University of Twente Student Theses


The potential of synthetic aperture radar for the detection of forest degradation signs in Congo-Brazzaville

Ogbodo, John Agbo (2013) The potential of synthetic aperture radar for the detection of forest degradation signs in Congo-Brazzaville.

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Abstract:Tropical forest cover is declining in many parts of the world. This process is of global concern, as it is considered to be one of the main drivers of climate change. Radar remote sensing is useful to monitor forest coverage since the presence of clouds often limits a continuous and periodic monitoring by optical sensors. The overall objective of this study was to assess the potential of very high (1m – 3m) and medium (8m – 30m) resolution synthetic aperture radar imagery for identifying forest degradation signs. This was done with a view as to contribute to the development of alternative monitoring strategies in support of the monitoring, reporting, and verification (MRV) framework of UN-REDD+. The study area was a 20x10 km site in the tropical forest region of southern Congo-Brazzaville. The major approach adopted in this study was visual interpretation. Forest and non-forest could be clearly separated in VHR TerraSAR-X (SpotLight and StripMap) and on 8m RADARSAT Multi-Look Fine imagery, while not on ENVISAT ASAR Image Mode imagery. Logging roads were only visible on 1m TerraSAR-X SpotLight and 3m TerraSAR-X StripMap imagery. Both of these data sources and RADARSAT Multi-Look Fine images could detect clearcuts in dense to open canopy forest types. To assess whether the detection of such clearcuts can be automated, and thus applied more easily to larger regions, a simple automated approach was developed. The approach consisting of thresholding and subsequent majority filtering proved effective in separating most clearcuts in coarse canopied forest. This study concludes that the detection of logging roads by SAR requires spatial resolutions below 5m, while clearcuts are detectable with 10m resolution. It was found that the viewing geometry of the SAR data acquisitions has a strong effect on the possibility to visually detect forest degradation signs. For monitoring purposes, repeated monitoring using the same satellite sensor and viewing geometry is therefore recommended. Given the reasonably low-price and good coverage, TerraSAR StripMap acquisitions are recommended for further studies towards monitoring options in the framework of REDD+. Keywords: clearcut, forest degradation, logging roads, REDD+, SAR, viewing geometry
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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