Remote Sensing in Disaster Response

Remote sensing is the observation of phenomena at a distance, using a range of sensors for object identification based on their spectral signature, that is, the degree to which they absorb, reflect, backscatter, or emit light at various segments of the electromagnetic spectrum. Remote sensing can be accomplished from aircraft, from Earth-observing satellites, and from specialized in situ devices. Remote sensing technology has been used to facilitate first-responders’ decision support for a wide array of biogenic (naturally caused) and anthropogenic (man-made) disasters. Such natural disasters include landslides, snow disasters, volcanic eruptions, floods, hurricanes, earthquakes, tsunamis, droughts, famines, epidemics, and epizootics. Anthropogenic disaster responses that have benefited from remote sensing data include both inadvertent disasters (e.g., pollution, mining accidents, hazardous chemical and oil spills, train derailments) and deliberately caused disasters (e.g., acts of terror, arson-related fires). Aircraft have the advantage of capturing high-resolution panchromatic, multispectral and hyperspectral data from low-altitude flights, thereby providing high spatial and high spectral resolution, with a minimum of atmospheric distortion; but due to the infrequency of airborne sensor flights, they lack the high temporal resolution offered by satellite remote sensing. Geostationary satellites, whose orbits are in sync with Earth's rotation, capture data 24 hours per day, 7 days a week, while polar-orbiting satellites, depending on their revisit time, may collect data over the same area several times per day. Current analytical software for image analysis can minimize the impact of atmospheric distortion for both multispectral and hyperspectral orbiting sensors. Moreover, satellites with radar sensors can penetrate cloud cover.

In situ devices, ranging in sophistication from simple rain gauges to seismometers to NEXRAD Doppler Radar installations, monitor variables such as local precipitation, temperature, humidity, barometric pressure, water levels and quality, soil moisture, seismic activity, biological and chemical pollutants, and so on. Such in situ data can be used to supplement both aircraft-borne and space-borne sensor data. For disaster management purposes, other sources of data are also crucial, including demographic data, socioeconomic data, structural data, transportation network data, epidemiological data, and so on. Advanced technologies for in situ remote sensing are exemplified by micro unmanned aerial vehicles (MUAV), which can be deployed with sensors to detect explosives, toxic liquids or gases, radiation, biological or chemical weaponry, as well as hazardous industrial effluent.

The mechanism for integration of such diverse sources of information is typically a spatial database or geographic information system (GIS), which allows for multiple data layers and the means to analyze them in specific combinations. Online shared GIS allows end users to serve as sentinels during major disasters and participate in damage assessment. The other space-based technology that plays a vital role in disaster response is the constellation of geopositioning satellites, which can give exact location (i.e., latitude/longitude or Universal Transverse Mercator (UTM) information. There are now four such geopositioning constellations, the United States’ Global Positioning System (GPS), the European Union's Galileo, Russia's GLONASS, and China's Beidou (Compass).

The International Charter—Space & Major Disasters (http://www.disasterscharter.org) is a consortium of satellite-owning governments and companies that freely distributes satellite data through authorized users to areas that have experienced a [Page 2425]declared disaster. Such data are used for evacuation support, search and rescue, determining the extent of damage, facilitating access to medical and humanitarian shelter facilities, and so on. Since its first activation in February 2002, as of July 10, 2009, the charter has been activated 198 times, providing free satellite data to countries worldwide for virtually every known catastrophic event. Charter members and their space-based resources include the U.S. Geological Survey's Landsat, the National Oceanic and Atmospheric Administration's (NOAA) POES and GOES, Canada's RADARSAT, France's SPOT, Argentina's SAC-C, the European Space Agency's ENVISAT and ERS, India's IRS, Germany's Terra SAR, China's FY, SJ, and ZY satellites, Japan's ALOS, and, from the private sector, Geo-Eye-1, Digital Globe's Quickbird, and Qinetiq's TopSat. The charter also includes the Disaster Monitoring Constellation (DMC). On July 29, 2009, a Russian Dnepr Rocket launched two satellites, Spain's Deimos-1 and the United Kingdom's DMC-2, that are part of the multicountry DMC, which include Algeria's AISAT-1, Turkey's BilSAT (decommissioned in 2006), Nigeria's SAT-1, the United Kingdom's DMC, and China's Beijing-1.

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