K NTDB as well as its outputs, primarily the National Topographic Map Series (NTMS) published by Geoscience Australia.

The 100 000 scale NTDB spatial data will be progressively constructed, loaded and concatenated to form a semi-seamless database at 1:100 000 scale, titled "TOPO100K" . The TOPO100K will contain layers covering the majority of urban and urban fringe areas as well as areas required for strategic planning purposes. The population of the 1:100 000 NTDB is expected to commence in 2006. The component data is derived from published 1:100 000 topographic maps updated with information from Geoscience Australia and other agencies, together with a range of various digital data sources. The bulk of these source maps are from the National Topographic Map Series (NTMS) published by Geoscience Australia / AUSLIG and the Royal Australian Survey Corps. However, where agreements have been made with state mapping agencies, the state mapping paper or digital data products may have precedence for use as the main source dependant on a number of factors.

The TOPO250K and TOPO100K NTDBs are managed by the Oracle Relational Database Management System (RDBMS) and ESRI's ArcSDE software. They contain the relevant data tables and indexes.

These NTDBs:

• are used for the revision and maintenance of topographic mapping data at 1:250 000 and 1:100 000 scale.
• are used to revise and generate the National Topographic Map Series products, together with customised maps as required.
• must comply with the standards and rules set out in the TOPO250K and TOPO100K NTDB Specifications and its associated Appendices.

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2. The NTDB Model

2.1 The Feature-Based Data Model

The TOPO250K and TOPO100K NTDBs are feature-based data models. The following definitions describe the components of the NTDBs:

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 ie. 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 NTDBs using Points, Lines and Polygons. Multi-Polygons can also exist in the databases. 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.
Node - A point that is an intersection of two or more chains or an end point of a chain.
Vertex - A point that is a change of direction along the length of a chain.
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.
Polygon
A defined continuous region consisting of an interior area and zero or more nested 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. There are three feature classes where multi-polygon features apply, these are Reserves, Built Up Area and Islands.

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
	Attribute Reliability:	22/08/2002
	Planimetric Accuracy:	100
	Source:	GEOSCIENCE AUSTRALIA
	UFI:	BB53410688
	Creation Date:	22/04/2003
	Retirement Date:	16/12/2003
	PID:	23602884
	Symbol:	252
	Feature Width:	0.9
	Text Note:	under construction

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
	Attribute Reliability:	14/10/2002
	Planimetric Accuracy:	9999
	Source:	GEOSCIENCE AUSTRALIA
	UFI:	BA32610473
	Creation Date:	22/05/2002
	Retirement Date:	14/03/2004
	PID:	12090076
	Symbol:	908
	Text Note:	marine swamp

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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 TOPO250K and TOPO100K NTDBs are primarily derived from a combination of existing map production material, base digital data, imagery and authorised source material. The data on the source material may be divided into themes, each theme containing logically related geographic information. On entry to these NTDBs, features are grouped under Feature Datasets which bring together those features sharing a close topological relationship and common "theme" ie. features are broadly categorised according to their physical or cultural similarities. There are twenty Feature Datasets in the TOPO250K and TOPO100K NTDBs, namely:

Administration Aviation Cartography Culture Drainage Errors Framework	Habitation Industry Marine Physiography Production RailTransport Relief	RoadTransport SeriesIndex SurveyMarks Utility Vegetation Waterbodies

2.2.2 Feature Classes

All TOPO250K and TOPO100K NTDB vector data is topologically structured and this is reflected in the way the data is structured and transferred to the client. Feature classes are composed of different spatial objects and convey the topological relationships of the data. There are one hundred and ten feature classes in the TOPO250K NTDB, with features having up to eighteen attributes.

The NTDBs 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 chain feature classes) representing features such as lakes or built-up areas.

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

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3. TOPO250K and TOPO100K Data Structure

The TOPO250K and TOPO100K NTDB vector data is topologically structured and additional information about the features will be conveyed by attributes which are held at the feature level.

All TOPO250K and TOPO100K NTDB vector data share a number of common formats and characteristics which are set out below.

3.1 Datum, projection and co-ordinate extents

The datum used in the NTDBs is GDA94, and the projection is geographicals ie. latitudes and longitudes. A single spatial index is used. This is a grid of side length 0.5 degrees, for all Feature Classes except the Sea, Mainland and Hypsometric Areas Feature Classes. These feature classes have a side length of 1.5 degrees. The extent of the database is specified as 0 to -48 degrees of latitude and 108 to 156 degrees of longitude. Features within these limits can be accommodated.

3.2 Data projection and editing

It is important to note that in most cases (ie. 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

The precision of the NTDB is 0.000001 degrees, which equates to approximately 0.1 metres on the ground. This value is determined by dividing 1 coordinate system unit (degree) by the scale of the data. 1 degree / 1000000 = 0.000001 degrees.

The scale of the geodatabase is inversely related to its Spatial Domain. 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: 108.000000
Minimum Y: -48.000000
Maximum X: 2255.483645
Maximum Y: 2099.483645

Scale: 1000000.000000

The coordinate precision 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.

The following specifications apply for data point reduction:

• The length of a line segment will be equal to, or greater than 0.000 22 degrees (approx. 25m) for the 1:250 000 product and 0.000 10 degrees (approx. 10m) for the 1:100 000 product. However, for features other than roads, feature instances of less than 20 points will not be filtered (i.e.: such features are an exception to this rule). Sections of the chains, which must be coincident with such features, will also be an exception to the rule.
• The length of a line segment will not be greater than 0.253 68 degrees (approx. 20 000m for the 1:250 000 product and 0.147 degrees (approx 8000m) for the 1:100 000 product).
• For Limit of Data features in all layers the distance between vertices will not exceed 0.002 degrees (approx. 200m).

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3.5 Persistent Identifier Attribute and Incremental Update

The TOPO250K and TOPO100K NTDBs will use a Persistent Identifier (PID) attribute to identify individual features inside the NTDB. This PID will be unique on a national basis and is expected, in conjunction with two other fields named Creation Date and Retirement Date, to facilitate the efficient incremental update of database features.

The Persistent Identifier will be assigned to each feature as the databases are populated. The PID will be maintained when a feature's attributes change. The PID will only be retired as a result of changes when this is unavoidable eg. when a linear feature is split into two features or when two features are merged. The PID will be maintained when the spatial representation of the feature changes but logically the feature is the same.

For example:

• for a linear feature if the start node and end node are the same.
• if the real world feature is unchanged but the database representation changes.

When a feature changes and the PID can be maintained, the feature will be retired from the database and a new feature with same PID and a new Creation Date created. There may therefore be multiple representations of a feature in the database histories but only one will be valid at any point in time. Creation Date will have no relation to the date on which the feature physically came into existence, for example, the date of completion of a building. Creation Dates will be populated for all features.

A feature will be retired when it no longer exists in the real world, is being replaced by a new feature instance due to change to the feature, or otherwise is no longer required in the active data. In general, it will have no relation to the date on which the feature was physically destroyed, for example, the date of demolition of a building. The Retirement Date will be when the feature is marked as retired. Retirement Dates will be populated for all features other than active features, and be null for active features. There will be only one active instance in the data at any time for any given feature.

The combination of PID, Creation Date and Retirement Date will be unique within the NTDBs. The Creation Date and Retirement Date will be system generated. The intention is for the PID to also be system generated and therefore, at this stage, producers are not required to populate this item.

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3.6 Feature Level Metadata

The TOPO250K & TOPO100K NTDBs store metadata at a feature level. Apart from the standard system generated attribute fields, the following fields will always apply for each feature, at the feature level. The exception will be features within the Cartography, Errors, Production and Series Index Feature Datasets.

Planimetric accuracy

This is the standard deviation in metres of the position of the feature's horizontal coordinates (PLANIMETRICACCURACY) [Short Integer; No; 4; Pop_Req].( See Section 1 Chapter 3.7 "Positional Accuracy")

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 is confirmed, regardless of whether the feature needed editing on inspection to meet its positional accuracy requirements (FEATURERELIABILITY) [Date; Yes; 0; 0; 36; Pop_Req].

Feature source (TOPO100K only)

This is the latest primary source used to determine the spatial location of a feature. Feature Source and Feature Reliability are inter-linked.The date of the latest primary source, used to add, update or verify a feature existance or position, will be the date used to complete the feature reliability field entry for that feature. (FEATURESOURCE) [String; Yes; 50; Pop_Req]

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. (ATTRIBUTERELIABILITY) [Date; Yes; 0; 0; 36; Pop_Req]. (see Section 1 Chapter 3.6.1 "Attribute Reliability and Attribute Source")

Attribute source (TOPO100K only)

This is the latest primary source material used to populate the attribute field/s of a feature. (ATTRIBUTESOURCE) [String; Yes; 50; Pop_Req] (see Section 1 Chapter 3.6.1 "Attribute Reliability and Attribute Source")

Source (TOPO250K only)

This is the official name of the agency that originally captured the spatial object for the TOPO250K NTDB. The default value when unknown or not specified in the Project Instructions will be Geoscience Australia. (SOURCE) [String; No; 50; Pop_Req]

Elevation accuracy

This is the standard deviation in metres of the feature's elevation attribute value. This applies only to those features with an elevation attribute. (ELEVATIONACCURACY) [Short Integer; No; 4; Pop_Req](see Section 1 Chapter 3.7 "Positional Accuracy")

If the latest primary source material (for either feature positioning or attribution) 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 TOPO250K 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.

The dates (for the FEATURERELIABILITY and ATTRIBUTERELIABILITY items) and attributes (for the FEATURESOURCE and ATTRIBUTESOURCE items) to be assigned for each FeatureType will be determined for each project by Geoscience Australia and instructions provided in the respective Project Instructions issued to the producers, or included in the supplied source revision data.

The values (for the PLANIMETRICACCURACY and ELEVATIONACCURACY items) may be determined for each project by Geoscience Australia and instructions provided in the respective Project Instructions issued to the producers, or included in the supplied source revision data. Otherwise they will default to those values indicated in each entry within Appendix A 2. Feature Type Dictionary

The values and dates already assigned to features in the TOPO250K NTDB (sourced from the Series 2 TOPO250K GEODATA product) will by default be retained in the NTDB and will be subject to revision in accordance with the supplied Project Instructions/revision data. New values to be assigned for the TOPO100K NTDB will be as per the Project Instructions.

Values to be assigned for the planimetric and elevation accuracy items 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.

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3.6.1 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 symbol value for a feature is added, revised or confirmed, then the attribute source and attribute reliability fields will not be updated because the symbol 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 28 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	DESCRIPTION	DESCRIPTION
4	BUILDINGFUNCTION	BUILDING FUNCTION
5	HEIGHT	HEIGHT
6	NAME	NAME
7	STATUS	STATUS
8	CLASS	CLASSIFICATION
9	ELEVATION	ELEVATION
10	TRACKS	TRACKS
11	AUTHORITY	CONTROLLING AUTHORITY
12	FORMATION	FORMATION
13	GAUGE	GAUGE
14	PERENNIALITY	PERENNIALITY
15	PRODUCT	PRODUCT CODE
16	CODE	CODE
17	HIERARCHY	HIERARCHY
18	OTHERWATERNAME	OTHER WATER NAME
19	RELATIONSHIP	RELATIONSHIP
20	TEXTNOTE	TEXT NOTE
21	GROWTHFORM	GROWTH FORM
22	NRN	NATIONAL ROUTE NUMBER
23	SRN	STATE ROUTE NUMBER
24	SEANAME	SEA NAME
25	OCEANNAME	OCEAN NAME
26	ORDEROFACCURACY	HORIZONTAL ORDER
27	STATE	STATE/TERRITORY
28	COVERDENSITY	FOLIAGE COVER DENSITY

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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 agree with their real world values. The planimetric accuracy attainable in the TOPO250K and TOPO100K NTDBs will be composed of errors from three sources:

1. The positional accuracy of the source material; and
2. Errors due to the conversion processes; and
3. Errors due to the manipulation processes.

The planimetric accuracy of each feature instance (stated as a standard deviation in metres) is given at the feature level. The standard value for the features will be the standard deviation 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. 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.

In addition to satisfying the standard deviation for well defined points as discussed in the later chapters, linear segments defining portions of linear features and area boundaries should be representative of the feature's true ground position at scale.

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. This value may be sourced from existing source metadata or as a result of direct capture or digitising from approved sources 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 Source Material

This specification cannot prescribe a figure for the planimetric accuracy of the source material (repromat) used for capture of the TOPO250K NTDB source data ie. the TOPO250K GEODATA Series 2 Vector product, as it has already been produced. Note: the TOPO100K NTDB will be populated from both the TOPO100K GEODATA Series 1 Vector product and other miscellaneous data or repromat. There is an expectation that the source data complies with the following statement.

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 on the map (S_m) of 0.31 mm.

New features will be captured to comply with this statement.

3.7.2 Errors Due to the Conversion Processes

The errors due to the digitising process depend on the accuracy of the digitising table set-up or the scanner resolution, systematic errors in the equipment, errors due to software and errors specific to the operator. An accepted standard for digitising is that the line accuracy should be within half a line width. The majority of features have a line width of 0.2 mm or greater. The half line width is taken as 0.1 mm and this is interpreted as one standard deviation S_data for the distribution of errors.

The expectation is that the degradation caused by the scanning processes will be minimal and will be the result of thinning lines to a co-ordinate string. This may result in an added error of +/- 0.2 mm for the thickest lines digitised.

The inaccuracy in setting up the test digitisation and making the measurement S_test is estimated to be in the same order of inaccuracy as the digital data being checked. The errors of the digital data and the system used to check this digital data combine using the formula.

The limit for the standard deviation of the measured errors, S_limit = 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 source material and a test statistic of the mean plus two standard deviations must not be greater than 0.28 mm.

As well as the errors in the conversion process outlined above, linear features are also 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 source material. To ensure linear features which are faithful to the shape and length of the source material, the following specification will be satisfied.

The separation between the feature instance on the source material and its digital representation in the database will not be greater than 0.2 mm at source material scale ie. 50m for the TOPO250K NTDB, or 20m for the TOPO100K NTDB.

3.7.3 Errors Due to the Manipulation Processes

The processes used during data manipulation will introduce an error S_man not greater than 10% of the S_data.

3.7.4 Absolute Planimetric Accuracy

The total statistical error from the source material and digitising process (Sd) discussed above is given by:

This represents an error of 85m on the ground for 1:250 000 data and 34m for 1:100 000 data.

Alternative and equal ways of expressing this error are:

• Not more than 10% of well defined points will be in error by more than 140m for
  1:250 000 data and 56m for 1:100 000 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
Horizontal Control Point			±15 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.

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3.8 Item formatting and attribution

NTDB items will be populated in accordance with the following table and the population requirements 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 (ie. for text strings). No spaces will exist preceding or following any entries in a character field. In addition only single spacing should be used between words.

Note: The following list represents the total number of items existing for all Feature Classes in the NTDBs. 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 NTDBs Data Structure, see Section 3 Chapter 4.0 The National Topographic Datatbase Structure). This list is intended to provide information on the format and attribution of all attribute items in the database. The items are alphabetically ordered for ease of reference, and are not shown in the order they appear in the NTDBs models.

Items applicable for only one of the database scales (ie. TOPO250K or TOPO100K) are indicated in italics eg. (250K only)

The Item attribute type 'Text' is synonymous with a String attribute.

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

Abbreviation	Meaning
C	Caps only
CL	Caps & Lower
L	Lower case
N/A	Not Applicable
MR	Annotation item - to be shown in the same case as required for map production

** These attributes will not be supplied for NTDB production purposes

Feature Class Item Name	Item Type	Allow Nulls	Precision	Scale	Length	Example attribute	Case
ANNOTATIONCLASSID	Long Integer	Yes	10			<null>	N/A
ATTRIBUTERELIABILITY	Date	Yes	0	0	36	1/10/2000	N/A
ATTRIBUTESOURCE (100K only)	String	Yes	0	0	50	XDA PLANIMETRICS	C
AUTHORITY	String	Yes			100	State Forestry Commission	CL
AVERAGEHEIGHT	Short Integer	Yes	2			6	N/A
BUILDINGFUNCTION (100K only)	String	No			50	Police Station	CL
CLASS	String	No			40	Secondary Road	CL
CODE	String	Yes			24	NSW1274	C
COMMENTS	String	No			1000	Polygon has incorrect name should be RJ Creek	CL
CORRECTIONDATE	Date	Yes	0	0	36	22/03/2004	N/A
COVERDENSITY (100K only)	String	Yes			20	Sparse	CL
CREATIONDATE	Date	Yes	0	0	36	16/11/2003	N/A
DALIGN	String	Yes			10	LEFT	C
DESCRIPTION	String	Yes			30	tower	L
DFIT	String	Yes			4	OFF	C
DID	Long Integer	Yes	9			14	N/A
DJUSTIFY	String	Yes			2	LR	C
DLEVEL	Long Integer	Yes	9			1	N/A
DOFFSETX	Double	Yes	18	11		300	N/A
DOFFSETY	Double	Yes	18	11		20	N/A
DSIZE	Double	Yes	18	11		787.5	N/A
DSYMBOL	Long Integer	Yes	9			10	N/A
DTEXT	String	Yes			254	No. 19 Bore	MR
EDITCODE **	Short Integer	Yes	2			4	N/A
EDITDATE **	Date	Yes	0	0	36	24/10/2003	N/A
ELEMENT	Blob	Yes	0	0	21474 83647	Images & general graphics etc	N/A
ELEVATION	Double	No	7	2		250	N/A
ELEVATIONACCURACY	Short Integer	No	4			25	N/A
ENTEREDBY	String	No			12	f bloggs	L
ERRONEOUSFEATURETYPE	String	No			32	Watercourse Area	CL
ERRONEOUSPID	Long Integer	No	8			578	N/A
ERRONIUSOID	Long Integer	No	8			5784	N/A
ERRORNUMBER	Long Integer	No	6			14744	N/A
FEATURECLASSNAME	String	Yes			50	Sea	C/L
FEATUREID	Long Integer	Yes	10			14744	N/A
FEATURERELIABILITY	Date	Yes	0	0	36	1/02/2000	N/A
FEATURESETNAME	String	Yes			50	Framework	C/L
FEATURESOURCE (100K only)	String	Yes	0	0	50	IKONOS	C
FEATURETYPE	String	No			32	Pipeline	CL
FEATUREWIDTH	Double	Yes/No (variable)	8	4		0.25	N/A
FORMATION	String	No			18	Unsealed	CL
GAUGE	String	No			20	Standard: 1435mm	CL
GROWTHFORM (100K only)	String	Yes			20	Mallee Shrub	CL
HEIGHT	Float	Yes	6	2		51.82	N/A
HIERARCHY	String	No			14	Minor	CL
IDCODE	String	Yes			30	A4021	N/A
IMPORTANCE	String	Yes			6	low	L
LAYOUTGUIDE	String	Yes			2	1B	C
MAPNAME	String	Yes			60	PORT PHILLIP SPECIAL	C
MAPNUMBER	String	Yes/No (variable)			8	H5002	C
NAME	String	Yes/No (variable)			60	ALBURY	C
NRN	String	Yes			12	A31, 26	N/A
OBJECTID (system generated)	Object ID					2453	N/A
OCEANNAME (100k only)	String	Yes			60	SOUTH PACIFIC OCEAN	C
ORDEROFACCURACY	String	Yes			6	3	N/A
ORIENTATION	Short Integer	Yes	3			135	N/A
OTHERWATERNAME(100k only)	String	Yes			60	BASS STRAIT	C
PERENNIALITY	String	No			14	Non-perennial	CL
PID	Long Integer	Yes	8			83202692	N/A
PLANIMETRICACCURACY	Short Integer	No	4			100	N/A
PRODUCER	String	Yes			50	XYZ Graphics	CL
PRODUCT	String	Yes			35	Gas	CL
PRODUCTIONCOMMENTS	String	Yes			1000	This action was a result of the direction in A/R C625	CL
PRODUCTIONFEATURETYPE	String	Yes			32	Sea	CL
PRODUCTIONNUMBER	Long Integer	Yes	8			23	N/A
PRODUCTIONOID	Long Integer	Yes	8			23	N/A
PRODUCTIONPID	Long Integer	Yes	8			23	N/A
RELATIONSHIP	String	Yes			12	Underground	CL
RETIREMENTDATE	Date	Yes	0	0	36	12/01/2004	N/A
SEANAME (100k only)	String	Yes			60	ARAFURA SEA	C
SHAPE	Geometry	Yes				Polygon	N/A
SHAPE.AREA	Double	No	0	0		0.738476	N/A
SHAPE.LEN	Double	No	0	0		0.409136	N/A
SOURCE (250k only)	String	No	0	0	50	GEOSCIENCE AUSTRALIA	C
SOURCETYPE	String	No			24	PRINTED MAP	C
SRN	String	Yes			12	M13, 64	N/A
STATE	String	No			3	NSW	C
STATUS	String	No			18	Operational	CL
SYMBOL	Short Integer	No	4			209	N/A
TEXTNOTE	String	Yes			50	gauge 1435mm	L
TILENAME	String	Yes			60	MELBOURNE	C
TILENUMBER	String	No			8	F5416	C
TRACKS	String	No			8	One	CL
TYPE	Long Integer	No	5			2	N/A
TYPE_DESCRIPTION	String	No			32	NatureConservationReserve	CL
UFI (250K only)	String	Yes			10	BD51401745	C
ZORDER	Long Integer	Yes	10			0	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 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 (eg. EDWARD RIVER).

Apostrophes should not be included in the NAME field eg. 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.

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).

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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 (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 (or across mismatches caused by spatial extent of revision material) if they are the same entity, and within 140m at 1:250 000 or 56m at 1:100 000 of each other in the data. The older data should be adjusted to match the most recent data, taking into account any locational source material available such as imagery or digital photography. 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 NTDBs.

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.

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3.10 Spatial Data Integrity

TOPO250K and TOPO100K 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.

Correct Representation Incorrect Representation

Overshoot in data.

Correct Representation Incorrect Representation

Pseudo-node in data

Pseudo node

Same feature with identical attribute values.

Broken line in data

Correct Representation

Incorrect Representation

Artefacts

Correct Intersection   Incorrect Intersection   Incorrect Intersection

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 ie. 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.

Valid and Invalid Intersections

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.)

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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 TOPO250K and TOPO100K NTDBs form 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 Datatbase Structure)

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