DEA Fractional Cover (Landsat)

Version:: Landsat 5/7: 2.5.0, Landsat 8/9: 2.5.1
Type:: Derivative, Raster
Resolution:: 30 m
Coverage:: 16 Aug 1986 to Present
Data updates:: Daily frequency, Ongoing

Overview

About

Digital Earth Australia (DEA) Fractional Cover splits landscape observation data into three parts — or fractions — enabling measurement of green (leaves, grass, and growing crops), brown (branches, dry grass or hay, and dead leaf litter), and bare ground (soil or rock) in any area of Australia at any time since 1986.

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Key specifications

For more specifications, see the Specifications tab.

Technical name	Geoscience Australia Landsat Fractional Cover Collection 3
Bands	4 bands of data (bs, pv, and more)
Catalogue ID	145498
Currency	See currency and the latest update date
Parent product	Landsat 5, 7, 8, and 9 NBART and Observational Attributes
Collection	Geoscience Australia Landsat Collection 3
Tags	geoscience_australia_landsat_collection_3, green_vegetation, non_green_vegetation, bare_soil
Licence	Creative Commons Attribution 4.0 International Licence

Cite this product

Data citation

Lymburner, L., 2021. Geoscience Australia Landsat Fractional Cover Collection 3. Geoscience Australia, Canberra. https://pid.geoscience.gov.au/dataset/ga/145498

Paper citation

Scarth, P., Roder, A., Schmidt, M., 2010. Tracking grazing pressure and climate interaction - the role of Landsat fractional cover in time series analysis. Proceedings of the 15th Australasian Remote Sensing & Photogrammetry Conference. http://dx.doi.org/10.6084/M9.FIGSHARE.94250

Publications

Scarth, P., Roder, A. and Schmidt, M. (2010). Tracking grazing pressure and climate interaction - the role of Landsat fractional cover in time series analysis. Proceedings of the 15th Australasian Remote Sensing & Photogrammetry Conference. http://dx.doi.org/10.6084/M9.FIGSHARE.94250

Schmidt, M., Denham, R. and Scarth, P. (2010), Fractional ground cover monitoring of pastures and agricultural areas in Queensland. Proceedings of the 15th Australasian Remote Sensing & Photogrammetry Conference. https://www.researchgate.net/publication/236143308_FRACTIONAL_GROUND_COVER_MONITORING_OF_PASTURES_AND_AGRICULTURAL_AREAS_IN_QUEENSLAND

Description

Background

Fractional cover data can be used to identify large scale patterns and trends and inform evidence based decision making and policy on topics including wind and water erosion risk, soil carbon dynamics, land management practices and rangeland condition.

This information is used by policy agencies, natural and agricultural land resource managers, and scientists to monitor land conditions over large areas over long time frames.

What this product offers

Fractional Cover (FC), developed by the Joint Remote Sensing Research Program, is a measurement that splits the landscape into three parts, or fractions:

Green (leaves, grass, and growing crops)
Brown (branches, dry grass or hay, and dead leaf litter)
Bare ground (soil or rock)

Digital Earth Australia (DEA) uses Fractional Cover to characterise every 30 m square of Australia for any point in time from 1986 to today.

Applications

Fractional cover provides valuable information for a range of environmental and agricultural applications, including:

soil erosion monitoring
land surface process modelling
land management practices (e.g. crop rotation, stubble management, rangeland management)
vegetation studies
fuel load estimation
ecosystem modelling
land cover mapping

Technical information

Fractional Cover (FC) provides information about the the proportions of green vegetation, non-green vegetation (including deciduous trees during autumn, dry grass, etc.), and bare soils for every 30m x 30m ground footprint across the whole Australian continent. This information is available for every cloud free satellite observation over Australia from 1986 till now. FC can potentially provide insights into the interplay and changes in areas of dry vegetation and/or bare soil as well as allowing the mapping of green vegetation extent.

The FC algorithm was developed by the Joint Remote Sensing Research Program (JRSRP) and is described in Scarth et al. (2010). It has been implemented by Geoscience Australia for every observation from Landsat Thematic Mapper (Landsat 5), Enhanced Thematic Mapper (Landsat 7) and Operational Land Imager (Landsat 8 and 9) acquired since 1986. It is calculated from terrain corrected surface reflectance (DEA Surface Reflectance).

Data layers

The product consists of four data layers:

The fractional cover of green vegetation (PV): Fraction of green cover including green groundcover and green leaf material over all strata, within the Landsat pixel, as percentages
The fractional cover of non-green vegetation (NPV): Fraction of non green cover including litter, dead leaf and branches over all strata, within the Landsat pixel, as percentages
The fractional cover of bare soil (BS): Fraction of bare ground including rock, bare and disturbed soil, within the Landsat pixel as percentages
The fractional cover unmixing error (UE): Eclidean Norm of the Residual Vector

The values for this product are scaled as follows:

For the fractional cover bands (PV, NPV, BS)
0-100 = fractional cover values that range between 0 and 100%

Due to model uncertainties and the limitations of the training data, some areas may show cover values in excess of 100%. These areas can either be excluded or treated as equivalent to 100%

Processing steps

Fractional cover is processed using the Landsat Surface Reflectance archive, and requires green, red, nir, swir1 and swir2 bands. Fractional Cover Code Repository

The fractions are retrieved by inverting multiple linear regression estimates and using synthetic endmembers in a constrained non-negative least squares unmixing model. For more information, see Scarth et al. (2010) and Schmidt et al. (2010), and a brief description of the FC algorithm on the TERN website.

The bare soil, green vegetation and non-green vegetation end members used for fractional cover can be found here, and was last updated on the 9th of June 2017: End members

For the unmixing error (UE) band, the values are scaled between 0 and 127. High unmixing error values represent areas of high model uncertainty (areas of water, cloud, cloud shadow or soil types/colours that were not included in the model training data).

Landsat 8 and 9 OLI have different relative spectral response curves to the Landsat 5 TM and Landsat 7 ETM+ sensors. To account for this a spectral band adjustment factor is applied to the Landsat 8 and 9 data to make it more similar to reflectance as measured by Landsat 7. Continuity of Reflectance Data between Landsat-7 ETM+ and Landsat-8 OLI, for Both Top-of-Atmosphere and Surface Reflectance: A Study in the Australian Landscape refer to Table 2 for coefficients used.

Lineage

While originally calibrated in Queensland, a large collaborative effort between The Department of Agriculture - ABARES and State and Territory governments to collect additional field data has enabled the calibration/validation to extend to the entire Australian continent.

1390 field data sites were used to train the model, and a separate 1565 sites were used to evaluate the model accuracy.

FC was made possible by the collaborative framework established by the Terrestrial Ecosystem Research Network (TERN) through the National Collaborative Research Infrastructure Strategy (NCRIS) and collaborative effort between state and Commonwealth governments.

References

Flood, N. (2014). Continuity of reflectance data between Landsat-7 ETM+ and Landsat-8 OLI, for both top-of-atmosphere and surface reflectance: A study in the Australian landscape. Remote Sensing, 6(9), 7952–7970. https://doi.org/10.3390/rs6097952

Muir, J., Schmidt, M., Tindall, D., Trevithick, R., Scarth, P. and Stewart, J.B. (2011). Guidelines for field measurement of fractional ground cover: a technical handbook supporting the Australian Collaborative Land Use and Management Program. Queensland Department of Environment and Resource Management for the Australian Bureau of Agricultural and Resource Economics and Sciences.

Quality

Accuracy

To provide an estimate of accuracy the FC algorithm results were compared with 1565 field sites that were not used to train the FC model.

Based on the comparison with this independent field data the FC product has an overall Root Mean Squared Error (RMSE) of 11.9%. The error margins vary for the three different layers:

green RMSE: 11.9%,
non-green RMSE: 17.1%
bare RMSE: 14.6%

The effect of soil moisture may impact the accuracy of the FC product, and the similarity between some bare soil endmembers and non-photosynthetic vegetation endmembers can lead to model instability. Soil types/colours that were not included in the model training data may introduce additional errors. Pixels that show poor model stability are flagged in the model error band as a value of 2, and can be omitted from further analysis if necessary.

FC products have no water masking applied, so erroneous values for green vegetation over the water may appear. These should be ignored and can be masked out by applying the Water Observations (WO) layer.

Occasionally the sum of the three components is not equal to 100%. Differences are usually small and are not rounded in order to preserve what may be useful seasonal indicators.

Landsat 8/9 OLI has different relative spectral response curves to the Landsat 5 TM and Landsat 7 ETM+ sensors. To account for this a spectral band adjustment factor is applied to the Landsat 8/9 data to make them more similar to reflectance as measured by Landsat 7. The adjustment factors are described in more detail in Flood (2014).

Whilst the same training data has been used to train both the JRSRP fractional cover product and the DEA fractional cover product, differences in the terrain corrected surface reflectance data that are used as model inputs mean that the two products are not identical. The differences between the two products are typically less than 5% for the bare soil and non-green cover types, and typically less than 10% for green cover.

Quality assurance

The following details are an extract from the information contained at: https://portal.tern.org.au/metadata/22026

The bare soil, green vegetation and non-green vegetation endmembers are calculated using models linked to an intensive field sampling program that covers a wide range of Australian landscapes covering a wide variety of vegetation, soil and climate types were sampled to measure overstorey and ground cover following the procedure outlined in Muir et al (2011).

Specifications

Bands

Bands are distinct layers of data within a product that can be loaded using the Open Data Cube (on the DEA Sandbox or NCI) or DEA’s STAC API. Here are the bands of the product: ga_ls_fc_3.

	Aliases	Resolution	No-data	Units	Type	Description
bs	bare	30 m	255	Percent	uint8	BS: The fractional cover of bare soil.
pv	green_veg	30 m	255	Percent	uint8	PV: The fractional cover of green vegetation.
npv	dead_veg	30 m	255	Percent	uint8	NPV: The fractional cover of non-green vegetation.
ue	err	30 m	255	-	uint8	UE: The fractional cover unmixing error.

For more information on these bands, see the Description tab.

Product information

This metadata provides general information about the product.

Product ID	ga_ls_fc_3	Used to load data from the Open Data Cube.
Short name	DEA Fractional Cover (Landsat)	The name that is commonly used to refer to the product.
Technical name	Geoscience Australia Landsat Fractional Cover Collection 3	The full technical name that refers to the product and its specific provider, sensors, and collection.
Version	Landsat 5/7: 2.5.0, Landsat 8/9: 2.5.1	The version number of the product. See the History tab.
Lineage type	Derivative	Derivative products are derived from other products.
Spatial type	Raster	Raster data consists of a grid of pixels.
Spatial resolution	30 m	The size of the pixels in the raster.
Temporal coverage	16 Aug 1986 to Present	The time span for which data is available.
Update frequency	Daily	The expected frequency of data updates. Also called ‘Temporal resolution’.
Update activity	Ongoing	The activity status of data updates.
Currency	See the Currency Report	Currency is a measure based on data publishing and update frequency.
Latest update date	Currency Report	See Table A of the report.
Catalogue ID	145498	The Data and Publications catalogue (eCat) ID.
Licence	Creative Commons Attribution 4.0 International Licence	See the Credits tab.

Product categorisation

This metadata describes how the product relates to other DEA products.

Parent product	Landsat 5, 7, 8, and 9 NBART and Observational Attributes
Collection	Geoscience Australia Landsat Collection 3
Tags	geoscience_australia_landsat_collection_3, green_vegetation, non_green_vegetation, bare_soil

Access

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DEA Maps	See it on a map	Learn how to use DEA Maps.
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Data sources	Access the data on AWS Access the data on NCI	Learn how to access the data via AWS.
Code examples	View code examples	Learn how to use the DEA Sandbox.
Web services	Get via web service	Learn how to use DEA’s web services.

History

Version history

Versions are numbered using the Semantic Versioning scheme (Major.Minor.Patch). Note that this list may include name changes and predecessor products.

Landsat 5/7: 2.5.0, Landsat 8/9: 2.5.1	-	Current version
v2.3.1	of	DEA Fractional Cover (Landsat)
v2.2.1	of	DEA Fractional Cover (Landsat)

Changelog

Version: 2.5.0 and 2.5.1

Landsat 9 was incorporated into this product starting in October 2021. Version 2.5.0 includes data from Landsat 5 and Landsat 7, while version 2.5.1 contains data for both Landsat 8 and Landsat 9. The same set of coefficients is applied to the input ARD bands of Landsat 8 and 9 to make their input range comparable to that of Landsat 5 and 7 ARD data.

Credits

Acknowledgments

Landsat data is provided by the United States Geological Survey (USGS) through direct reception of the data at Geoscience Australias satellite reception facility or download.

The fractional cover algorithm was developed by the Joint Remote Sensing Research Program (JRSRP) and is described in Scarth et al. (2010).

While originally calibrated in Queensland, a large collaborative effort between the Department of Agriculture, the Australian Bureau of Agricultural and Resource Economics (ABARES) and State and Territory governments to collect additional calibration data has enabled the calibration to extend to the entire Australian continent. Fractional Cover was made possible by new scientific and technical capabilities, the collaborative framework established by the Terrestrial Ecosystem Research Network (TERN) through the National Collaborative Research Infrastructure Strategy (NCRIS), and collaborative effort between state and Commonwealth governments.

License and copyright

Released under Creative Commons Attribution 4.0 International Licence.