|Remote Sensing Imagery: Making Sense of Available Data|
By Alex de Sherbinin (CIESIN, Columbia University)
Environment, January/February 2002, Volume 44, Number 1, pages 3-4. © Heldref Publications, 2002. www.heldref.org. Posted with permission.
Remote sensing is vital for understanding a wide range of environmental processes, but to non-specialists the technology may appear forbidding and cloaked in mystery. The names of satellite instruments alone AVHRR, ETM+, JERS, MODIS, SeaWiFS seem calculated to produce incomprehension. While it is true that a complete understanding of remote sensing image interpretation requires years of training, it is equally true that lay people can learn the basic principles of remote sensing fairly quickly. The purpose of this article is to provide a guide to on-line resources for those wishing to learn more about the technology, and secondarily, to point readers to some websites that demonstrate its power and capabilities in the area of international environmental policy.
Remote sensing tutorials are available at a number of locations. The most comprehensive tutorials are available at NASAs Goddard Space Flight Center (http://rst.gsfc.nasa.gov/) and the Canadian Centre for Remote Sensing (http://www.ccrs.nrcan.gc.ca/ccrs/eduref/tutorial/tutore.html). Master lists of on-line remote sensing resources are provided by the International Society for Photogrammetry and Remote Sensing (http://www.isprs.org/links/tutorial.html) and the Technical Research Center of Finland's virtual library (http://www.vtt.fi/tte/research/tte1/tte14/virtual/), both of which are updated regularly. From these points of departure you can find the most relevant educational resources on the web.
Readers more interested in pretty pictures than in the technicalities of remote sensing may prefer to go directly to on-line image galleries. NASAs Visible Earth (http://visibleearth.nasa.gov/) provides an excellent array of imagery grouped conveniently into categories such as agriculture, biosphere, human dimensions, and oceans. For those wishing up-close shots of familiar locations or current events (such as ground zero of the World Trade Center disaster), Space Imaging displays images from its high resolution IKONOS sensor at http://www.spaceimaging.com/. The Tropical Rainforest Information Center (http://www.bsrsi.msu.edu/trfic/) hosts a series of deforestation "movies" morphed images of land cover change over time under its Rainforest Report Card.
Because of the large number of active sensors, and the fact that so many are being launched each year, it is difficult to maintain comprehensive lists of satellites and sensors. Nevertheless, a few sites provide lists of sensors and specifications that are useful, especially for those with sufficient background to be able to decipher the technical jargon (see ISCIENCEs glossary and sensor list at http://www.isciences.com/NewSite/sensors/current.html).
A number of free-ware image processing packages are available for download from the web. One such package, Multispec® (http://www.ece.purdue.edu/~biehl/MultiSpec/), runs on Mac and PC platforms, and allows for display, classification, and statistical analysis of multispectral imagery (e.g., Landsat or SPOT imagery). UNESCOs Bilko project (http://www.unesco.bilko.org) provides an educational image processing package tailored to coastal and marine applications. Free-ware packages and declining costs of imagery mean that even small non-profit organizations can afford to do their own image processing. Landsat scenes can be purchased online for as little as US$50 at http://landsat.org, and Advanced Very High Resolution Radiometer (AVHRR) scenes covering larger regions can be purchased for $190 from the U.S. Geological Survey (http://earthexplorer.usgs.gov).
Environmental applications of remote sensing have been a mainstay in the field, largely because most remote sensing scientists receive their substantive training in Earth sciences and geography. The interest in remote sensing as a tool for the development, monitoring and enforcement of environmental treaties stems from parallel developments in the areas of Earth observation and international environmental diplomacy. On the one hand, instruments are being launched with ever more impressive capabilities, and vendors are looking for new markets. On the other, the numbers of treaties in force are constantly increasing, and decision makers (i.e., Contracting Parties) are looking for easier ways to monitor their own and third party compliance.
A number of sites provide information on the application of remote sensing to environmental agreements. A good starting point is the Socioeconomic Data and Application Center (SEDAC) web site on remote sensing and environmental treaties (http://sedac.ciesin.columbia.edu/rs-treaties). It provides a report of the workshop by the same title, several papers, and links to related initiatives, such as the Integrated Global Observing Strategy (http://www.igospartners.org), which is a major partnership of data providers and data users focused on atmospheric, oceanographic and land-based observations.
Many environmental treaties lack strong enforcement mechanisms. The ones that do provide for enforcement, however, have received greater attention from remote sensing scientists. An example of an application tied to treaty enforcement is the use of remote sensing for marine oil spill detection, which is currently taking place under the auspices of the Bonn Agreement among the nations bordering the North Sea (http://www.bonnagreement.org/). The advantages of such monitoring is that it can cover much larger areas at lower cost than traditional aerial reconnaissance.
The Kyoto Protocol, when implemented, will require substantial data on greenhouse gas (GHG) emissions and carbon sources and sinks. Satellite sensors currently can measure carbon monoxide, methane, nitrous oxide and aerosols, but the technology is not at the point where it can easily inventory GHG emissions for a given country (this data is usually obtained from fossil fuel consumption and other proxy measures). However, remote sensing can provide valuable information on agricultural and forest land, which are important sources and sinks of carbon and other GHGs. The Global Monitoring for Environment and Security initiative (http://gmes.jrc.it/) of the European Commission is producing a number of experimental products that demonstrate remote sensing capabilities in support of Kyoto. For a report on a joint ISPRS and University of Michigan workshop that examined the technical specifications of systems needed under Kyoto, see http://www.eecs.umich.edu/kyoto/.
Remote sensing applications in support of the biodiversity conventions the Convention on Biological Diversity, the Convention on International Trade in Endangered Species, and the Ramsar Convention on Wetlands are not generally tied to binding provisions, but are useful nonetheless for providing guidance to Contracting Parties on drivers of biodiversity loss and successful conservation approaches. See http://www.earth.nasa.gov/outreach/conservationbiology/ for conclusions of a workshop on remote sensing applications for biodiversity conservation. One concrete example of remote sensing in support of a regional biodiversity treaty is the Mesoamerican Biological Corridor initiative (see page XX). Its web site provides detailed information on the imagery and methodologies utilized to plan a series of interconnected protected areas to facilitate wildlife migration (http://www.ghcc.msfc.nasa.gov/corredor/).
Fisheries and marine treaties, and the Convention to Combat Desertification, have also witnessed the development of experimental applications. Remote sensing imagery may be particularly useful for national reports to the CCD, given that inter-annual changes in the extent of desert areas (as measured by the normalized-difference vegetation index or NDVI) can be easily measured using AVHRR data. More information on a variety of treaty-specific applications can be found in the paper "Remote Sensing in Support of Multilateral Environmental Agreements" by de Sherbinin and Giri (2001) at the SEDAC website listed above.