Radar polarimetry and interferometry for remote sensing of boreal forest
School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2012-11-23
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Aalto University publication series DOCTORAL DISSERTATIONS, 153/2012
AbstractForest biomass is a key parameter of the global biosphere which is linked to many fields of research. Modeling addressing climate, ecology, and economics as well as many other prediction frameworks require an accurate assessment of global forest biomass. Methods for producing forest information are rapidly developing and traditional forest inventory by visual estimation has been gradually replaced by the use of airborne and spaceborne instruments. Nevertheless, the estimation of biomass on a global basis including boreal, temperate, and tropical forests, is still a major challenge. Among other spaceborne sensors, synthetic aperture radar (SAR) is one of the most suitable tools for large scale mapping and it has also been often used for forest mapping. However, commonly used backscattering intensity based methods do not provide a satisfactory accuracy for biomass estimation; hence, the scientific radar community has been developing more accurate means based on advanced SAR imaging and analyzing techniques, such as SAR polarimetry and interferometry. The work within this thesis contributes to this effort specifically in the field of remote sensing with the emphasis on SAR polarimetry and interferometry for boreal forest applications. The study concentrates on three main topics: polarimetric SAR image analysis, retrieval of forest height by means of SAR interferometry, and modeling of radar backscattering from trees. The main contributions of this work include a new effective approach in polarimetric target decomposition, novel polarimetric visualization schemes, an improved interferometric tree height estimation method suitable for boreal forest, interferometric tree height estimation capability demonstration for X-band, a novel method for relating SAR measurements to single tree scattering modeling, and taking the scattering modeling from a pine tree to the single needle level with accurate field models. Furthermore, the forest height estimation scheme proposed in this work potentially enables tree height estimation with existing spaceborne interferometric X-band SAR systems. The proposed method uses an interferometric coherence model and a ground elevation model to produce accurate tree height maps from single polarization interferometric SAR data. The method is demonstrated with airborne SAR measurements and will be tested in the near future with satellite data. Since tree height is related to forest biomass through tree allometry, tree height measurements from space would enable more accurate global forest biomass maps.
Supervising professorHallikainen, Martti, Prof.
radar, Synthetic Aperture Radar, SAR, SAR polarimetry, SAR interferometry, SAR polarimetric interferometry, InSAR, PolSAR, Pol-InSAR, boreal forest, scattering model, tree height, forest height, forest biomass
- [Publication 1]: Jaan Praks, Elise Colin-Koeniguer, Martti Hallikainen. Alternatives to target entropy and alpha angle in SAR polarimetry. IEEE Transactions on Geoscience and Remote Sensing, 47(7):2262-2274, July 2009.
- [Publication 2]: Jaan Praks, Florian Kugler, Konstantinos Papathanassiou, Irena Hajnsek, Martti Hallikainen. Height estimation of boreal forest: interferometric model-based inversion at L- and X-band versus HUTSCAT profiling scatterometer. IEEE Geoscience and Remote Sensing Letters, 4(3):466-470, July 2007.
- [Publication 3]: Jaan Praks, Oleg Antropov, Martti Hallikainen. LIDAR-aided SAR interferometry studies in boreal forest: scattering phase center and extinction coefficient at X- and L-band. IEEE Transactions on Geoscience and Remote Sensing, 50(10):3831-3843, October 2012.
- [Publication 4]: Jaan Praks, Jukka Sarvas, Martti Hallikainen, Jouni Pulliainen. Using multilook averaging for coherently modeled scattering from a pine tree at L-band. IEEE Geoscience and Remote Sensing Letters, 6(1):162-166, January 2009.
- [Publication 5]: Tommi Dufva, Jaan Praks, Seppo Järvenpää, Jukka Sarvas. Scattering model for a pine tree employing VIE with a broadband MLFMA and comparison to ICA. IEEE Transactions on Geoscience and Remote Sensing, 48(3):1119-1127, March 2010.