Enhancing NSW statewide geophysics with high resolution company data

Matthews, Sam1

1Geological Survey of New South Wales, Department of Regional NSW, Maitland, NSW, Australia

The Geological Survey of New South Wales (GSNSW) has released an updated suite of magnetic grids and imagery which improve the existing images through the inclusion of high-resolution, open-file company data. The foundation of this product comprises over 60 regional government surveys flown at 200 to 400 m line-spacings. The addition of about 150 private company surveys flown at 50 to 200 m line-spacings increases the resolution of the grids in these areas. The higher-resolution surveys also allow the data to be gridded with a 25 m cell size rather than the previous 50 m, which provides better definition of anomalies.

The project commenced with the quality assurance (QA) of about 650 airborne magnetic surveys flown in New South Wales since the late 1950s. An algorithm was derived to quantitatively assess each survey on the merits of the survey metadata. The algorithm applied a weighted score to various parameters such as line-spacing, flight height, sampling interval, and survey area. A baseline score was calculated for the previous statewide merge based on the regional government surveys, which became the cut-off for the company data. All surveys falling below that score were excluded. A final manual QA of the remaining surveys was performed to ensure only the best data filtered through the algorithm before being included in the new merges.

The boundaries of each survey were placed into a shapefile and where any overlap occurred, the survey with the lower score from the algorithm was clipped using the boundaries of the higher scoring survey. An external buffer of 500 m was added to the survey boundaries, creating a small overlap to allow the software to align features when merging. After clipping, all surveys were re-sampled and re-projected into a unified grid cell size and projection. A base layer of total magnetic intensity (TMI) for the merge was created using the regional government surveys, which were levelled to the Australia-wide 70 km spaced magnetic traverses (AWAGS) to retain the long spatial wavelengths. Holes were clipped into this grid and buffered to the shapes of the company surveys. The final merge with the company data was then performed to create the high resolution statewide TMI grid.

The TMI grid became the foundation to create a series of enhancements. Reduction to the Pole, First and Second Vertical Derivative, and Tilt Angle filters were applied to the TMI data, which were then reprojected into a suite of projections relevant for NSW. The final high-resolution imagery is now available on MinView, the GSNSW web-based data portal. The improvements are immediately visible, with far higher resolution of magnetic anomalies across the state, especially in regions with extensive company surveys. The additional resolution provides precise definition of geophysical signatures and geological structures at all scales and will lead to improved image interpretation for geological mapping and exploration targeting.


Biography

Sam Matthews works as a geophysicist within the Geological Survey of NSW. He earnt his PhD from Macquarie University studying the geophysical signatures of sequestered CO2 and is now responsible for maintaining and enhancing all geophysical data within NSW.

How the GSNSW is helping to preserve data from the NSW infrastructure boom

Adewuyi, David1

1Geological Survey of New South Wales, Department of Regional NSW, Maitland, Australia

Geotechnical data provide information about rock/soil characterisation, strength and stability and subsurface hazard identification that is critical to infrastructure planning, design and construction, and asset protection and maintenance. These data also provide information about the volume and quality of construction materials that, when enough data is collated, can be used to assess available resources for possible extraction. Due to the vast recent and forecast increase in public construction infrastructure spending, including a New South Wales (NSW) Government commitment of $93 billion over four years to 2022–23, responsible NSW agencies that procure geotechnical services have been tasked with maintaining the integrity of their geotechnical data assets. Keeping a corporate record of geotechnical reports and re-using the information has been a key challenge for these agencies.

In January 2020, the NSW Department of Planning, Industry and Environment (including the Geological Survey of NSW (GSNSW), Sydney Water and Public Works Advisory NSW) signed a Memorandum of Understanding (MoU) with Transport for New South Wales (comprising Sydney Metro, Sydney Trains, and Roads and Maritime Services) and the Australian Rail Track Corporation, to collaborate in the development of a whole-of-government single repository for NSW geotechnical information – the Government Geotechnical Report Database (GGRD). Presently, there are over 3450 Public Works reports available in the GSNSW’s DiGS document archive and geo-located in the online spatial viewer, MinView. Industry professionals in both the private and public sector have attested to the usefulness of the database in the initial planning stages of projects for informing desktop studies, gaining preliminary understanding of subsurface conditions and identifying potential risks while scoping geotechnical investigations, which enables a more robust estimation of project costs.

To demonstrate how the geotechnical data can be used, GSNSW is working on the construction of a 3D geotechnical model as a proof-of-concept planning tool for the Western Sydney Aerotropolis area. As well as modelling the strength of the subsurface, the project will also give insights on the extraction potential of construction resources in the area.

The GGRD will also support the ongoing digital transformation in NSW that is being applied in the creation of a NSW Spatial Digital Twin, launched by NSW Spatial Services in early 2020. The NSW Spatial Digital Twin will provide 3D and 4D digital spatial models of built and natural environments. It allows visualisation of amenities even before construction begins to enable better planning of infrastructure and communities in the state.


Biography

David Adewuyi is a Senior Geoscientist Special Projects in the Geoscience Information unit of the Geological Survey of New South Wales (GSNSW), where he manages the Government Geotechnical Reports Database (GGRD) project. The GGRD is a whole of government single repository for government procured geotechnical reports and data.

Mapping the geology that matters – the role of Australia’s geological surveys in supporting mineral discovery in the 21st century

Yeats, Chris1

1Geological Survey of New South Wales, Department of Regional NSW, Maitland, Australia

During the late 20th century, Australia’s geological survey organisations (GSOs) completed 1:250,000 scale surface geological mapping of the continent. This work provided a framework for mineral exploration that led to the discovery of most of the surface and near-surface deposits in areas of outcropping basement that form the basis of the country’s current mineral production. From the 1970s, geological mapping was augmented by regional geophysical data and from the mid-1990s increased geochronological analysis, which supported a second generation of higher resolution mapping under the National Geoscience Mapping Accord into the early 21st century. However, this second wave of mapping, which often focused on areas of good quality outcrop with known mineral potential, did not lead to many significant discoveries and over 80% of the country’s current mineral production now comes from deposits discovered prior to 1980.

In order to provide a framework for mineral discovery in the 21st century, Australian GSOs need to change the search space and provide the exploration industry with the data they need to successfully explore deeper and step out into the 75% of the Australian continent where prospective basement is buried under younger, non-prospective cover. Essentially, GSOs must map “the geology that matters” – defining the structural architecture, temporal evolution and lithologies of potentially prospective geological terranes, regardless of whether they are exposed at the surface, or not.

This work has already started in New South Wales (NSW), with the NSW Seamless Geology providing an interpreted lithotectonic framework for the state, based primarily on surface mapping and potential field geophysical data. However, further geological data is required to support this model, particularly in undercover terranes. As participants in the ten-year MinEx CRC National Drilling Initiative (NDI), Australia’s GSOs will generate new precompetitive geoscientific data over several underexplored, undercover regions across the continent. Equally importantly, the NDI will support development of cheaper, faster drilling technologies, real-time sensing technologies and new concepts and decision-making tools that will aid mineral exploration in deep and/or covered terranes, thereby making large parts of the continent more accessible to mineral exploration.

Concurrently, Australia’s GSOs are deploying new technologies to augment existing national datasets. The ~55km-spaced stations of the collaborative Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) is delivering a lithospheric-scale conductivity model that can be used to define areas of anomalous fluid flow for further investigation. Completion of the AusAEM electromagnetic survey across Australia over the next four years will deliver a near-surface conductivity model that can be used to define depth to basement, as well as potential for mineral and groundwater resources. New geochemical and isotopic datasets are also being used to define fluid sources and crustal evolution at a continental scale.

As we enter the third decade of the 21st century, Australia’s GSOs face a watershed moment. We must and are transitioning from mapping the surface geology, to mapping prospective geology and delivering new types of data, to create a framework for the discovery of the new deposits needed to support Australia’s mineral industry into the second half of the century.


Biography

Chris was Executive Director of the Geological Survey of NSW from June 2015 to December 2020. Prior to this, he spent 17 years as a researcher and manager at CSIRO, where his work focussed on the formation of and exploration for gold and base metal deposits in ancient and modern terranes.

About the GSA

The Geological Society of Australia was established as a non-profit organisation in 1952 to promote, advance and support Earth sciences in Australia.

As a broadly based professional society that aims to represent all Earth Science disciplines, the GSA attracts a wide diversity of members working in a similarly broad range of industries.