| 1. |
- Askne, Jan, 1936, et al.
(author)
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Model-Based Biomass Estimation of a Hemi-Boreal Forest from Multitemporal TanDEM-X Acquisitions
- 2013
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In: Remote Sensing. - : MDPI AG. - 2072-4292. ; 5:11, s. 5574-5597
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Journal article (peer-reviewed)abstract
- Above-ground forest biomass is a significant variable in the terrestrial carbon budget, but is still estimated with relatively large uncertainty. Remote sensing methods can improve the characterization of the spatial distribution and estimation accuracy of biomass; in this respect, it is important to examine the potential offered by new sensors. To assess the contribution of the TanDEM-X mission, eighteen interferometric Synthetic Aperture Radar (SAR) image pairs acquired over the hemi-boreal test site of Remningstorp in Sweden were investigated. Three models were used for interpretation of TanDEM-X signatures and above-ground biomass retrieval: Interferometric Water Cloud Model (IWCM), Random Volume over Ground (RVoG) model, and a simple model based on penetration depth (PD). All use an allometric expression to relate above-ground biomass to forest height measured by TanDEM-X. The retrieval was assessed on 201 forest stands with a minimum size of 1 ha, and ranging from 6 to 267 Mg/ha (mean biomass of 105 Mg/ha) equally divided into a model training dataset and a validation test dataset. Biomass retrieved using the IWCM resulted in a Root Mean Square Error (RMSE) between 17% and 33%, depending on acquisition date and image acquisition geometry (angle of incidence, interferometric baseline, and orbit type). The RMSE in the case of the RVoG and the PD models were slightly higher. A multitemporal estimate of the above-ground biomass using all eighteen acquisitions resulted in an RMSE of 16% with R-2 = 0.93. These results prove the capability of TanDEM-X interferometric data to estimate forest aboveground biomass in the boreal zone.
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| 2. |
- Blomberg, Erik, 1987, et al.
(author)
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P-band Polarimetric Model of Vertical Tree Stems on Sloping Ground
- 2014
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In: Joint 2014 IEEE International Geoscience and Remote Sensing Symposium, IGARSS 2014 and the 35th Canadian Symposium on Remote Sensing, CSRS 2014; Quebec Convention CentreQuebec City; Canada; 13 July 2014 through 18 July 2014. - 9781479957750 ; , s. 80-83
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Conference paper (peer-reviewed)abstract
- A fully polarimetric model is implemented to simulate backscatter from boreal forest. The aim is to correct for topography on a sub-stand level during the recovery of forest properties from P-band SAR data, specifically directed at the upcoming BIOMASS mission. The model incorporates the direct, double-bounce and triple-bounce scattering from tree stems on a sloping ground. Topography is introduced by assigning an independent and arbitrarily oriented local ground plane to each tree. Simulated SAR images are produced from in-situ measurements and a high resolution digital topography model (DTM) based on LiDAR data. These were obtained during BioSAR 2010 together with the corresponding SAR images, which are used for validation.
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| 3. |
- Eriksson, Leif, 1970, et al.
(author)
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Backscatter signatures of wind-thrown forest in satellite SAR images
- 2012
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In: International Geoscience and Remote Sensing Symposium (IGARSS). - 2153-6996 .- 2153-7003. - 9781467311588 ; , s. 6435-6438
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Conference paper (peer-reviewed)abstract
- Two field experiments have been conducted in Sweden to allow an evaluation of the backscatter signatures of wind-thrown forest from L-band, C-band and X-band Synthetic Aperture Radar. When the trees are felled the backscattered signal from TerraSAR-X (X-band) increase with about 1.5 dB, while for ALOS PALSAR (L-band) a decrease with the same amount is observed. Radar images with fine spatial resolution also show shadowing effects that should be possible to use for identification of storm felled forest.
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| 4. |
- Fransson, Johan E.S., et al.
(author)
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Mapping of wind-thrown forests using satellite SAR images
- 2010
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In: Proceedings of IGARSS 2010 Symposium, Remote Sensing: Global Vision for Local Action, Honolulu, Hawaii, USA, 25-30 July, 2010. - 9781424495641 ; , s. 1242-1245, s. 1242-1245
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Conference paper (other academic/artistic)abstract
- The study focuses on investigation and evaluation of wind- thrown forest mapping using satellite remotely sensed data from three synthetic aperture radar (SAR) sensors. The study is carried out at Remningstorp, a test site in the south of Sweden dominated by coniferous forest, where trees were manual felled to simulate wind-thrown forest. The satellite data consisted of time series of HH polarized SAR images acquired by the Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR), Radarsat-2 (C-band) and TerraSAR-X (X- band). The results from visual interpretation of SAR images acquired before and after the simulated wind-throw together with corresponding ratio images show that ALOS PALSAR HH polarized intensity images are not able to detect wind- thrown forest, probably due to too coarse spatial resolution. In contrast, the wind-thrown forest is clearly visible in the Radarsat-2 and TerraSAR-X HH polarized images, implying that it may be possible to develop a new application using these SAR data for mapping of wind-thrown forests.
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| 5. |
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| 6. |
- Sandberg, Gustaf, 1982, et al.
(author)
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Impact and modeling of topographic effects on P-band SAR backscatter from boreal forests
- 2011
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In: Proceedings of IGARSS 2011 Symposium, Vancouver, Canada, 24-29 July, 2011. - 9781457710056 ; , s. 3522-3525
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Conference paper (other academic/artistic)abstract
- P-band SAR backscatter has been proven to be useful for forest biomass prediction. However, there is a need for further studies on effects of topography on P-band backscatter. In this paper, two prediction models for backscatter are evaluated, one using only biomass as predictor and one which also includes topographic corrections. Data from the BioSAR 2007 and BioSAR 2008 campaigns are used to evaluate the models. A multi-scale error model which is able to handle data from several imaging directions is used. For HH, the slope correction on stand level used in this paper is unable to correct for topographic effects. This is consistent with previous results that within stand topographic variability has a significant impact on HH P-band backscatter. For HV and VV, the model which considers topography gives lower prediction errors than the model which does not include topography. Moreover, for these polarizations topographic the correction strongly reduce the variability in backscatter measurements between imaging directions for stands with ground slopes larger than about 5 degrees.
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| 7. |
- Sandberg, Gustaf, 1982, et al.
(author)
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Measurements of forest change using P-band SAR backscatter
- 2012
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In: International Geoscience and Remote Sensing Symposium (IGARSS). - 2153-6996 .- 2153-7003. - 9781467311588 ; , s. 1652-1655
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Conference paper (peer-reviewed)abstract
- Using data from the recent BioSAR 2007 and BioSAR 2010 campaigns, it has for the first time been possible to measure forest biomass change using P-band SAR data. Regression models based on backscatter change have been developed using reference data derived from high density laser scanning data. The models were evaluated for six areas with detailed in-situ measurements, for which the maximum biomass loss and growth was 30% and 20%, respectively. For the best model the coefficients of determination was 55-89%. This result suggests that not only clear cuts but also forest growth and thinning can be measured using P-band SAR backscatter.
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| 10. |
- Soja, Maciej, 1985, et al.
(author)
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Digital Canopy Model Estimation from TanDEM-X Interferometry using High-Resolution Lidar DEM
- 2013
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In: Proceedings of IEEE Geoscience and Remote Sensing Symposium (IGARSS), 21-26 July 2013. - 9781479911141 ; , s. 165-168
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Conference paper (peer-reviewed)abstract
- Interferometric TanDEM-X data are used together with high-resolution, airborne lidar-derived digital elevation models (DEMs) to produce digital canopy models (DCMs) for the boreal forests of Remningstorp and Krycklan, situated in southern and northern Sweden, respectively. An overview of interferometric data processing is given. First results showing the potential of TanDEM-X-based forest canopy mapping are presented. It is concluded that baselines giving height-of-ambiguity values in the order of 50-80 meters are preferable, although factors such as angle of incidence and along-track baseline are also of importance. Clear-cuts can easily be detected thanks to the high resolution of TanDEM-X imagery. Seasonal variations of scattering height are most visible for deciduous trees, where the scattering height is significantly lower in the winter, probably due to the lack of leaves. © 2013 IEEE.
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