Australian Reflectance Grid 25 (ARG25)
A beta release of the Australian Reflectance Grid 25 (ARG25V 0.1) is now available. This product was produced through the Unlocking the Landsat Archive project. The data are implemented using Open Geospatial Consortium (OGC) and International Standards Organisation (ISO) compliant services.
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.
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.
What is available?
Preliminary results include approximately 184,000 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 which 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 1986 to 2013. 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 560KB] [ DOC 192KB]. 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 affects, sun and sensor angles have been corrected for in each terrain corrected scene. The benefit of this, is that each 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.
The published services offered in ARG25 Beta adhere to the following conventions:
- Each scene is published as a single WMS and WCS service;
- Each service consists of six layers (one layer for each band);
- WMS service has an additional 7th layer which is a false colour composite (ie. combination of Bands 7, 4 and 1); and
- Each service URL includes a scene ID with an identifier provided from the metadata as seen below:
In this example the path row component of the scene is read as path 115 and row 79 acquired on the 21st of October 2008.
How to access?
The simplest way to preview and/or download ARG25 data is via our newly launched Data Discovery and Delivery Service. Type in "Landsat" in the "product search" box above the map and click on search button to view a list of available data. You can refine your search criteria by entering location bounding box and date using "Advanced" search option.
Clicking on an item in the list will open a new page with a metadata record - download link is on the right side of the page. Alternatively, all datasets marked with ‘honeycomb’ icon indicate the data is available for preview as OGC web services. Click on the icon and follow the links in the pop-up window to access the information and/or add to the map.
Users familiar with web services and processes can extract data directly into a tool kit and/or processing platform. The following Geoscience Australia URLs can be used to access these services:
- Catalogue Service (CSW)
- The catalogue service enables search and discovery of the ARG25 data available via the WMS and WCS services. Following is the catalogue service URL in base form and in the form of a GetCapabilities request:
- Base URL - http://eos.ga.gov.au/geonetwork/srv/en/csw?service=CSW
- GetCapabilities request - http://eos.ga.gov.au/geonetwork/srv/eng/csw?service=CSW&request=GetCapabilities
- Data services (WMS, WCS)
- Each Landsat-5 and Landsat-7 scene has its own WMS and WCS service endpoint. The URLs for the WMS and WCS service end points are contained within the metadata describing each scene, available by searching the catalogue service.
- Web Map Service (WMS)
- The WMS services deliver rendered images of the full resolution data, for the purposes of providing a quick look and previewing the data. As described above, the URLs to the WMS services are obtained from the metadata available from the catalogue service. Following is an example URL in base form and in the form of a GetCapabilities request:
- Base URL - http://eos.ga.gov.au/thredds/wms/LANDSAT/2008/10/LS7_ETM_NBAR_P54_GANBAR01-002_115_079_20081021_BX.nc
- GetCapabilities request - http://eos.ga.gov.au/thredds/wms/LANDSAT/2008/10/LS7_ETM_NBAR_P54_GANBAR01-002_115_079_20081021_BX.nc?service=WMS&version=1.3.0&request=GetCapabilities
- Web Coverage Service (WCS)
- The WCS services provide access to the full resolution data. As described above, the URLs to the WCS services are obtained from the metadata available from the catalogue service. Following is an example URL in base form and in the form of a GetCapabilities request:
- Base URL - http://eos.ga.gov.au/thredds/wcs/LANDSAT/2008/10/LS7_ETM_NBAR_P54_GANBAR01-002_115_079_20081021_BX.nc
- GetCapabilities request - http://eos.ga.gov.au/thredds/wcs/LANDSAT/2008/10/LS7_ETM_NBAR_P54_GANBAR01-002_115_079_20081021_BX.nc?service=WCS&version=1.0.0&request=GetCapabilities
Viewing downloaded netCDF dataPanoply is a free Java application that enables making plots of two-dimensional geo-gridded data from netCDF . It can be downloaded from NASA website at: http://www.giss.nasa.gov/tools/panoply/
Please note: The web services provided above are delivered from a new cloud infrastructure at the National Computing Infrastructure which is in a pre-production phase.
If you are having trouble in accessing the URL’s above, please try later, in failing again contact firstname.lastname@example.org to get up-to-date advice on whether the infrastructure is offline for a period of time.
Any comments or feedback on the ARG25 Product Information Beta Release document [ PDF 560KB] [ DOC 192KB] are welcome, please send these to email@example.com