This dataset was supplied to the Bioregional Assessment Programme by a third party and is presented here as originally supplied. The metadata was not provided by the data supplier and has been compiled by the programme based on known details.
This dataset was created for the Galilee subregion by performing the Tasselled Cap Index on Landsat data using Digital Earth Australia (DEA) to create a wetness summary image. This wetness summary image identifies open water or wet vegetation presence in pixel by proportion of images in which pixel exceeded tasselled cap wetness threshold over 30 year archive.
DEA is an analysis platform for satellite imagery and other Earth observations. Today, it translates 30 years of Earth observation data (taken every two weeks at 25 metre squared resolution) and tracks changes across Australia in unprecedented detail, identifying soil and coastal erosion, crop growth, water quality, and changes to cities and regions.
The tasselled cap wetness in the landscape summary output is produced using DEA. Landsat surface reflectance data at 25 m resolution with information in the red, green, blue, near infra-red and short-wave infra-red spectral bands are retrieved from the DEA archive using a spatial query for Galilee subregion. Clouds and areas of terrain shadow are masked from the surface reflectance data. A tasselled cap transformation is performed on each of the surface reflectance bands to produce a per-pixel 'wetness' value. This method is based on the tasselled cap transformation of Crist EP (1985) A TM tasselled cap equivalent transformation for reflectance factor data. Remote Sensing of Environment 17(3), 301-306, but only uses the component of transformed surface reflectance in the 'wetness' direction to identify the presence of water and wet vegetation.
Areas of water and wet vegetation are highlighted where pixels exceed a specified wetness threshold. Pixels exceeding the wetness threshold are counted through the temporal image archive. This count is then normalised by the number of times that the pixel was observed (cloud free). The wetness in the landscape summary is then presented as the percentage of scenes where the pixel has contained water or wet vegetation through time. Selecting a spatial transect of interest (e.g. a line that follows a river, or crosses a wetland or spring) allows for retrieval of the wetness threshold data for each image pixel along the transect line.
Geoscience Australia (2017) Galilee normed TCI landsat and traverses. Bioregional Assessment Source Dataset. Viewed 10 December 2018, http://data.bioregionalassessments.gov.au/dataset/c3f82187-e16b-4765-b6db-4d248976541d.