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.

This research utilises metadata from GA's centralised metadata store containing the history of the equipment changes which have taken place at all GNSS stations; such as antenna or receiver swaps, firmware upgrades and removal/ alteration of antenna domes and cables. Several change detection algorithms have been implemented for automatic detection of discontinuities in the coordinate time series. Once offsets are detected, their position in time is correlated with equipment changes or earthquake occurrences nearby the station. If a correlation is found and the offset is visibly evident, the offset is introduced into a database. This information is used in the routine combination of weekly SINEX solutions using the CATREF software to produce an enhanced set of coordinates and velocities. It is shown that after cleansing the offsets in time series using this approach, the quality of the combined APREF solution is improved in terms of WRMS. By analysing time series coordinates at a few stations using CATS software, it is shown that the uncertainty of velocity estimates is improved after offsets are detected and removed from the time series.

AUSPOS, Geoscience Australia's online GPS positioning service, has now been in worldwide use since 2000 and has processed over 150,000 user data files. In 2011, the AUSPOS service was fully upgraded to use the Bernese Software as the processing engine together with more sophisticated GPS data analysis strategies, new ITRF to GDA transformations and the recently developed the AUSGEIOD09 model. In this presentation, we will briefly overview the AUSPOS2 system including the improved modelling and analysis strategies employed. Then, we will present test results for AUSPOS2 using 1, 2, 6, 12, 24 hours of data from 232 IGS2008 core stations as well stations from the Asia Pacific Reference Frame (APREF) network within mainland Australia using the IGS final, rapid and ultra rapid products, respectively. Preliminary tests using 24 hours data show that coordinate differences between AUSPOS solutions and APREF weekly solutions are within a millimetres level for all three components.

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.

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.

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 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 Mw=7.8 earthquake of 15 July, 2009 occurred along a section of the subduction zone south of New Zealand, where the Puysegur Block subducts beneath the Pacific Plate. The orientation of this subduction zone suggests that tsunamis generated along it pose a significant threat to the southeast coast of Australia, but since it had not experienced megathrust rupture until the 15 July event, the question of whether it was accumulating strain energy whose release could result in a large tsunami was open. We have used seismic, tsunami, geodetic and SAR data to study this earthquake and find that it involved primarily thrust motion on a fault plane dipping east at a shallow angle, consistent with expectations for a megathrust earthquake. The ability to use multiple data types to study this earthquake lead to improved ability to resolve parameters such as rupture velocity that are often difficult to constrain with seismic data alone. Seismic array data agree with rupture modelling of broadband waveforms in their prediction of a bilateral component to the earthquake rupture. Also, a tsunami of about 10 cm peak-to-peak amplitude was recorded by two tsunameter buoys in the Tasman Sea west of the epicenter, and we find that the tsunami travel times indicated by these data suggest the earthquake was characterised by a low rupture velocity of around 1 km/s. We will also present comparisons against GPS and InSAR data that further constrain parameters of the rupture. Finally, we will discuss the potential for earthquake activity further south along the Puysegur Trench, which poses a tsunami threat particularly to the eastern coast of Tasmania.

The combination of space geodetic techniques nowadays relies on the provision of accurate tie vectors locally measured on ground at geodetic co-location sites. Co-location of space geodetic sensors on-board of orbiting spacecraft (i.e. space co-locations) is an appealing solution to mitigate the shortcomings of terrestrial local ties, but their implementation in routine data processing is yet to be realised, and for now ground co-locations represent the only practical solution. Tie vectors directly enter and affect the computation of the global terrestrial reference frame, and as a consequence must be provided with an utmost level of accuracy. In addition, accurate tie vectors can be used to identify the presence of specific systematic errors affecting space geodetic techniques. In this presentation, we review the state-of-the-art in tie vector estimation and identify the factors that can degrade their accuracy as well as spotlighting common shortcomings present in the estimation process. Some of the issues we will discuss apply equally to co-locations of sensors in space and pertain to the level of accuracy currently achievable with the combination of space geodetic observations within GGOS.