Case study Sentinel-2 reveals the barest Earth
Published:10 March 2022
Published:10 March 2022
Satellite imagery can provide useful data for mapping surface mineralogy and geochemistry of soil and rock. However, exposed rock and soil are often masked by vegetation.
In 2019, researchers developed an algorithm to preferentially weight bare earth pixels from Landsat satellite images through time. This work produced a national scale Barest Earth mosaic of the Australian continent with significantly reduced seasonal vegetation cover, to support enhanced mapping of soil and geology.
This release takes advantage of improvements made since 2019 version and uses images from Sentinel-2 satellite observations, up to September 2020.
A snapshot of regular satellite imagery on the left and Sentinel-2 Barest Earth imagery on the right
Sentinel-2 is part of the European Earth Observation program, with 2 polar-orbiting satellites: Sentinel-2A, launched in 2015, and Sentinel-2B, launched in 2017. The twin satellites provide shorter revisit times, increasing the frequency of observations and the likelihood of observing bare earth pixels that aren't obscured by clouds and shadows.
A significant advantage of the Sentinel-2 images is an improvement in spatial resolution with 4 bands at 10 metres compared to 30 metres for Landsat. This provides a 9 times improvement in spatial resolution with broad application in geological mapping, mineral exploration and natural resource management. In collaboration with the Terrestrial Ecosystems Research Network, the previous Barest Earth products have been used to map soil properties across the nation. These new finer resolution products will allow us to improve the spatial resolution of these soil property maps at the local farm and paddock scale.
Comparison of (a) Sentinel-2 3-2-1 true colour with seasonal green vegetation cover (b) Sentinel-2 Barest Earth 3-2-1 true colour and (c) Landsat TM 30 year Barest Earth 3-2-1- true colour. Image over part of the township of Temora central NSW (lower left). The Barest Earth products significantly removes the masking of seasonal cropping/vegetation that would otherwise blanket the underlying soil response. Increased spatial resolution of the Sentinel-2 Barest Earth (b) compared with the 30-year Landsat Barest Earth (c)
The Barest Earth images can be used to map regolith that consists mainly of weathered rock and sediments. Soil can be seen as the upper most part of the regolith profile. Australia's surface is mostly regolith, demonstrated by the characteristic red hue of the continent due to the abundance of iron oxides.
The Barest Earth Sentinel-2 bands are available as 1:250 000 map sheet area tiles, each with 10 bands. Each tile has a slight buffer overlap of 60 meters to ensure no pixel is missing between adjacent sheet area boundaries.
Read the Sentinel-2 Barest Earth extended abstract and download the Sentinel-2 Barest Earth tiles.
This project laid the foundations for a national view of Australia's surface and subsurface geology, underpinning our understanding of the continent's mineral, energy and groundwater potential.
Geoscience Australia's Exploring for the Future Data Discovery Portal provides public access to historical as well as new geoscience data and tools acquired and developed during the Exploring for the Future program. The Portal provides the ability for government planners and regulators, academia, industry and communities to access data and apply a range of assessment tools to support evidence-based decisions.