22 December 2011

Remote sensing at work: Organic crops, wetlands monitoring, coal mining, and more

Remote sensing technologies provide solutions to numerous and varied problems around the world. Here are six recent applications:

How can a remote yet vital wetland be monitored?

Problem: The socio-economically vital Sudd wetland in southern Sudan’s Nile River swamps is threatened by overgrazing and by loss of vegetation during the wet season. But its remoteness and inaccessibility due to civil war prevents field studies.

Solution: Using geospatial data-authoring software to quantify wetland cover changes, researchers from Ain Shams University in Cairo developed a process to interpret Landsat-generated imagery, map land-cover types and compare the images to produce change-detection maps. Read more in the team’s article in the SPIE Newsroom


What happens to land stability after coal is mined?

Problem: Extracting coal from underground mines generally leads to subsidence of the overlaying land within days or sometimes years. Local governments need information about land subsidence to ensure that miners are staying within permitted areas and to monitor environmental effects. However, conventional field monitoring is expensive and time-consuming, and mountainous or inhospitable terrain can make it difficult or even impossible.

Solution: Researchers from the National Remote Sensing Center of China and the Center for Earth Observation and Digital Earth of the Chinese Academy of Sciences have reported on a method of monitoring land subsidence with multi-band differential synthetic aperture radar interferometry (DInSAR). Air- or spaceborne detectors scan Earth's surface with radio waves to create a topographical map of the ground, and DInSAR compares SAR interferometry data taken hours, days or years apart to show subtle topographical changes. Read the team’s article in the SPIE Newsroom.

Are those crops organic?

Problem: Organic agriculture provides healthy food and protects the environment by avoiding the widespread dissemination of chemicals. Products may be labeled “organic” only if they are produced according to established standards, undergo an evaluation and pass a yearly inspection.

Solution: Because conventional and organic crops are treated differently, their characteristics are also different. The European Space Agency (ESA) is working with Ecocert, an organic certification organization, to use satellite images to spot these differences and support the certification process. This new space-based approach for organic farming was developed by Keyobs, VISTA and the University of Li├Ęge under the guidance of Ecocert, as part of an ESA Earth Observation Market Development project. Read more in the SPIE Professional article.

From Prague

Among papers presented at SPIE Remote Sensing in Prague this fall that examined the oceans were the following reports from the Mediterranean Sea, the Gulf of Mexico and the Pacific Ocean. (The papers were published in the SPIE Digital Library, with open-access abstracts and full papers available by subscription, rental or pay-per-view.)

Is surface runoff decreasing ocean fish stocks?

Problem: Surface runoff from land can affect ocean fish stocks by inhibiting the vitality of chlorophyll in phytoplankton in the water.

Solution: A team from the University of Malta and the European Commission Joint Research Centre statistically compared ocean color values from satellites with values collected in the field. Ocean color can be used to gauge the productivity of a marine area since it is the measure of suspended chlorophyll pigment. Chlorophyll is found in the microscopic phytoplankton which are the basis of marine food webs. Access the team’s paper “A first attempt at testing correlation between MODIS ocean colour data and in situ chlorophyll -- measurements within Maltese coastal waters” in the SPIE Digital Library, and read the Times of Malta article on the work.

How does an oil spill affect fish reproduction?

Problem: In the Gulf of Mexico, oil and dispersant chemicals left after the Deepwater Horizon spill covered critical fish spawning and larval areas. Oil on the sea surface and the timing of its occurrence likely impacted the developing eggs and larvae of bluefin tuna, blue marlin and other fishes whose eggs concentrate in the sea surface microlayer (SML) ? the topmost millimeter. The SML also concentrates petroleum, petroleum-derived hydrocarbons, tar, pesticides, polychlorinated biphenyls (PCBs), heavy metals and plastics. Exposure to oil and oil dispersants causes acute toxicity, narcosis and eventual death in marine fish larvae. Surface oil has been detected in 100% of the northernmost whale shark sightings, 32.8 % of the bluefin tuna spawning area and 38 % of the blue marlin larval area.

Solution: Researchers from Ocean Research and Conservation Association and the Florida Institute of Technology used biogeographical analyses to gain insights on these impacts. The research team georeferenced historical ichthyoplankton surveys and published literature to map targeted spawning and larval areas in the Gulf with daily satellite-derived images. Read more about the work in their paper “Potential impacts of the Deepwater Horizon oil spill on large pelagic fishes.”

What damage did the earthquake and tsunami cause?

Problem: Depending on its magnitude and location, an earthquake may have unexpectedly complex impacts, and affected areas may be difficult to access in order to assess the damage.

Solution: After the 9.0-magnitude earthquake off the Pacific Coast of Japan on 11 March 2011, the Japan Aerospace Exploration Agency (JAXA) provided images acquired by the Advanced Land Observing Satellite (ALOS) to national and local governments of Japan, to aid in disaster recovery and restoration. JAXA also received and analyzed more than 5,000 scenes via the International Disaster Charter and Sentinel Asia, and supported the governments through its Disaster Management Support Systems Office. Read more about the JAXA team’s efforts in their paper “Disaster monitoring for Japan Earthquake with satellites by JAXA.”

Remote sensing is indeed at work around the world, monitoring impacts of human activity and natural phenomena to help improve quality of life.

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