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Browsing by Author "Wessels, K.J. (Konrad)"
Now showing items 1-18 of 18
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Mograbi, P.J. (Penelope); Erasmus, Barend Frederik Nel; Witkowski, E.F.T. (Ed); Asner, G.P. (Gregory); Wessels, K.J. (Konrad); Mathieu, Renaud; Knapp, D.E. (David); Martin, R.E. (Roberta); Main, Russell; Boldgiv, Bazartseren (Public Library of Science, 2015-05-13)Woody biomass dynamics are an expression of ecosystem function, yet biomass estimates do not provide information on the spatial distribution of woody vegetation within the vertical vegetation subcanopy. We demonstrate ...
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Kleynhans, Waldo; Olivier, Jan Corne; Wessels, K.J. (Konrad); Salmon, Brian Paxton; Van den Bergh, Frans; Steenkamp, Karen C. (Institute of Electrical and Electronics Engineers, 2011-05)A method for detecting land cover change using NDVI time series data derived from 500m MODIS satellite data is proposed. The algorithm acts as a per pixel change alarm and takes as input the NDVI time series of a 3x3 ...
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Mograbi, Penelope J.; Witkowski, Ed T.F.; Erasmus, Barend Frederik Nel; Asner, Gregory P.; Fisher, Jolene T.; Mathieu, Renaud; Wessels, K.J. (Konrad) (Wiley, 2019-01)Woody biomass remains the primary energy source for domestic use in the developing world, raising concerns about woodland sustainability. Yet woodland regenerative capacity and the adaptive response of harvesters to localised ...
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Mograbi, Penelope J.; Asner, Gregory P.; Witkowski, Ed T.F.; Erasmus, Barend Frederik Nel; Wessels, K.J. (Konrad); Mathieu, Renaud; Vaughn, Nicholas R. (Wiley, 2017-11)Humans have played a major role in altering savanna structure and function, and growing land-use pressure will only increase their influence on woody cover. Yet humans are often overlooked as ecological components. Both ...
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Main, Russell; Mathieu, Renaud; Kleynhans, Waldo; Wessels, K.J. (Konrad); Naidoo, Laven; Asner, Gregory P. (MDPI Publishing, 2016-08-17)Savanna ecosystems and their woody vegetation provide valuable resources and ecosystem services. Locally calibrated and cost effective estimates of these resources are required in order to satisfy commitments to monitor ...
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Improving land cover class separation using an extended Kalman filter on MODIS NDVI time-series data Kleynhans, Waldo; Olivier, Jan Corne; Wessels, K.J. (Konrad); Van den Bergh, Frans; Salmon, Brian Paxton; Steenkamp, Karen C. (Institute of Electrical and Electronics Engineers, 2009)It is proposed that the normalized difference vegetation index time series derived from Moderate Resolution Imaging Spectroradiometer satellite data can be modeled as a triply (mean, phase, and amplitude) modulated cosine ...
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Mathieu, Renaud; Wessels, K.J. (Konrad); Naidoo, Laven; Verstraete, Michel; Asner, Gregory; Main, Russell (MDPI Publishing, 2018-09)Forest structural data are essential for assessing biophysical processes and changes, and promoting sustainable forest management. For 18+ years, the Multi-Angle Imaging SpectroRadiometer (MISR) instrument has been ...
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Naidoo, Laven; Mathieu, Renaud; Main, Russell; Wessels, K.J. (Konrad); Asner, Gregory P. (Elsevier, 2016-10)Woody canopy cover (CC) is the simplesttwo dimensional metric for assessing the presence ofthe woody component in savannahs, but detailed validated maps are not currently available in southern African savannahs. A number ...
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Kleynhans, Waldo; Salmon, Brian Paxton; Olivier, Jan Corne; Van den Bergh, Frans; Wessels, K.J. (Konrad); Grobler, Trienko Lups; Steenkamp, Karen C. (Institute of Electrical and Electronics Engineers, 2012)Human settlement expansion is one of the most pervasive forms of land cover change in the Gauteng province of South Africa. A method for detecting new settlement developments in areas that are typically covered by natural ...
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Salmon, Brian Paxton; Kleynhans, Waldo; Van den Bergh, Frans; Olivier, Jan Corne; Marais, W.J.; Grobler, Trienko Lups; Wessels, K.J. (Konrad) (IEEE / Institute of Electrical and Electronics Engineers Incorporated, 2014-08)The extraction of information on land cover classes using unsupervised methods has always been of relevance to the remote sensing community. In this paper, a novel criterion is proposed, which extracts the inherent ...
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Kleynhans, Waldo; Salmon, Brian Paxton; Wessels, K.J. (Konrad); Olivier, Jan Corne (Elsevier, 2015-08)Recent development has identified the benefits of using hyper-temporal satellite time series data for land cover change detection and classification in South Africa. In particular, the monitoring of human settlement expansion ...
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Wessels, K.J. (Konrad); Van den Bergh, Frans; Roy, David P.; Salmon, Brian P.; Steenkamp, Karen C.; MacAlister, Bryan; Swanepoel, Derick; Jewitt, Debbie (MDPI Publishing, 2016-10-28)The paper evaluated the Landsat Automated Land Cover Update Mapping (LALCUM) system designed to rapidly update a land cover map to a desired nominal year using a pre-existing reference land cover map. The system uses the ...
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Naidoo, Laven; Mathieu, Renaud; Main, Russell; Kleynhans, Waldo; Wessels, K.J. (Konrad); Asner, Gregory P.; Leblon, Brigitte (Elsevier, 2015-07)Structural parameters of the woody component in African savannahs provide estimates of carbon stocks that are vital to the understanding of fuelwood reserves, which is the primary source of energy for 90% of households ...
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Salmon, Brian Paxton; Olivier, Jan Corne; Wessels, K.J. (Konrad); Kleynhans, Waldo; Van den Bergh, Frans; Steenkamp, Karen C. (Institute of Electrical and Electronics Engineers, 2011-06)An automated land cover change detection method is proposed that uses coarse spatial resolution hyper-temporal earth observation satellite time series data. The study compared three different unsupervised clustering ...
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Wessels, K.J. (Konrad); Colgan, M.S.; Erasmus, Barend Frederik Nel; Asner, G.P. (Gregory); Twine, W.C.; Mathieu, Renaud; Van Aardt, J.A.N.; Fisher, J.T. (Jolene); Smit, Izak P.J. (Institute of Physics, 2013-01-17)Wood and charcoal supply the majority of sub-Saharan Africa’s rural energy needs. The long-term supply of fuelwood is in jeopardy given high consumption rates. Using airborne light detection and ranging (LiDAR), we mapped ...
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Salmon, Brian Paxton; Olivier, Jan Corne; Kleynhans, Waldo; Wessels, K.J. (Konrad); Van den Bergh, Frans; Steenkamp, Karen C. (Elsevier, 2011-12)This paper presents a novel land cover change detection method that employs a sliding window over hyper-temporal multi-spectral images acquired from the 7 bands of the MODerate-resolution Imaging Spectroradiometer (MODIS) ...
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Tsela, Philemon Lehlohonolo; Wessels, K.J. (Konrad); Botai, Joel Ongego; Archibald, Sally; Swanepoel, Derick; Steenkamp, Karen C.; Frost, Philip (MDPI Publishing, 2014-02-04)The 500-m Moderate Resolution Imaging Spectroradiometer (MODIS) burned area products, MCD45A1, MCD64A1, and a merged product were validated across six study sites in South Africa using independently-derived Landsat burned-area ...
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Fisher, J.T. (Jolene); Witkowski, E.T.F. (Ed); Erasmus, Barend Frederik Nel; Mograbi, P.J. (Penelope); Asner, G.P. (Gregory); Van Aardt, J.A.N.; Wessels, K.J. (Konrad); Mathieu, Renaud (Wiley, 2015-07)QUESTION : Increasing population pressure, socio-economic development and associated natural resource use in savannas are resulting in large-scale land cover changes, which can be mapped using remote sensing. Is a ...
Now showing items 1-18 of 18