Data

Geoscience Australia Sentinel-2 Tidal Composites Calendar Year Collection 3

Name: Geoscience Australia Sentinel-2 Tidal Composites Calendar Year Collection 3
Published: 2025

Geoscience Australia

Newey, V. ; Bishop-Taylor, R. ; Phillips, C. ; Sagar, S.

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ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rfr_id=info%3Asid%2FANDS&rft_id=info:doi10.26186/150381&rft.title=Geoscience Australia Sentinel-2 Tidal Composites Calendar Year Collection 3&rft.identifier=10.26186/150381&rft.publisher=Commonwealth of Australia (Geoscience Australia)&rft.description=Intertidal zones are coastal environments exposed to both air and water, at low and high tide consecutively, and include sandy beaches, tidal flats, rocky shores and reefs. They also characterise critical coastal habitats and ecosystems, supporting a wide range of species and ecosystem-services. Increasingly though, these dynamic environments are faced with threats from land reclaimation, coastal erosion and rising sea levels, amongst others. The ever-changing nature of the tides makes it hard to systematically capture consistent imagery of the intertidal zone, particularly across large regions and especially in remote areas of the country. Geomedian statistical techniques provide a robust method to combine tide-attributed time-series satellite imagery and produce representative and artefact free imagery ‘composites’ of Australia’s coastal high and low tide environments.This product provides a suite of cloud-free composite Sentinel-2 satellite datasets that enable imaging of Australian coastal intertidal zones at both high and low tide. Using a geometric median (geomedian), the highest and lowest 15 % of observed tidal images in Digital Earth Australia (DEA)’s Sentinel-2 archive are combined to deliver annual snapshots of Australian coastal high and low tide environments. Spatially and temporally aligned to the DEA Intertidal product suite (https://knowledge.dea.ga.gov.au/data/product/dea-intertidal), this product (also known as DEA Tidal Composites) is an annually updated data suite, generated from rolling 3-year epochs, with a minimum of 10 m spatial resolution.Tidal composites are produced by tidally attributing Sentinel-2 satellite images though pairing with pixel-based local tidal modelling, generated from a selected ensemble of the best performing global tide models under local conditions. The ensemble tidal modelling approach was implemented to account for the varying performance and biases of existing global ocean tide models across the complex tidal regimes and coastal regions of Australia. Tidal attribution allows the imagery archive to be sorted by tide height rather than date, so the intertidal zone can be visualised during any stage of the tide regime.DEA Tidal Composites include 25 layers of data, separated into lowtide, hightide and quality assurance categories. Lowtide and hightide layers represent composites of the synthetic geomedian surface reflectance from Sentinel-2A, -2B and -2C analysis-ready data streams. The geomedian calculation maintains the spectral relationships between bands, ensuring that the DEA Tidal Composites product delivers robust and valid surface reflectance spectra suitable for uses such as habitat mapping and delivers cloud free and noise reduced visualisation of the shallow water and intertidal coastal regions of Australia. Quality assurance layers are provided to support interpretation of the lowtide and hightide datasets and include the tide-height thresholds above and below which associated images were included in the compositing process and the count of clear input images that contributed to each pixel in the composites.Statement: The DEA Tidal Composites product suite extends the concepts developed in the DEA High and Low Tide Composites product but instead uses 10 m Sentinel-2 data and tide modelling is completed at the pixel scale. Additionally, a rolling 3-year epoch is used to calculate the product on an annual time scale.This shift to a more dynamic product suite is achieved through a pixel-based tide-modelling algorithm, improved data resolution and density through the use of Sentinel-2 data and pre-processing improvements that include cloud, cloud-shadow and glint-angle filtering to remove contaminated pixels.&rft.creator=Newey, V. &rft.creator=Bishop-Taylor, R. &rft.creator=Phillips, C. &rft.creator=Sagar, S. &rft.date=2025&rft.coverage=westlimit=112.00; southlimit=-44.00; eastlimit=154.00; northlimit=-9.00; projection=GDA94 / Australian Albers (EPSG:3577)&rft.coverage=westlimit=112.00; southlimit=-44.00; eastlimit=154.00; northlimit=-9.00; projection=GDA94 / Australian Albers (EPSG:3577)&rft_rights=Creative Commons Attribution 4.0 International Licence https://creativecommons.org/licenses/by/4.0/&rft_rights=© Commonwealth of Australia (Geoscience Australia) 2025&rft_rights=Australian Government Security Classification System https://www.protectivesecurity.gov.au/publications-library/policy-8-classification-system&rft_subject=geoscientificInformation&rft_subject=coast&rft_subject=composite&rft_subject=satellite imagery&rft_subject=DEA – Digital Earth Australia&rft_subject=geometric median&rft_subject=Earth system sciences&rft.type=dataset&rft.language=English Access the data

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https://creativecommons.org/licenses/by/4.0/

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https://www.protectivesecurity.gov.au/publications-library/policy-8-classification-system

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Full description

Intertidal zones are coastal environments exposed to both air and water, at low and high tide consecutively, and include sandy beaches, tidal flats, rocky shores and reefs. They also characterise critical coastal habitats and ecosystems, supporting a wide range of species and ecosystem-services. Increasingly though, these dynamic environments are faced with threats from land reclaimation, coastal erosion and rising sea levels, amongst others. The ever-changing nature of the tides makes it hard to systematically capture consistent imagery of the intertidal zone, particularly across large regions and especially in remote areas of the country. Geomedian statistical techniques provide a robust method to combine tide-attributed time-series satellite imagery and produce representative and artefact free imagery ‘composites’ of Australia’s coastal high and low tide environments.

This product provides a suite of cloud-free composite Sentinel-2 satellite datasets that enable imaging of Australian coastal intertidal zones at both high and low tide. Using a geometric median (geomedian), the highest and lowest 15 % of observed tidal images in Digital Earth Australia (DEA)’s Sentinel-2 archive are combined to deliver annual snapshots of Australian coastal high and low tide environments. Spatially and temporally aligned to the DEA Intertidal product suite (https://knowledge.dea.ga.gov.au/data/product/dea-intertidal), this product (also known as DEA Tidal Composites) is an annually updated data suite, generated from rolling 3-year epochs, with a minimum of 10 m spatial resolution.

Tidal composites are produced by tidally attributing Sentinel-2 satellite images though pairing with pixel-based local tidal modelling, generated from a selected ensemble of the best performing global tide models under local conditions. The ensemble tidal modelling approach was implemented to account for the varying performance and biases of existing global ocean tide models across the complex tidal regimes and coastal regions of Australia. Tidal attribution allows the imagery archive to be sorted by tide height rather than date, so the intertidal zone can be visualised during any stage of the tide regime.

DEA Tidal Composites include 25 layers of data, separated into lowtide, hightide and quality assurance categories. Lowtide and hightide layers represent composites of the synthetic geomedian surface reflectance from Sentinel-2A, -2B and -2C analysis-ready data streams. The geomedian calculation maintains the spectral relationships between bands, ensuring that the DEA Tidal Composites product delivers robust and valid surface reflectance spectra suitable for uses such as habitat mapping and delivers cloud free and noise reduced visualisation of the shallow water and intertidal coastal regions of Australia. Quality assurance layers are provided to support interpretation of the lowtide and hightide datasets and include the tide-height thresholds above and below which associated images were included in the compositing process and the count of clear input images that contributed to each pixel in the composites.

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Statement:

The DEA Tidal Composites product suite extends the concepts developed in the DEA High and Low Tide Composites product but instead uses 10 m Sentinel-2 data and tide modelling is completed at the pixel scale. Additionally, a rolling 3-year epoch is used to calculate the product on an annual time scale.

This shift to a more dynamic product suite is achieved through a pixel-based tide-modelling algorithm, improved data resolution and density through the use of Sentinel-2 data and pre-processing improvements that include cloud, cloud-shadow and glint-angle filtering to remove contaminated pixels.

Notes

Purpose
Digital Earth Australia Tidal Composites are cloud-free imagery mosaics of Australia’s coasts, estuaries and reefs at low and high tide respectively. Calculated using a geometric median of Sentinel-2 imagery from the highest and lowest 15 % of observed tides, DEA Tidal Composites deliver an annually updated snapshot of high and low tide Australian coastal environments. Applications of this product include mapping cover types within the intertidal zone, visualising the full observed extent of the tidal range around the Australian continental coastline and monitoring for change in Australian coastal environments.

Created: 15 05 2025

Issued: 15 05 2025

Data time period: 2016-01-01 to

This dataset is part of a larger collection

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text: westlimit=112.00; southlimit=-44.00; eastlimit=154.00; northlimit=-9.00; projection=GDA94 / Australian Albers (EPSG:3577)

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Other Information

DEA Knowledge Hub page

url : https://knowledge.dea.ga.gov.au/data/product/dea-tidal-composites/ External Link

Link to DEA Data

url : https://data.dea.ga.gov.au/?prefix=derivative/ga_s2_tidal_composites_cyear_3 External Link

High tide and low tide composites 25m v. 2.0.0

local : 113843

Digital Earth Australia Intertidal

local : 149403

Identifiers

DOI : 10.26186/150381
URL : pid.geoscience.gov.au/dataset/ga/150381
global : 31064aab-3682-4564-9e47-8f1780affbc9