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Surveyor-General Victoria and the Geological Survey of Victoria, part of the Department of Jobs Precincts and Regions (DJPR), are collaborating with Geoscience Australia (GA) to capture airborne gravity data throughout 2021/2022 across southeast Victoria.
The objective of the project is to collect consistent and evenly distributed gravity measurements.
The new gravity data will significantly improve Victoria’s gravity model and the accuracy of real-world heights from GPS positioning.
The data will also be used by geoscientists to further understand southeast Australia’s geological "architecture" and how it has evolved over time.
Gravity surveys in Victoria
Victoria has some of the best coverage of ground gravity data in Australia, but some areas such as the alpine, coastal and desert regions are difficult to access. This limits gravity data coverage, with corresponding local uncertainty in the gravity model.
The surveys will cover approximately 100,000 square kilometres, including the Victorian coast from Cape Otway to Cape Howe, metropolitan Melbourne and the Australian Alps.
The airborne gravity survey will deliver consistent and evenly distributed gravity measurements across these areas, with minimal disturbance to land users and the environment.
The survey will involve flights over diverse land types, including:
- urban and rural areas
- mountainous and coastal terrain
- national and state parks and reserves
Airborne gravity surveys have been safely and successfully completed across coastal Gippsland (2011), southwest Victoria (2019) and near Bendigo (2004, 2019).
Flight operations and the impact on the environment
The airborne gravity surveys are being flown throughout 2021/2022 and will take several months to complete.
The airborne gravity survey will be performed in stages. Stakeholders and the public will be notified at least two weeks before operations start across regions.
The survey operations will be conducted by Sander Geophysical Limited. Experienced pilots operating a DHC-6 Twin Otter and Cessna Caravan fixed wing aircraft will fly along a planned route with flight lines spaced 500 metres to 1 km apart.
The aircraft will fly in public airspace at a nominated ground clearance of 150 metres, increasing to 300 metres over built-up areas.
An independent air safety audit has been conducted on the aircraft and flight plans. Flying will only occur in favourable weather conditions.
The DHC-6 Twin Otter and Cessna Caravan are a standard aircraft with scientific instruments on board. Noise levels on the ground will be transient and less than the sound of a passing motorbike.
Specialised gravity-sensing instrumentation will be used to measure extremely small variations in the earth’s natural gravitational pull. The gravity instruments are passive and do not emit any signals, or impact people, animals or infrastructure.
The data and gravity model will improve height determination from GPS positioning to an accuracy of a few centimetres. The changes will support productive and effective land management and technological innovation, and meet community expectations of reliable GPS positioning in Victoria.
The new data will advance the geoscience that assists the Victorian Government to manage its earth resources, infrastructure and natural hazards. It will also assist the state’s resources sector, which contributes to regional jobs and economic growth.
The gravity data will be freely available through the Victorian Government’s open data platforms and licensed for public use. The data will also be included in the national geoscience database and data portals managed by Geoscience Australia.
Page last updated: 21/09/21