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An advanced radar technique to image forests in three dimensions has undergone an ESA-backed test campaign in Indonesia. A future space-based version could measure global biomass to sharpen the accuracy of climate change models.
The campaign, called the Second Indonesian Airborne Radar Experiment (INDREX-II), involved flying a test instrument called the Experimental Synthetic Aperture Radar (E-SAR), built by the German Aerospace Centre (DLR), in a Dornier-228 aircraft over eight test sites around Kalimantan on the island of Borneo.
The sites varied in character from pristine rainforest to coastal mangroves and oil palm and rubber plantations. They were also measured in detail on the ground to provide ‘ground truth’ for the radar results, around 200 Gigabytes of raw data having been gathered during three weeks of flights.
“We had already carried out tests in European forests,” explained INDREX-II team member Dirk Hoekman of the University of Wageningen. “We were able to extract the difference between the tree canopy and the forest floor - and from knowing tree height, we can use specially-developed algorithms to estimate forest biomass with a reasonable degree of certainty.
“What we needed to know was if the same was true of much denser tropical forests. So with ESA’s support and the co-operation of the Indonesian Ministry of Forestry we carried out this aerial survey over test sites that were also measured from the ground, in order to gather a sizeable tropical radar database. There is still a lot of analysis to be done, but early findings look promising.”
Hoekman added that the instrument also showed high sensitivity to flooded, burnt and logged forest areas, while Irena Hansek of DLR recounted that individual tall trees standing above the surrounding canopy could be detected.
An improved global picture of forests - which cover about 27% of the Earth’s total land surface - would have multiple uses. Woodland is an economic resource that is also central to the environment: as a haven for biodiversity, preventing soil erosion and flooding and influencing local climate.
Forests are also the most significant onshore stores of carbon, helping to absorb excess carbon dioxide that would otherwise increase global warming. So the Kyoto Protocol, about to come into force, allows nations with forested areas to set them against carbon emission. Accurate quantification of total forest biomass would provide verification for Kyoto and also shrink current uncertainties within climate change models.
The campaign took place during last November and December. Details of INDREX-II were presented during a workshop in ESA’s European Space Research Institute (ESRIN). Some 135 researchers from 27 countries attended the POLINSAR 2005 event, named for a relatively new radar technology called synthetic aperture radar (SAR) polarimetric interferometry (Pol-InSAR).
Participants in the weeklong workshop heard that other potential applications of the technology included monitoring of urban areas, ice fields and agriculture.
To read more about this story, click here: http://earthobservatory.nasa.gov/Newsroom/MediaAlerts/2005/2005020518306.html
Posted: Mar 02, 2005 9:42AM by Joe
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