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- Askne, Jan, 1936, et al.
(författare)
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L-Band Observations of Boreal Forest Stem Volume
- 2004
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Ingår i: Proceedings of the 23rd EARSeL Symposium on Remote Sensing in Transition, Millpress, 'Rotterdam, ed. R. Goassens. ; , s. 159-
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Konferensbidrag (refereegranskat)
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- Eriksson, Leif, 1970, et al.
(författare)
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ALOS PALSAR Calibration and Validation Results from Sweden
- 2007
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Ingår i: IEEE Geoscience and Remote Sensing Symposium (IGARSS 2007), Barcelona, Spain, July 23-27, 2007. ; DOI: 10.1109/IGARSS.2007.4423115, s. 1589-1592
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In 2006 calibration activities for ALOS PALSAR wereconducted in Sweden. Four five-metre trihedral corner reflectorsand three smaller dihedral reflectors were deployed and operatedduring eight months. 23 PALSAR scenes were acquired over thecalibration site allowing an evaluation of the quality and temporalstability of the data. Results show that the co-polarized datahave been stable during the whole calibration period with variationsin the trihedral responses lower than 0.7 dB. The measuredresolution in azimuth was 4.4 m and in slant range 4.7 m forsingle polarization images and 9.5 m for polarimetric data. Forthe cross-polarized data large variations in the dihedral responseswere found. It is assumed that this is caused by a larger sensitivityto pointing errors. For the polarimetric data, estimation ofFaraday rotation gave values ranging from 0.1º to 3º.
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| 8. |
- Folkesson, Klas, 1976, et al.
(författare)
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Model-based compensation of topography effects for improved stem volume retrieval from CARABAS-II VHF-band SAR images
- 2009
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Ingår i: IEEE Transactions on Geoscience and Remote Sensing. - 0196-2892 .- 1558-0644. ; 47:4, s. 1045-1055
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Tidskriftsartikel (refereegranskat)abstract
- A limiting factor that has been identified for stem-volume retrieval in coniferous forests using VHF synthetic aperture radar is that the backscatter varies depending on ground topography. On sloping ground, the backscatter from a forest is reduced, since the dominant groundtrunk double-bounce scattering mechanism is changed. This leads to underestimation of stem volume, and the variations caused by topography can obscure real variations in stem volume. By using multiple images acquired with different flight headings and combining the image information with ground-topography data in a model-based inversion method, we are able to compensate for the ground-topography influence on the backscatter. The inversion method is based on image segmentation and the optimal estimation method. Using four or more images from the CARABAS-II system and a coarse digital elevation model with 50-m horizontal grid, the stem volume can be retrieved with an average root-mean-square error (rmse) of less than 60 $\hbox{m}^{3}\hbox{ha}^{-1}$ for stem volumes in range of 80700 $\hbox{m}^{3}\hbox{ha}^{-1}$ (in terms of above-ground biomass, this is equivalent to an rmse of less than 40 $\hbox{ton} \cdot\hbox{ha}^{-1}$ over the range of 50400 $\hbox{ton} \cdot\hbox{ha}^{-1}$). The retrieval accuracy is similar to that previously obtained for similar forests standing on flat and horizontal ground.
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| 9. |
- Folkesson, Klas, 1976, et al.
(författare)
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Stem volume retrieval at stand level using multiple low-frequency SAR images
- 2003
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Ingår i: IEEE Geoscience and Remote Sensing Symposium (IGARSS), Toulouse, France, 21-25 July. - 0780379292 ; IV, s. 2556-8
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper the ground slope effect on stem volume retrieval from VHF-band SAR images has been studied using multiple co-registered images acquired from different flight headings. Accurate measurements of the topography were used as additional input data to a model of the backscatter amplitude variation with ground slope and aspect angle. Modeling this topographical effect on the radar backscatter provides a base for improvement of the stem volume retrieval
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