GDA Implementation Statement

• Overview
• General Implementation Policy
• Paper Maps
• Digital Map Data
• Digital Elevation Model Data
• Administrative Boundary Data
• Maritime Boundary Data
• Resource and Environ Data
• Place Names Data
• Remote Sensing
• Geodetic Services

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Overview

Geoscience Australia fully supports the Inter-governmental Committee on Surveying and Mapping (ICSM) resolution to adopt the GDA by the year 2000. This will result in an approximate shift of 200 metres to the northeast in Australia's coordinate system.

Geoscience Australia has adopted the GDA and considers the GDA is the most effective datum for all users of spatial data as it provides:

• Compatibility with satellite navigation systems;
• Local, regional, state, national and international compatibility through having one consistent reference frame for all users;
• The reference frame on which the Australian Spatial Data Infrastructure (ASDI) is to be based;
• and Infrastructure to support international agreements.

As such, Geoscience Australia is committed to progressively migrating its products and services across to GDA up to and beyond the year 2000. Because of the lead time required to convert paper based products to GDA it will not be possible to reissue all maps on GDA by the year 2000. Geoscience Australia will however provide information to users which will assist them during this transition period and ensure there is no immediate need to replace existing paper products.

Geoscience Australia fully supports providing digital data to clients in their preferred formats and where practical will continue to support existing formats and translations up to and beyond the year 2000. Geoscience Australia will also endeavour to provide clients with sufficient information and product support to enable clients to smoothly migrate to GDA from these existing Geoscience Australia Australian Geodetic Datum (AGD) based products.

From 1997 all new products from Geoscience Australia are, or can be provided on, the GDA datum.

As individual product transition strategies are refined over the next couple of months, clients will be kept informed of these initiatives through Geoscience Australia's standard publications (Data Directions, Retailer News, ACRES Update, Distributor Bulletin, Geoscience Australia Directions) and via the Geoscience Australia web site.

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General Implementation Policy

Paper Map Products - All maps published after 1996 are on GDA94 coordinates and all future maps will be produced on GDA. The difference between AGD and GDA maps is only significant at scales of 1:250 000 or larger. Due to the long cycle of topographic map revision, it will be at least 2006 before all 1:250 000 scale maps are on GDA and even longer (> yr 2015) for the 1:100 000 scale products. Geoscience Australia will produce ready reckoners to help map users convert coordinates between both datums. Download Geoscience Australia's coordinate conversion tables.

Digital Data Products - All new Geoscience Australia digital data products will be produced on GDA. The difference between AGD and GDA maps is only significant at scales of 1:250 000 or larger. Some older products will not be converted to GDA. Some products will be maintained in both GDA and AGD versions for a period of time before AGD versions are phased out. Geoscience Australia will provide advice to help customers convert old data sets to GDA and new data sets to AGD if required.

Remote Sensing Products - Geoscience Australia produces both geocoded and non-geocoded image products. The adoption of GDA is only relevant for Geoscience Australia's geocoded products. Products are available from February 1998 in both AGD and GDA at customers' choice. AGD may eventually be phased out. Geoscience Australia can provide advice on block shifts applicable to customer's existing geocoded images to convert them between AGD and GDA. Details of block shifts (by 1:250 000 map sheet area) can be obtained from the Geoscience Australia coordinate conversion tables.

Geodetic Products and Services - Geoscience Australia's geodetic products are already GDA compatible as they provide the foundation for GDA. The GDA94 coordinates of the Australian Fiducial and National Networks (AFN and ANN) were used to constrain the readjustment of the national geodetic network, providing thousands of GDA94 coordinates which are being used by State and Territory authorities to convert their survey networks to GDA. Historical data sets (AGD66, AGD84 etc) as well as the new GDA94 coordinates, will continue to be maintained in the National Geodetic Data Base (NGDB). Geoscience Australia, cooperating with other ICSM members, is producing the GDA Technical Manual, which contains algorithms, transformation parameters and worked examples.

Paper Map Products

Product	GDA Compliant
1:100 000 NATMAP Topographic Map Series	No The maps in this series are based on AGD66 coordinates. More maps will be converted to GDA94 coordinates as they are digitally revised. As there are more than 1600 published maps in the 1:100 000 series, many of these maps will remain on AGD66 coordinates for a considerable time to come.
1:250 000 NATMAP Topographic Map Series	Some Geoscience Australia is currently revising the 1:250 000 scale map series and all maps revised by Geoscience Australia will be based on GDA94 coordinates. It is estimated that it will take Geoscience Australia eight years to revise the 540 maps which make up the series. Some Army produced maps, currently in this series, are based on WGS84 coordinates which are the same as GDA94 coordinates for all practical purposes. All maps in this series produced since 1996 are GDA compliant.
Small Scale General Reference & Tourist Mapping	Yes The effect of the datum change on all map products at scales smaller than 1:250 000 (small scale maps) is considered to be negligible. This means that the change in coordinate is less than the accuracy of the original data.
Medium Scale Tourist and Specialty Maps	No A number of medium scale tourist maps are produced by Geoscience Australia including the Kakadu and Uluru National Park Maps. These maps will be converted to GDA94 coordinates when they are digitally revised.
1:50 000 Topographic Maps	Some These maps are produced by the Department of Defence's Directorate of Strategic Military Geographic Information - Army (DSMGI-A). Maps in this series vary between local datum (AGD66) and geocentric datum (WGS84). Maps are being converted to WGS84 as they are revised. WGS84 is essentially the same as GDA94.

Please Note: Users wishing to know the datum of a particular map sheet, can contact Geoscience Australia Map Sales by emailing : mapsales@auslig.gov.au

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Digital Map Data Products

Product	GDA Compliant
GEODATA COAST-100K	No COAST-100K data are currently available in AGD66 coordinates. Geoscience Australia is investigating the provision of both versions on both AGD66 and GDA94 coordinates.
GEODATA TOPO-250K Version 1	No The original TOPO-250K data are currently available on AGD66 coordinates. TOPO-250K Series 2 is being produced on GDA. Geoscience Australia is investigating the provision of both versions on both AGD66 and GDA94 coordinates.
GEODATA TOPO-250K Version 2	Yes
GEODATA TOPO-10M	Yes The difference between AGD66 and GDA94 coordinates is less than the accuracy of data at this scale. For all practical purposes, this product can be considered GDA compliant.
1:50 000 Topographic Data	Some Selected 1:50 000 scale data are currently GDA compliant however most 1:50 000 scale data tiles are based on AGD66 coordinates. All new 1:50 000 scale data will be GDA compliant subject to Australian Defence Force policies.
Topographic Base 100K Scale	No These data are currently available in AGD66 coordinates. Geoscience Australia is investigating methods of supplying this product in GDA94 coordinates. Only a limited amount of data at this scale will be revised in the near future.
Topographic Base 1M Scale	Yes For data derived at 1:1 million scale, the difference between AGD66 and GDA94 coordinates is negligible. For all practical purposes, this product can be considered GDA compliant.
RASTER-250K (Not geo-referenced)	No The map tiles supplied in the RASTER-250K product essentially have no datum as they have not been geo-referenced to any coordinate system. The images themselves are a reflection of the NATMAP 1:250 000 paper map products and hence contain a grid and graticule based on a particular datum. Currently most map images are based on AGD66 however as more 1:250 000 scale maps are revised, future versions of the product will contain more GDA based maps.
Australia Unfolded	No Australia Unfolded and Australia Unfolded 2 have coordinates based on AGD66 coordinates.
VMAP Level 0 (formerly Digital Chart of the World)	Yes VMAP Level 0 is based on WGS84 coordinates (which is essentially the same as GDA94 coordinates).

For further information please contact Geoscience Australia Data Sales: datasales@auslig.gov.au.

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DIGITAL ELEVATION MODEL (DEM) DATA

Product	GDA Compliant
GEODATA 9 SECOND DEM (Version 1)	No The current version of the GEODATA 9 Second DEM is based on AGD66 coordinates. Subsequent versions of the product will be provided on GDA.
Critical Aeronautical Heights	No Data are currently available in AGD66 coordinates. Geoscience Australia has no plans to convert this dataset to GDA94 coordinates unless there is significant user demand.
Eighteen Second Grid	No Data are currently available in AGD66 coordinates. Geoscience Australia is currently investigating methods for converting this dataset to GDA94 coordinates.
Three Second Grid	No Data are currently available in AGD66 coordinates. Geoscience Australia is currently investigating methods for converting this dataset to GDA94 coordinates.

For further information please contact Geoscience Australia Data Sales: datasales@auslig.gov.au.

ADMINISTRATIVE BOUNDARY DATA

Product	GDA Compliant
Australian Land Tenure	Yes Due to the scale of this product (1:4.7 million), the difference between AGD66 and GDA94 coordinates is negligible (less than the accuracy of the data). For all practical purposes, this product can be regarded as GDA compliant.
National Public and Aboriginal Lands	No Data are currently provided in AGD66 coordinates. Geoscience Australia will develop a strategy to migrate this dataset to GDA94 coordinates.
Aboriginal and Torres Strait Islander Commission (ATSIC) Boundaries	Yes At the scale of this product (generally 1:1 million), the difference between AGD66 and GDA94 is less than the accuracy of the data. For all practical purposes, this product can be regarded as GDA compliant.
Australia's River Basins	No Data are currently available in AGD66 coordinates. Geoscience Australia has no plans to convert this dataset to GDA94 coordinates unless there is significant user demand. Future new editions of the product may be available on GDA.
Register of the National Estate	No Data are currently available in AGD66 coordinates. Geoscience Australia has no plans to convert this dataset to GDA94 coordinates unless there is significant user demand. Future new editions of the product may be available on GDA.
Australian Postcode Boundaries	No Australian Postcode data are currently available in AGD66 coordinates. AUSLIG will investigate making this dataset available in GDA94 coordinates.
Commonwealth Electoral Boundaries	No Data are currently available in AGD66 coordinates. Geoscience Australia has no plans to convert the electoral boundaries from the 1992 and 1996 federal elections to GDA94 coordinates unless there is significant user demand. Future new editions of the product may be available on GDA.

Australian Maritime Boundaries

Product	GDA Compliant
Maritime Boundaries Map	Yes
Maritime Boundaries Digital Data	Yes

Data for Australian maritime boundaries already provides for GDA, as well as AGD, referenced products from the Australian Maritime Boundary Information System (AMBIS).

A major constraint on some maritime boundary coordinate information is imposed by international treaty arrangements with neighbouring countries. A number of treaties have been negotiated in terms of the AGD system and these coordinates cannot be changed other than by agreement of the parties. GDA coordinates can be computed from the agreed AGD system treaty coordinates, however these coordinates have no official status.

A similar situation applies to AGD system coordinates currently embodied in Commonwealth and State/Territory legislation. These coordinates are the official coordinates until such time as the legislation is amended.

As a result of these legal constraints, and the common need for maritime boundaries to coincide with existing maps and charts, AGD data will continue to be available.

Products relating to Australia's offshore territories, (for example Heard and MacDonald Islands and Australia's Antarctic Territory) will be computed, where required, in terms of a Geocentric Referencing System (compatible with GDA).

For further information please contact Geoscience Australia Data Sales: datasales@auslig.gov.au.

Resource and Environmental Data

Product	GDA Compliant
Minerals	Not Applicable
Vegetation: Pre-European Settlement (1788)	Not Applicable
Vegetation: Present (1988)	Not Applicable

Minerals
Vegetation: Pre-European Settlement (1788)
Vegetation: Present (1988)

Due to the scale of these products, the datum shift has a negligible effect. The difference between AGD66 and GDA94 coordinates is less than the accuracy of the data. For all practical purposes, these products can be regarded as GDA compliant.

For further information please contact Geoscience Australia Data Sales: datasales@auslig.gov.au.

Place Names Data

Product	GDA Compliant
Gazetteer of Australia	No The current version of the gazetteer is available on AGD66. The information contained in this product has been provided and compiled from a combination of Commonwealth, State and Territory agencies which are the custodians of the data. At this point, it is intended that any future releases of this product will be on GDA94 coordinates.
Map Sheet Names	Not Applicable

For further information please contact Geoscience Australia Data Sales: datasales@auslig.gov.au.

REMOTE SENSING DATA

Product	GDA Compliant
LANDSAT TM & MSS SPOT PAN & XS	Yes
ERS SAR RADARSAT JERS SAR	No See 1. below.

These data are available on WGS84 coordinates. The differences between WGS84 and GDA94 coordinates are significantly less than the accuracy of these data sets.

For further information contact ACRES Support staff wwwacres@auslig.gov.au.

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Geodetic Services

Product	GDA Compliant
National Geodetic Data Base (NGDB)	Yes The NGDB is a national archive of geodetic coordinates, with several types of coordinates kept for each site, as appropriate (e.g. GDA94, WGS84, AGD66, AGD84). This will be maintained to provide the historical integrity of the coordinates, to allow the generation of coordinate comparison reports and to assist with coordinate transformation. The NGDB also includes the AHD (Australian Height Datum) value for each site, but the AHD is not affected by GDA. The NGDB is therefore GDA compliant.
AUSGeoid	Yes AUSGeoid93 geoid-ellipsoid separation values are currently based on a geocentric datum (WGS84) which is for most practical purposes the same as GDA. A new geoid model (AUSGeoid98) is under development and will be computed in terms of GDA. AUSGeoid is therefore GDA compliant.

For further information please contact Geoscience Australia Geodesy: geodesy@auslig.gov.au.