A beta release of the Australian Reflectance Grid 25 (ARG25V 0.1) is now available. This product was produced by Geoscience Australia through the Unlocking the Landsat Archive project. The data are implemented using Open Geospatial Consortium (OGC) and International Standards Organisation (ISO) complaint services.
The ARG product suite provides standardised optical surface reflectance datasets for Australia using robust physical models to correct for variations in image radiance values due to atmospheric properties, and sun and sensor geometry. These products also feature integrated pixel quality flags to indicate whether the reflectance values in each grid cell are deemed to be affected by band saturation, cloud or cloud shadow, or contain null values.
It is the intention of GA that this suite of products will be available within a more general framework of nested grids. The grid cell sizes of products comprising this suite will be scalable to facilitate easy data comparison between different products. This format will greatly simplify comparison of image datasets acquired by different sensors at varying spatial scales.
The resulting stack of surface reflectance grids are effectively consistent over space and time, and will be instrumental in identifying and quantifying environmental change.
Preliminary results include approximately 110,000 individual Landsat 5 and Landsat 7 scenes processed to the ARG25 specification. The corrections provided in this product employ a robust physics-based model to correct for variations in image radiance values that result from variations in atmospheric properties and sun and sensor geometry present at the time the scene was acquired.
This dataset consists of 16-day repeat capture of Landsat-5 and Landsat-7 data over the Australian continent from 2000 to 2010. Each image covers a 185km x 185km geographic footprint and comprises seven discrete image bands. Data are available in NetCDF and/or GeoTIFF format.
Full product description and specifications are available from the ARG25 Product Information Beta Release document [PDF]. Subsequent releases will include the Pixel Quality Assessment layer (not included in this beta release).
This dataset can be used for time-series analysis with little to no further processing, because atmospheric effects, sun and sensor angles have been corrected for in each terrain-corrected scene. The benefit of this is that any scene covering the same geographic location can be directly compared with the same image acquired 8, 16, 32 days or 10 months apart, to detect direct changes in target or landscape features being viewed.
This beta version of the product has now been released and is available for download using the web services under a Creative Commons — Attribution 3.0 Australia (CC BY 3.0) licence.
The services are comprised of the following:
- a Catalogue Service for the web (CSW) allowing users to easily search ISO 19115 compliant metadata, which ARG25 data adheres to;
- Web Map Services (WMS) allowing users to obtain images of the data as quick looks to determine if the full resolution image will meet requirements; and
- Web Coverage Services (WCS) allowing users to obtain the full resolution data.
More information, and downloads are available on the Geoscience Australia website.
