In 1994, the United Nations Regional Cartographic Conference for Asia and the Pacific resolved to establish a Permanent Committee comprising of national surveying and mapping agencies to address the concept of establishing a common geographic information infrastructure for the region. This resolution subsequently led to the establishment of the Permanent Committee for GIS Infrastructure for the Asia and Pacific (PCGIAP). One of the goals of the PCGIAP was to establish and maintain a precise understanding of the relationship between permanent geodetic stations across the region. To this end, campaign-style geodetic-GPS observations, coordinated by Geoscience Australia, have been undertaken throughout the region since 1997. In this presentation, we discuss the development of an Asia Pacific regional reference frame based on the PCGIAP GPS campaign data, which now includes data from 417 non-IGS GPS stations and provides long term crustal deformation estimates for over 200 GPS stations throughout the region. We overview and evaluate: our combination strategy with particular emphasis on the alignment of the solution onto the International Terrestrial Reference Frame (ITRF); the sensitivity of the solution to reference frame site selection; the treatment of regional co-seismic and post-seismic deformation; and the Asia-Pacific contribution to the International Association of Geodesy (IAG) Working Group on "Regional Dense Velocity Fields". The level of consistency of the coordinate estimates with respect to ITRF2005 is 6, 5, 15 mm, in the east, north and up components, respectively, while the velocity estimates are consistent at 2, 2, 6 mm/yr in the east, north and up components, respectively.

Applications dated 18 August 2010 for verification of a reference standard of measurement under Regulation 12 of the National Measurement Regulations 1999 was received from the Land and Property Management Authority, NSW for verification of GDA94 position on their CORSnet monuments. This report documents the processing and analysis of GPS data observed by the CORSnet-NSW GPS stations during a 7-day period from 08 August to 14 August 2010 (day of year 220 to 226) for 4 stations (CSNO, IHOE, PBOT, and TBOB) to satisfy the position verification requirements.

The IAG Working Group (WG) 'Integration of Dense Velocity Fields in the ITRF' was created in 2011 as follow-up of the WG 'Regional Dense Velocity Fields' (2007-2011). The goal of the WG group is to densify the ITRF (International Terrestrial Reference Frame) using regional GNSS solutions as well as global solutions. This was originally done by combining several cumulative position/velocity solutions as well as their residual position time series submitted to the WG by the IAG regional reference frame sub-commissions (APREF, EUREF, SIRGAS, NAREF) and global (ULR) analysis centers. However, several test combinations together with the comparison of the residual position time series demonstrated the limitations of this approach. In June 2012, the WG decided to adopt a new approach based on a weekly combination of the GNSS solutions. This new approach will mitigate network effects, have a full control over the discontinuities and the velocity constraints, manage the different data span and derive residual position time series in addition to a velocity field. All initial contributors have agreed to submit weekly solutions and in addition initial contacts have been made with other sub-commissions particularly Africa in order to extent the densified velocity field to all continents. More details on the WG are available from http://epncb.oma.be/IAG/.

Advice to National Measurement Institute regarding update to the recognized-value standard of measurement for position, June 2011

The national geodetic program in Australia is undertaken by the National Geospatial Reference System (NGRS) Section within Geoscience Australia. The NGRS is a continually evolving system of infrastructure implemented through the existing geodetic techniques such as Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS) and Very Long Baseline Interferometry (VLBI). The NGRS serves the broader community by providing an accurate foundation for positioning, and consequently all spatial data, against which every position in Australia is measured and can be legally traced. In Australia, the sparsity of geodetic infrastructure has limited the developments of geodetic applications. For instance, the Geocentric Datum of Australia 1994 (GDA94) was based on observations (1992 - 1994) from a sparse network of Continuously Operating Reference Station (CORS) called the Australian Fiducial Network (AFN). Since that time the demand for higher accuracies has resulted in GDA94 no longer adequately serving user demand. The adoption of a fully dynamic datum will ensure that Australians can use positioning technology to its fullest capability, whereas at present when using GDA94 they are limited to the accuracy that was achievable in 1994 when GDA94 was created. Consequently, national infrastructure development programs, such as AuScope, have been implemented to improve the geodetic accuracies by contributing to the next generation of the Global Geodetic Observing System (GGOS). This presentation reviews the national geodetic activities in Australia, especially the AuScope program, a recent enhancement to the Australian geodetic infrastructure.

The gravitational attraction of the Galactic centre leads to the centrifugial acceleration of the Solar system barycentre. It results in secular aberration drift which displaces the position of the distant radio sources. The effect should be accounted for in high-precision astrometric reductions as well as by the corresponding update of the ICRS definition.

Ongoing developments in geodetic positioning towards greater accuracies with lower latency are now allowing the measurement of the dynamics of the Earth's crust in near real time. However, in the Australian circumstance a sparsity of geodetic infrastructure has limited the application of modern, geodetic science to broader geoscience research programs. Recent enhancements to the Australian geodetic infrastructure, through the AuScope initiative, offer opportunities for research into refinement of geodetic accuracies, as well as their application to measuring crustal deformation.

The annual Asia Pacific Regional Geodetic Project (APRGP) GPS campaigns are an important activity of the regional geodesy working group of the Permanent Committee on GIS Infrastructure for Asia and the Pacific Region (PCGIAP). The major objective of these campaigns is the densification of the International Terrestrial Reference Frame (ITRF) in the Asia-Pacific region. The APRGP GPS campaigns consist of 7-day observation sessions and have been undertaken from 1997 to 2008. In this work, we focus on the assessment of realistic uncertainty estimates of the derived crustal velocities, which is still an important unresolved issue. Although assessments of the quality of Continuous GPS (CGPS) determinations of crustal velocity have previously been undertaken, little research has been conducted on the quality of the velocity estimates derived from campaign-based coordinate time series. We have compared our velocity estimates with those published by the International GNSS service (IGS) at common sites and found that they are consistent at 1.4, 1.7, 3.9 mm/yr level in the east, north and up components, respectively. Also, we find that a minimum of 3 years of campaign data is required before reliable velocity estimates can be derived from campaign-based GPS, which is mostly due to the increased possibility of outliers.

Australia's National Geospatial Reference System (NGRS) is a continually evolving system of infrastructure, data, software and knowledge. The NGRS serves the broader community by providing an accurate foundation for positioning, and consequently all spatial data. The NGRS is administered by the Intergovernmental Committee on Surveying and Mapping (ICSM) and maintained by its Federal and State jurisdictions. Increasingly, the role of Global Navigation Satellite Systems (GNSS) in positioning has required the globalisation of national coordinate systems. In the early 1990's ICSM endorsed the adoption of the Geocentric Datum of Australia (GDA94) which was aligned to the International Terrestrial Reference Frame (ITRF) with a stated uncertainty of 30mm horizontally and 50mm vertically. Since that time crustal deformation and the demand for higher accuracies has resulted in GDA94 no longer adequately serving user requirements. ITRF has continued to evolve in accuracy and distribution to the extent that it now requires very accurate modelling of linear and non-linear crustal deformation. Even the Australia plate, which has long been considered to be rigid, is now considered to be deforming at levels detectable by modern geodesy. Consequently, infrastructure development programs such as AuScope have been implemented to ensure that crustal deformation can be better measured. The Auscope program also aims to improve the accuracy of the ITRF by contributing to the next generation of the Global Geodetic Observing System in our region. This approach will ensure that the ITRF continues to evolve and that Australia's NGRS is integrally connected to it with equivalent accuracies. Ultimately this will remove the need for National Reference Systems, with a globally homogenous and stable reference system (e.g., ITRF) being far more beneficial to society. This paper reviews Australia's contribution to GGOS and how this impacts on positioning in Australia.

The individual apparant motion of distant radio sources is supposed to be caused by the effect of intrinsic structure variations of the active galactic nuclei (AGN) and not correlated over the sky. However, some models of the expanded Universe predict that systematic astrometric proper motion of distant radio sources do not vanish as radial distance from observer to the source grows. These systematic effects can even increase with the distance making possible to measure them with high-precision astrometric techniques like VLBI. The Galactocentric acceleration of the Solar system barycentre might cause a secular aberration drift with magnitude 4 microarcsec/year. Also the Solar system motion relative to the cosmic microwave background produces additional dipole effect, dependent on red shift. We analyzed a large set of geodetic VLBI data spanning from 1979 till 2008 to estimate the dipole, the rotational, and the quadrupole harmonics in the expansion of the vector field of the proper motions of quasars in the sky. The dipole and quadrupole vector spherical harmonics from the individual apparent motion of 687 radio sources were estimated. In addition, the estimates have been obtained separately for different red shift zones. We show that for the next decade the geodetic VLBI technique might approach to the level of accuracy to test the cosmological models of the Universe. It is important to organise a dedicated observational program to increase the number of measured proper motion to ~3000.