As most of you may well have recognised, the capabilities of satellite and airborne imagery reach far beyond providing an interesting background to a map or to spy into neighbour’s gardens.
Remote Sensing (RS) optical and radar data is widely used to create spatially coherent data sets of earth surface and atmospheric properties at local to global scales covering large areas. On the contrary, field measurements are usually spatially restricted. Some examples of RS data sets are climatic variables (e.g. surface temperature, humidity and precipitation), land surface properties (e.g. vegetation cover, type and condition, geology, soil moisture, inundation, salinity, terrain and human interactions). This is an area that Gaia Resources has been working with for some time now, and we thought it might be useful to provide a bit of an overview as to the capabilities as we see them.
RS data present an important resource for various applications e.g. the mapping of anthropogenic and natural changes, species distribution and habitat modeling, climate change and human impact assessment, mineral exploration and disaster management. There are many applications in agriculture and forestry that rely on RS data.
The fact that RS data is captured repeatedly (at least in the case of satellite data) covering vast as well as remote areas that are difficult to access makes its usage particularly attractive for many areas in Australia which is physically large but very sparsely populated and do therefore suffer from a lack of (temporally regular) ground measurements.
A wide range of freely available satellite data is distributed by NASA’s Earth Observing System Data and Information System (EOSDIS) data centers. These distribution centers provide different online search and order tools such as the USGS Global Visualisation Viewer GloVis, the USGS Earth Explorer (EE), the Warehouse Inventory Search Tool (WIST), or others that can be found on this website. A limited number of satellite data sets for Australia is being made available through Geoscience Australia.
The different portals offer various types of data sets from different sensors. These data do not only have different properties regarding their spatial, temporal and spectral resolution which determine the field of application of the data but there are furthermore different processing levels of each data sets. These processing levels range from raw radiometrically, geometrically and atmospherically uncorrected data to higher level products that have been corrected and contain derived information such as vegetation indicies. These two websites from the Goddard Earth Sciences and Information Services Center and the Land Processes Distributed Data Active Archive Center give an overview on some of the data sets available.
Products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat sensors are popular freely available data sets. MODIS is a key instrument aboard the Terra (EOS AM) and Aqua (EOS PM) satellites launched in 2000 which is viewing the earth surface every 1 to 2 days acquiring data in 36 spectral bands, or groups of wavelengths at a spatial resolution of 250 metres to one kilometer. These data are particularly useful to frequently monitor large areas over longer time periods. Some examples of information derived from MODIS data of different Australian regions are NDVI images visualizing a multi-year draught in eastern Australia, images of the 2011 fires in the Northern Territory or the 2010/2011 flooding in Victoria.
Landsat records data at a higher spatial resolution of up to 15 metres making it suitable for local scales but has a much lower revisit rate of about 16 days. The current sensor, Landsat-7 of the Landsat family launched in 1999 provides 7 spectral bands which makes Landsat-7 imagery ideal for vegetation, water and land monitoring. However, one Landsat scene covers a much smaller area of approximately 170 km north-south by 183 km east-west which implies that more scenes and therefore greater data processing efforts are needed for larger areas.
More and more data products providing higher spatial resolution are becoming commercially available. Examples are the WorldView Satellites and GeoEye which currently provide the highest spatial resolution available. Other sensors are for example Quickbird, Ikonos, SPOT, ALOS and ASTER.
Gaia Resources can provide a range of services to assist you with your remote sensing needs. You can follow up with me on this article by leaving a comment below or sending me an email.