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/.

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.

Australia is a large continent with a relatively low population which is highly dependent on the mining, agricultural and transport industries for economic prosperity. These industries are themselves increasingly dependent on having access to high-quality geodetic infrastructure, especially when seeking operating efficiencies. Australia is also surrounded to the north and east by some of the most seismically active zones in the world, and is geographically isolated by the Indian, Pacific and Southern Oceans. This combination of characteristics creates some interesting challenges for the Australian Government in maintaining, developing and delivering a stable reference frame as a platform upon which a precise positioning capability can be established for science and society more generally. This presentation will detail recent GGOS related efforts in Australia to improve the accuracy of the International Terrestrial Reference Frame (ITRF). It will also discuss crustal deformation monitoring programs that allow ITRF based precise positioning services to be used in areas where localized deformation is not detected by existing GGOS infrastructure. Lastly, the presentation will also summarise efforts currently underway to enhance the provision of access to the ITRF anywhere, anytime across the Australian landmass in real time.

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.

In a collaborative effort with the regional sub-commissions within IAG sub-commission 1.3 'Regional Reference Frames', the IAG Working Group (WG) on 'Regional Dense Velocity Fields' (see http://epncb.oma.be/IAG) has made a first attempt to create a dense global velocity field. GNSS-based velocity solutions for more than 6000 continuous and episodic GNSS tracking stations, were proposed to the WG in reply to the first call for participation issued in November 2008. The combination of a part of these solutions was done in a two-step approach: first at the regional level, and secondly at the global level. Comparisons between different velocity solutions show an RMS agreement between 0.3 mm/yr and 0.5 mm/yr resp. for the horizontal and vertical velocities. In some cases, significant disagreements between the velocities of some of the networks are seen, but these are primarily caused by the inconsistent handling of discontinuity epochs and solution numbers. In the future, the WG will re-visit the procedures in order to develop a combination process that is efficient, automated, transparent, and not more complex than it needs to be.

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 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.

This report refers to the 5th Local Monitoring Survey completed at the Pohnpei (POHN) continuous GPS (CGPS) station on Saturday 15 August 2009

The purpose of this paper is to investigate and quantify the accuracy with which hydrological signals in the Murray-Darling Basin, southeast Australia can be estimated from GRACE. We assessed the extent to which the Earth's major geophysical processes contaminate the gravitational signals in the Basin. Eighteen of the world's largest geophysical processes which generate major gravitational signals (e.g. melting of the Greenland icesheet, hydrology in the Amazon Basin) were simulated and the proportion of the simulated signal detected in the Murray - Darling Basin was calculated. The sum of the cumulative effects revealed a maximum of ~4 mm (equivalent water height) of spurious signal was detected within the Murray - Darling Basin; a magnitude smaller than the uncertainty of the basin-scale estimates of changes in total water storage. Thus, GRACE products can be used to monitor broad scale hydrologic trends and variability in the Murray-Darling Basin without the need to account for contamination of the estimates from external geophysical sources.

The new Australian geodetic VLBI network operated by University of Tasmania (UTAS) started regular observations in October, 2010. Three 12-meter "Patriot" radio telescopes are focused on improvement of the celestial and terrestrial reference frames in the southern hemisphere. We present first results from analysis of an eight-month set of geodetic VLBI data.