A (GlobCover) Picture is Worth a Thousand Words
There's satellite imagery and then there's satellite imagery: as part of the European Space Agency's (ESA) GlobCover project, the most detailed pictures ever of the Earth's land surface (ten times sharper than similar previous efforts) have been created with the Envisat environmental satellite.
These images, which are bimonthly global composites for the periods between May and June 2005 and March to April 2006, can be accessed through the ESA's GlobCover website's newly created map server tool. In all, around 40 terabytes of imagery were retrieved between December 2004 and June 2006 and processed to produce these composites, which will aid the international community in modeling the impacts of climate change and worldwide land-use trends and in studying ecosystems.
Ron Witt of the United Nations Environment Program (UNEP) explained that the data sets obtained through the GlobCover project should "allow UNEP to do frequent monitoring of environmentally-critical sites and known 'hot spots' in areas we have under examination around the globe, and to update our knowledge of such changing environmental conditions.""Combined with the Corine data on which the current accounts of land cover change at the European scale are based, a regularly updated GlobCover is expected to play a key role in the implementation of nowcasting procedures, necessary for delivering up-to-date data on land cover change at the European scale at a pace compatible with the main socio-economic indicators," said Jean-Louis Weber in framing the importance of the GlobCover project in the context of the European Environmental Agency's (EEA) mission.
Another U.N. group, the Food and Agriculture Organization (FAO), plans on making extensive use of the GlobCover images to support its activities, which will include monitoring "dynamic environmental parameters such as rainfall and vegetation condition for FAO's global and national food security early warning programs."
According to the FAO's John Latham, "it will also significantly contribute to the monitoring and assessment of global land cover and as such will support the contribution of FAO to the assessment of land degradation and the monitoring of global forest cover."
The Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument, operating in Full Resolution Mode, was used to acquire the images in polar orbit at an altitude of 800 km with a spatial resolution of 300 m. The composites are created by processing the MERIS images together in a standardized fashion: thirteen out of fifteen MERIS spectral bands are processed with an advanced algorithm that includes tools for cloud screening, ortho-rectification and full atmospheric correction, which accounts for the effect of aerosol. An automatic and regionally adjusted classification of the global composites is then used to obtain the global land cover maps.