<div>The integrity and strength of multi-technique terrestrial reference frames, such as realisations of the International Terrestrial Reference Frame (ITRF), depend on the precisely measured and expressed local-tie connections between space geodetic observing systems at co-located observatories. Australia has several observatories which together host the full variety of space geodetic observation techniques, including Global Navigation Satellites Systems (GNSS), Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) beacons.</div><div><br></div><div>This report documents the technical aspects of the local tie survey completed at the Mount Stromlo observatory, in Canberra in September 2018. The aim of the survey was to precisely measure the local terrestrial connections between the space-based geodetic observing systems co-located at the observatory, which include 3 International GNSS Service (IGS) stations (AU45&nbsp;A 50119M001, STR3&nbsp;A 50119M005 & STR1&nbsp;A 50119M002), SLR (7825&nbsp;A 50119S003) and DORIS (MSPB&nbsp;A 50119S004) infrastructure. </div><div><br></div><div>In particular, this report documents the indirect measurement of the SLR invariant reference point. Geoscience Australia has routinely performed classical terrestrial surveys at Mount Stromlo, including surveys in 1999, 2002 and 2003 (post-fire). A high precision survey was conducted between the survey pillars surrounding the SLR observatory. These survey pillars were monitored to ensure their stability as part of a consistent, stable terrestrial network from which local tie connections were made to the SLR and other observing systems. The relationship between points of interest included the millimetre level accurate connections and their associated variance covariance matrix.</div><div><br></div>

<div>The integrity and strengths of multi-technique terrestrial reference frames such as ITRF2020 depend on the precisely measured and expressed local tie connections between space geodetic observing systems at co-located observatories. A local tie survey was conducted at the Mount Pleasant Geodetic observatory, in Hobart in March 2023. The aim of the survey was to precisely measure the local terrestrial connections between the space-based geodetic observing systems co-located at the observatory, which includes a permanent International GNSS Service (IGS) site (HOB2&nbsp;A 50116M004), and Very Long Baseline Interferometry (VLBI) radio telescopes. In particular, this report documents the indirect measurement of the VLBI invariant reference point for both the 12m (7374&nbsp;A 50116S007) and 26m (7242 A 50116S002) radio telescopes at the site. Geoscience Australia has routinely performed classical terrestrial surveys at Mount Pleasant since 1995. A high precision survey was conducted between the survey pillars surrounding the observatory. These survey pillars were monitored to ensure their stability as part of a consistent, stable terrestrial network from which local tie connections were made to the VLBI and GNSS systems. The relationship between points of interest included the millimetre level accurate connections and their associated variance covariance matrix.</div><div><br></div>

<div>The integrity and strength of multi-technique terrestrial reference frames, such as realisations of the International Terrestrial Reference Frame (ITRF), depend on the precisely measured and expressed local-tie connections between space geodetic observing systems at co-located observatories. Australia has several observatories which together host the full variety of space geodetic observation techniques, including Global Navigation Satellites Systems (GNSS), Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) beacons.</div><div><br></div><div>This report documents the technical aspects of the local tie survey completed at the Mount Stromlo observatory, in Canberra in 2014. The aim of the survey was to precisely measure the local terrestrial connections between the space-based geodetic observing systems co-located at the observatory, which include 3 International GNSS Service (IGS) stations, SLR and DORIS infrastructure. In particular, this report documents the indirect measurement of the SLR invariant reference point. Geoscience Australia has routinely performed classical terrestrial surveys at Mount Stromlo, including surveys in 1999, 2002 and 2003 (post-fire). A high precision survey was conducted between the survey pillars surrounding the SLR observatory. These survey pillars were monitored to ensure their stability as part of a consistent, stable terrestrial network from which local tie connections were made to the SLR and other observing systems. The relationship between points of interest included the millimetre level accurate connections and their associated variance covariance matrix.</div><div><br></div>

<div>The Ramu-Markham Fault (RMF) runs along the northern edge of the Markham Valley in eastern Papua New Guinea’s Morobe Province. It is the active plate boundary between the South Bismarck Plate and&nbsp;the New Guinea Highlands/Papuan Peninsula Blocks, and is thought to accommodate about 4 cm/yr of convergence associated with the Finisterre arc-continent collision. Because Papua New Guinea’s recently published national seismic hazard map revealed a potential vulnerability of its 2nd largest city, Lae, to RMF earthquakes, Lae has become the focus of a seismic risk study. One of the aims of this study is to improve the characterisation of the earthquake potential along the RMF, and for this reason a new Global Navigation Satellite System (GNSS) campaign has been undertaken to re-survey over 70 existing benchmarks in and around Morobe Province, including about 35 benchmarks in and around the city of Lae itself. The vast majority of these benchmarks have now been surveyed, and in this paper we discuss the survey and a preliminary analysis of the data.</div><div><br></div>Presented at the 2023 Australian Earthquake Engineering Society (AEES) Conference