Proceedings Covers Remote Sensing of Natural Disasters

Engineers are working on better forecasting methods

5 October 2012

proceed Photo: IEEE

Another in a series of articles in The Institute highlighting the special issues being published by Proceedings of the IEEE in celebration of the journal’s 100th anniversary.

Are we seeing more frequent and intense natural disasters lately? It’s a question scientists have been contemplating for years. But one thing is for sure: Disasters are costly—in human lives, economic impact, ecosystem damage, and more.

The U.S. Geological Survey reports that globally there have been more than 17 earthquakes each year for the last 18 years that were a magnitude 7 or higher. This year there were devastating earthquakes in Mexico, historic flooding in China and India, and ravaging fires and droughts across the United States. In addition, in recent years oil spills and other manmade disasters have wreaked havoc on the environment.

But last year was most noteworthy. Dubbed by many experts as the “Year of Extreme Weather,” 2011 was the costliest on record, with 12 weather- and climate-related disasters resulting in US $380 billion in damage around the world. The tsunami generated by the magnitude 9 earthquake in Japan led to more than 15 000 deaths, unprecedented social and economic impacts, and a nuclear disaster likely to affect the ecosystem for years. A magnitude 6.3 earthquake in Christchurch, New Zealand, led to 185 fatalities and extensive damage. And a rare EF-5 tornado, with winds topping 321 kilometers per hour, struck Joplin, Mo., killing 158 people. It was the deadliest tornado to strike the United States since modern recordkeeping began in 1950.

Such natural hazards “may well increase in both frequency and intensity under projected climate change,” and their impact might be greater because of human activities, Kun-Shan Chen, Sebastiano B. Serpico, and James A. Smith write in the introduction to the October 2012 Proceedings of the IEEE. The issue, which covers remote sensing of natural disasters, focuses on ways technology might help forecast them and ultimately lessen their impact. “The remote sensing community is actively and quickly moving toward more advanced methodologies, linking remote sensing with in situ measurements and ancillary data for more precise mapping, faster analysis, and more effective forecasting and data delivery,” the authors write.

The issue’s 11 papers cover some of the latest technologies used on early warning systems for oil spills, earthquakes, tsunamis, volcanic eruptions, floods, landslides, and more.

The first paper, “ASTER Satellite Observations for International Disaster Management,” covers the Advanced Spaceborne Thermal Emission and Reflection Radiometer, an imaging instrument on board NASA’s Earth Observation System. Data from the satellite are used to create detailed maps of surface temperature, reflectance (the fraction of incoming solar radiation reflected from Earth’s surface), and ground elevation. The maps are used to observe the effects of disasters. ASTER is a cooperative effort of NASA; Japan’s Ministry of Economy, Trade, and Industry; and Japan Space Systems.

“Human Sensor Networks for Improved Modeling of Natural and Human-Induced Disasters” describes an approach that uses data from social media, geophysical models, and satellite observations to model disasters’ effects. The authors describe how such a method could have been used for the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. They gathered mentions of oil sightings from the photo-sharing social-media website Flickr, pinpointed where the sightings occurred, and then entered the data into oil-spill modeling software. The authors say this method of data collection resulted in better estimates than the more traditional techniques based on the rate of flow from the spill.

“Mapping Geo-Hazard by Satellite Radar Interferometry” discusses the application of satellite interferometric synthetic aperture radar (InSAR) to chart earthquakes and landslides in Taiwan and Vietnam, which are particularly prone to such events. InSAR can measure centimeter-scale changes in land deformation over days or years. The authors applied InSAR to analyze the effects of a magnitude 7.6 earthquake in 1999 that killed more than 2500 people in Taiwan, as well as other disasters in the region.

Two papers discuss the advantages of using polarimetric SAR (PolSAR) to observe damage. PolSAR uses the random polarization SAR returns from surfaces, such as grass or sand, over time to detect small changes invisible to optical monitoring systems. “Disaster Monitoring by Fully Polarimetric SAR DATA Acquired With ALOS-PALSAR” focuses on the use of a target-decomposition model to analyze volcanic activity, snow accumulation, landslides, and tsunamis. The author states that such events cause changes in scattering power, which is the loss experienced by an electromagnetic wave in a medium in which it is passing due to reflections and distortions by particles in the medium. He says it is easy to spot the changes in polarimetric decomposed images because of differences in color.

The second paper, “Polarimetric SAR Analysis of Tsunami Damage Following the March 11th East Japan Earthquake,” includes detailed mapping and analysis of the 2011 event from satellite imagery. The authors studied the damage sensed by several satellite systems, including ALOS/PALSAR and Pi-SAR2. The analysis is a more efficient method of observing damage than the widely used SAR interferometry techniques, they say, because damage can be detected with a single PolSAR observation. Several different images can be constructed using PolSAR methods, thus yielding more information from a single PolSAR observation than is possible with other observational methods.

Other papers in the issue cover volcanic eruptions, oil spills, and flooding. “Remote Sensing of Volcanic Hazards and Their Precursors” explores combining interferometric SAR and spectroradiometry. Interferometric SAR is used to detect displacement of a volcano’s surface because of magma movement, and spectroradiometry senses and then monitors an eruption by detecting hot spots.

“Remote Sensing of Ocean Oil-Spill Pollution” describes methods that combine satellite monitoring, aircraft surveillance, and spaceborne SAR to check for possible oil spills. And “Information Extraction From Remote Sensing Images for Flood Monitoring and Risk Assessment” estimates potential damage.

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