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Toward structural assessment of semi-arid African savannahs and woodlands: The potential of multitemporal polarimetric RADARSAT-2 fine beam images

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dc.contributor.author Mathieu, Renaud SA
dc.contributor.author Naidoo, Laven
dc.contributor.author Cho, Moses A
dc.contributor.author Leblon, B
dc.contributor.author Main, Russell S
dc.contributor.author Wessels, Konrad J
dc.contributor.author Asner, GP
dc.contributor.author Buckley, J
dc.contributor.author Van Aardt, J
dc.contributor.author Erasmus, BFN
dc.contributor.author Smit, IPJ
dc.date.accessioned 2014-03-11T08:17:22Z
dc.date.available 2014-03-11T08:17:22Z
dc.date.issued 2013-11
dc.identifier.citation Mathieu, R.S.A., Naidoo, L., Cho, M.A., Leblon, B., Main, R., Wessels, K.J., Asner, G.P., Buckley, J., Van Aardt, J., Erasmus, B.F.N. and Smit, I.P.J. 2013. Toward structural assessment of semi-arid African savannahs and woodlands: The potential of multitemporal polarimetric RADARSAT-2 fine beam images. Remote Sensing of Environment, vol. 138, pp 215-231 en_US
dc.identifier.issn 0034-4257
dc.identifier.uri http://ac.els-cdn.com/S003442571300223X/1-s2.0-S003442571300223X-main.pdf?_tid=00388c1e-a5e7-11e3-b4c7-00000aacb360&acdnat=1394189911_15e57fb8dc360747edba85fcedf70472
dc.identifier.uri http://hdl.handle.net/10204/7279
dc.identifier.uri https://www.sciencedirect.com/science/article/abs/pii/S003442571300223X
dc.identifier.uri https://doi.org/10.1016/j.rse.2013.07.011
dc.description Copyright: 2013 Elsevier. This is an ABSTRACT ONLY. The definitive version is published in Remote Sensing of Environment, vol. 138, pp 215-231 en_US
dc.description.abstract Woody vegetation structure affects wildlife habitat selection and species diversity for a wide range of taxa, and at a variety of scales. Indicators of woody structure can indicate the spatio-temporal variability of biodiversity, species occurrence and assemblages. Woody cover is the simplest and most widely used structural metric. Combined with the vegetation height, it provides a volumetric indicator, which is more informative, and is simple to calculate. We therefore assessed the utility of multitemporal polarimetric RADARSAT-2 C-band imagery to map measures of woody volumetric indices in Lowveld savannahs, in the vicinity of the Kruger National Park, South Africa. RADARSAT-2 Quad-Pol fine beam images were acquired at three key phenological stages of the seasonal savannah cycle: i) wet (summer), ii) dry (winter), and iii) end of wet (autumn). Multi-polarized band intensities (C-HH, C-HV, and C-VV, with V = vertical and H = horizontal) and polarimetric decomposition variables (Freeman–Durden, Cloude–Pottier, and Van Zyl) were derived from the SAR images and used to predict structural metrics (woody canopy cover, cylindrical woody volume, and woody canopy volume, see definition in Section 3.3) derived from 1.1 m LiDAR strips acquired across the study area, and coinciding with 12% of the SAR dataset. The best single relationship (R(sup2) = 0.66) was obtained between the cross-polarized HV intensity band and the total canopy volume (TCV). In terms of the seasonality, the best results were obtained using the SAR imagery from the dry season when most woody plants have lost their leaves and the grass-soil layer was dry. Validation outputs of best predictive models for TCV, at the individual season level, yielded an R(sup2) of 0.67, a Standard Error of Prediction (SEP) of 39%, and consisted of the SAR parameters: C-HH, C-HV, C-VV, and Freeman–Durden decomposition parameters. At the multi-seasonal level, the best predictive models for TCV yielded an R(sup2) of 0.75, a SEP of 35%, and comprised of the same variables but for all three seasons. The C-band SAR data thus provided encouraging results in open, semi-arid savannahs and hint at larger area structural assessments than is possible with LiDAR sensors alone. The combined use of C-band and L-band (ALOS-Palsar 2) should also be investigated. en_US
dc.language.iso en en_US
dc.publisher Elsevier en_US
dc.relation.ispartofseries Workflow;12234
dc.subject Semi-arid African savannahs en_US
dc.subject Remote sensing en_US
dc.subject Environmental management en_US
dc.subject Woody vegetation structures en_US
dc.subject Polarimetry en_US
dc.title Toward structural assessment of semi-arid African savannahs and woodlands: The potential of multitemporal polarimetric RADARSAT-2 fine beam images en_US
dc.type Article en_US
dc.identifier.apacitation Mathieu, R. S., Naidoo, L., Cho, M. A., Leblon, B., Main, R. S., Wessels, K. J., ... Smit, I. (2013). Toward structural assessment of semi-arid African savannahs and woodlands: The potential of multitemporal polarimetric RADARSAT-2 fine beam images. http://hdl.handle.net/10204/7279 en_ZA
dc.identifier.chicagocitation Mathieu, Renaud SA, Laven Naidoo, Moses A Cho, B Leblon, Russel S Main, Konrad J Wessels, GP Asner, et al "Toward structural assessment of semi-arid African savannahs and woodlands: The potential of multitemporal polarimetric RADARSAT-2 fine beam images." (2013) http://hdl.handle.net/10204/7279 en_ZA
dc.identifier.vancouvercitation Mathieu RS, Naidoo L, Cho MA, Leblon B, Main RS, Wessels KJ, et al. Toward structural assessment of semi-arid African savannahs and woodlands: The potential of multitemporal polarimetric RADARSAT-2 fine beam images. 2013; http://hdl.handle.net/10204/7279. en_ZA
dc.identifier.ris TY - Article AU - Mathieu, Renaud SA AU - Naidoo, Laven AU - Cho, Moses A AU - Leblon, B AU - Main, Russel S AU - Wessels, Konrad J AU - Asner, GP AU - Buckley, J AU - Van Aardt, J AU - Erasmus, BFN AU - Smit, IPJ AB - Woody vegetation structure affects wildlife habitat selection and species diversity for a wide range of taxa, and at a variety of scales. Indicators of woody structure can indicate the spatio-temporal variability of biodiversity, species occurrence and assemblages. Woody cover is the simplest and most widely used structural metric. Combined with the vegetation height, it provides a volumetric indicator, which is more informative, and is simple to calculate. We therefore assessed the utility of multitemporal polarimetric RADARSAT-2 C-band imagery to map measures of woody volumetric indices in Lowveld savannahs, in the vicinity of the Kruger National Park, South Africa. RADARSAT-2 Quad-Pol fine beam images were acquired at three key phenological stages of the seasonal savannah cycle: i) wet (summer), ii) dry (winter), and iii) end of wet (autumn). Multi-polarized band intensities (C-HH, C-HV, and C-VV, with V = vertical and H = horizontal) and polarimetric decomposition variables (Freeman–Durden, Cloude–Pottier, and Van Zyl) were derived from the SAR images and used to predict structural metrics (woody canopy cover, cylindrical woody volume, and woody canopy volume, see definition in Section 3.3) derived from 1.1 m LiDAR strips acquired across the study area, and coinciding with 12% of the SAR dataset. The best single relationship (R(sup2) = 0.66) was obtained between the cross-polarized HV intensity band and the total canopy volume (TCV). In terms of the seasonality, the best results were obtained using the SAR imagery from the dry season when most woody plants have lost their leaves and the grass-soil layer was dry. Validation outputs of best predictive models for TCV, at the individual season level, yielded an R(sup2) of 0.67, a Standard Error of Prediction (SEP) of 39%, and consisted of the SAR parameters: C-HH, C-HV, C-VV, and Freeman–Durden decomposition parameters. At the multi-seasonal level, the best predictive models for TCV yielded an R(sup2) of 0.75, a SEP of 35%, and comprised of the same variables but for all three seasons. The C-band SAR data thus provided encouraging results in open, semi-arid savannahs and hint at larger area structural assessments than is possible with LiDAR sensors alone. The combined use of C-band and L-band (ALOS-Palsar 2) should also be investigated. DA - 2013-11 DB - ResearchSpace DP - CSIR KW - Semi-arid African savannahs KW - Remote sensing KW - Environmental management KW - Woody vegetation structures KW - Polarimetry LK - https://researchspace.csir.co.za PY - 2013 SM - 0034-4257 T1 - Toward structural assessment of semi-arid African savannahs and woodlands: The potential of multitemporal polarimetric RADARSAT-2 fine beam images TI - Toward structural assessment of semi-arid African savannahs and woodlands: The potential of multitemporal polarimetric RADARSAT-2 fine beam images UR - http://hdl.handle.net/10204/7279 ER - en_ZA


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