Asia-Pacific Reference Frame (APREF)

Last updated:17 August 2023

The purpose of the Asia-Pacific Reference Frame (APREF) project is to create and maintain an accurate geodetic framework to meet the growing needs of industries, science programs and the general public using positioning applications in the Asia-Pacific region.

Background of APREF

The use of positioning technology is growing rapidly in industries such as mining, agriculture and construction. Furthermore, in recent years, there has been an increasing demand from emergency services, hazard modellers, and land, utility and asset managers. The applications of these users have a demonstrated need for centimetre level or better geodetic infrastructure. In order to provide this, the Asia-Pacific region needs a consistent, continually refined and easily accessible reference frame.

In the Asia-Pacific region there are a substantial number of state-of-the-art Global Navigation Satellite System (GNSS) networks, which are commonly operated by national mapping agencies or private sector organisations. These networks represent an important and significant investment by the respective governments and industry in their own spatial infrastructure. However, when the Asia-Pacific region is viewed as a whole:

  • the infrastructure is comparatively sparse, inaccurate, and difficult to access when compared to other parts of the world such as Europe and the Americas
  • in general, the networks are not linked together, or to the global reference frame
  • the lack of data sharing impacts on the accuracy and type of geodetic analysis that can be performed.

It has become increasingly clear that the Asia-Pacific regional geodetic reference frame (crudely constructed as a patchwork of national and regional datums) is below the standard that it now available (and expected) in other regions, such as Europe and the Americas. As a consequence, this can be detrimental to regional scientific studies and national geodesy, leading to a loss in competitive advantage by nations in the Asia-Pacific region.

Recognising the importance of improving the regional geodetic framework, member countries of the 18th United Nations Regional Cartographic Conference for Asia and the Pacific (UNRCC-AP; October 2009, Bangkok), agreed to improve the reference frame in the Asia-Pacific region. APREF has already made some progress in developing the Asia-Pacific regional geodetic infrastructure; however, it can still be characterised as being a work in progress. APREF is a voluntary, collegial, non-commercial endeavour, and there is no central funding source, and participating organisations contribute their own resources.

Objectives of APREF

The broad objective of APREF is to create and maintain a densely realised and accurate geodetic framework, based on continuous observation and analysis of GNSS data. APREF addresses issues associated with the definition, realisation and maintenance of the Asia-Pacific Reference Frame.

In the short-term, the APREF project:

  • will encourage sharing of GNSS data from Continuously Operating Reference Stations (CORS) in the region
  • develop an authoritative source of coordinates, and their respective velocities, for geodetic stations in the Asia-Pacific region.

In the longer term, the APREF project:

  • will develop and maintain the APREF Permanent CORS Network, in close cooperation with International GNSS Service (IGS)
  • improve the contribution of APREF sites to the International Terrestrial Reference Frame (ITRF)
  • provide more infrastructure to support geodetic projects
  • establish a dense velocity field model in Asia and the Pacific for scientific applications and the long-term maintenance of the Asia-Pacific reference frame
  • organise regular symposia addressing activities carried out at national and regional levels related to the work and objectives of APREF.

APREF organisational structure

The APREF project consists of:

  • Central Bureau
  • Network operators
  • Data centres
  • Analysis centres.

The Central Bureau, within Geoscience Australia, functions as the 'day-to-day' APREF coordinating body. Specifically, the Central Bureau ensures that APREF products are made available to the global geodetic community. Furthermore, they are the combination centre responsible for analysing, combining and validating the individual solutions of the contributing Analysis Centres, and for expressing the combined solution in the ITRF. The APREF project already has three Local Analysis Centres (LACs): Geoscience Australia, Office of Surveyor-General Victoria, Australia, and the Institute of Geodesy and Geophysics, Chinese Academy of Sciences.

Participating agencies

In response to the March 2010 Call for Participation, a large number of agencies have agreed to participate in APREF, Table 1 summarises their commitments.

Country/Locality Responding Agency Proposed Contribution
Analysis Archive Stations
Afghanistan National Geodetic Survey (USA)   2
Alaska, USA National Geodetic Survey (USA)   7
American Samoa National Geodetic Survey (USA)   1
Australia Geoscience Australia 139
Australia Curtin University  1
Australia Department of Natural Resources, Mines and Energy, QLD   8
Australia Department of Environment, Land, Water and Planning  107
Australia Department of Infrastructure, Planning and Logistics, Northern Territory   5
Australia Department of Primary Industries, Parks, Water & Environment, Tasmania   2
Australia Department of Finance, Services & Innovation, New South Wales   170
Australia RTK NetWest   12
Australia IPS Radio and Space Services   3
Australia Department of Transport and Main Road, Queensland   17
Brunei Survey Department, Negara Brunei Darussalam   1
China The Institute of Geodesy and Geophysics, Chinese Academy of Sciences   
Cook Islands Geoscience Australia and Lands Department of Cook Islands  1
Cook Islands Geospatial Information Authority of Japan   1
Federated States of Micronesia Geoscience Australia and Weather Service of the Federated States of Micronesia  1
Fiji Geoscience Australia and Lands Department of Fiji  1
French Polynesia Geospatial Information Authority of Japan   1
Guam, USA National Geodetic Survey (USA)   1
Hong Kong, China Survey and Mapping Office   14
Indonesia Bakosurtanal   4
Iran National Cartographic Center, Iran   6
Iraq National Geodetic Survey (USA)   6
Japan Geospatial Information Authority of Japan  10
Kazakhstan Kazakhstan Gharysh Sapary   2
Kiribati Geoscience Australia and Weather Service of Kiribati  1
Kiribati Geospatial Information Authority of Japan   2
Macau, China Macao Cartography and Cadastre Bureau   3
Marshall Islands Geoscience Australia and Weather Service of Marshall Islands  1
Malaysia Department of Survey and Mapping Malaysia, JUPEM   7
Mongolia Administration of Land Affairs, Construction, Geodesy and Cartography (ALACGaC)   8
Nauru Geoscience Australia and Lands Department of Nauru  1
New Zealand Land Information New Zealand 38
Northern Mariana Islands National Geodetic Survey (USA)   1
Papua New Guinea National Mapping Bureau, Papua New Guinea, and Geoscience Australia   2
Philippines Department of Environment and Natural Resources, National Mapping and Resource Information Authority 4
Samoa Geoscience Australia and Lands Department of Samoa  1
Solomon Islands Geoscience Australia and Weather Service of Solomon Islands  1
Tonga Geoscience Australia and Lands Department of Tonga  1
Tuvalu Geoscience Australia and Weather Service of Tuvalu  1
Vanuatu Geoscience Australia and Lands Department of Vanuatu  1

Data and products

APREF data and products contributed to and generated by the APREF project are provided with an open access data policy via the internet following the practice of the IGS.

How can I participate in APREF?

APREF encourages participation from organisations active in the Asia-Pacific region who are prepared to, on an ongoing basis (at least two years):

  • provide GNSS data from CORS Stations
  • provide access and on-line archiving of APREF data and products for users; and/or
  • routinely analyse some, or all, of the APREF GNSS CORS data, providing station coordinate estimates.

To participate in APREF, the responding agencies should write a Letter of Intent to

APREF Central Bureau
Dr John Dawson
National Positioning Infrastructure Branch
Geoscience Australia
GPO Box 378 Canberra ACT 2601 Australia

Telephone: +61 2 6249 9028
Fax: +61 2 6249 9969

This Letter of Intent should include the following information:

  • organisation name and address
  • name, address and contact details of the primary and secondary points of contact within the contributing organisation
  • specific details of the organisation's proposed contribution to APREF.

Station and data standards

If possible, APREF stations should meet the standards of the International GNSS Service (IGS).

Critically, each station operator must ensure that the contributed stations will operate for at least two years. Furthermore, station metadata, such as receiver and antenna information, is a mandatory requirement for participation in the APREF project.

All GNSS data should be made available in RINEX format at a 30-second sampling rate and where available, participants may also submit broadcast ephemeris and meteorological RINEX files. Contributions of Regional Navigation Satellite Systems (RNSS) data are also most welcome. See Procedures for becoming an APREF station for further details.

Analysis standards

For those organisations wanting to contribute solutions, the analysis must be to the standard consistent with the IERS Conventions 2010 (for example using the Bernese, GIPSY, GAMIT, NAPEOS, EPOS, PAGES software packages). For further details see IERS Conventions Center.

Contributed solutions are in the SINEX format.

APREF mandate

APREF was mandated by Resolution 1 (Regional Geodesy) of the 18th United Nations Regional Cartographic Conference (UNRCC) for Asia and the Pacific, 26 - 29 October 2009, Bangkok, Thailand. APREF is also endorsed by the: International GNSS Service (IGS), United Nations Office for Outer Space Affairs (UNOOSA), and the Federation of International Surveyors (FIG).