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Browsing by Author "Mathieu, Renaud SA"

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Impact of communal land use and conservation on woody vegetation structure in the Lowveld savannas of South Africa

Author: Wessels, Konrad J ; Mathieu, Renaud SA ; Erasmus, BFN ; Asner, GP ; Smit, IPJ ; Van Aardt, JAN ; Main, Russell S ; Fisher, J ; Marais, W ; Kennedy-Bowdoin, T ; Knapp, DE ; Emerson, R ; Jacobson, J Date: Jan 2011 Millions of people rely on savannas for ecosystem services, such as the provision of grazing and fuel wood, so it is important to determine the extent to which utilization affects woody vegetation resources. Using airborne LiDAR from the ... Read more
Impact of communal land use and conservation on woody vegetation structure in the Lowveld savannas of South Africa – Lidar results

Author: Wessels, Konrad J ; Mathieu, Renaud SA ; Erasmus, BFN ; Asner, GP ; Smit, IPJ ; Van Aardt, JAN ; Main, Russell S ; Fisher, J Date: Apr 2011 People in the rural, communal areas of South Africa rely on live fuel wood for more than 90% of their energy requirements. Using airborne lidar from the Carnegie Airborne Observatory (CAO) the authors compared tree canopy cover and height ... Read more
Impacts of communal fuelwood extraction on lidar-estimated biomass patterns of savanna woodlands

Author: Wessels, Konrad J ; Erasmus, BFN ; Colgan, M ; Asner, GP ; Mathieu, Renaud SA ; Twine, W ; Van Aardt, JAN ; Smit, I Date: Jul 2012 Approximately 54% of rural households in South Africa continue to use wood as their main source of energy, mainly for cooking and heating. The provision of biomass by savanna woodlands is thus of considerable value to rural households and ... Read more
Improving discrimination of savanna tree species through a multiple endmember spectral-angle-mapper (SAM) approach: canopy level analysis

Author: Cho, Moses A ; Debba, Pravesh ; Mathieu, Renaud SA ; Naidoo, Laven ; Van Aardt, J ; Asner, G Date: Nov 2010 Differences in within-species phenology and structure are controlled by genetic variation, as well as topography, edaphic properties, and climatic variables across the landscape and present important challenges to species differentiation with ... Read more
Indirect estimation of structural parameters in South African forests using MISR-HR and LiDAR remote sensing data

Author: Mahlangu, Precious N ; Mathieu, Renaud SA ; Wessels, Konrad J ; Naidoo, Laven ; Verstraete, M ; Asner, G ; Main, Russell S Date: Sep 2018 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 observing the land surface ... Read more
Integrating environmental and in situ hyperspectral remote sensing variables for grass nitrogen estimation in savannah ecosystems

Author: Ramoelo, Abel ; Cho, Moses A ; Mathieu, Renaud SA ; Skidmore, AK ; Schlerf, M ; Heitkonig, IMA ; Prins, HHT Date: Apr 2011 Information about the distribution of grass nitrogen (N) concentration is crucial in understanding rangeland vitality and facilitates effective management of wildlife and livestock. A challenge in estimating grass N concentration using remote ... Read more
Integrating remote sensing and ancillary data for regional ecosystem assessment: eucalyptus grandis agro-system in kwazulu-Natal, South Africa

Author: Cho, Moses A ; Van Aardt, J ; Main, Russell S ; Majeke, B ; Mathieu, Renaud SA ; Norris-Rogers, M ; Du Plessis, M ; Ramoelo, Abel Date: Jul 2009 The study demonstrates that the integration of remote sensing and in situ data could be important in providing more accurate estimates of E. grandis state in KwaZulu Natal, South Africa compared to remote sensing models. Such modelling effort ... Read more
An intercomparison of satellite-based daily evapotranspiration estimates under different eco-climatic regions in South Africa

Author: Majozi, Nobuhle P ; Mannaerts, CM ; Ramoelo, Abel ; Mathieu, Renaud SA ; Mudau, Azwitamisi E ; Verhoef, W Date: Mar 2017 Knowledge of evapotranspiration (ET) is essential for enhancing our understanding of the hydrological cycle, as well as for managing water resources, particularly in semi-arid regions. Remote sensing offers a comprehensive means of monitoring ... Read more
An investigation into robust spectral indices for leaf chlorophyll estimation

Author: Main, Russell S ; Cho, Moses A ; Mathieu, Renaud SA ; O'Kennedy, Maretha M ; Ramoelo, Abel ; Koch, S Date: Nov 2011 Quantifying photosynthetic activity at the regional scale can provide important information to resource managers, planners and global ecosystem modelling efforts. With increasing availability of both hyperspectral and narrow band multispectral ... Read more
Mapping big tree presence in open savanna, using tree shadow and high resolution multispectral imagery

Author: Main, Russell S ; Cho, Moses A ; Mathieu, Renaud SA ; Asner, G Date: Oct 2012 Large scattered trees play an important role in the functioning of savanna landscapes. They act as focal points for various organism activities, which influence the distribution of nutrients and water within the landscape, which in turn ... Read more
Modelling nutrient concentration to determine the environmental factors influencing grass quality

Author: Dudeni-Tlhone, N ; Ramoelo, Abel ; Cho, Moses A ; Debba, Pravesh ; Mathieu, Renaud SA Date: Oct 2010 This paper uses the spatial and the least squares (Analysis of Covariance-ANCOVA) regression methods to evaluate the important environmental factors in estimating quality grass for grazing (based on the nitrogen (N) content in grass). The ... Read more
Monitoring grass nutrients and biomass as indicators of rangeland quality and quantity using random forest modelling and WorldView-2 data

Author: Ramoelo, Abel ; Cho, Moses A ; Mathieu, Renaud SA ; Madonsela, S ; van de Kerchove, R ; Kaszta, Z ; Wolff, E Date: Dec 2015 Land use and climate change could have huge impacts on food security and the health of various ecosystems. Leaf nitrogen (N) and above-ground biomass are some of the key factors limiting agricultural production and ecosystem functioning. Leaf ... Read more
Multi-phenology WorldView-2 imagery improves remote sensing of savannah tree species

Author: Madonsela, Sabelo ; Cho, Moses A ; Mathieu, Renaud SA ; Mutanga, O ; Ramoelo, Abel ; Kaszta, Z ; Van De Kerchove, R ; Wolff, E Date: Jun 2017 Biodiversity mapping in African savannah is important for monitoring changes and ensuring sustainable use of ecosystem resources. Biodiversity mapping can benefit from multi-spectral instruments such as WorldView-2 with very high spatial ... Read more
Multiple endmember spectral-angle-mapper (SAM) analysis improves discrimination of Savanna tree species

Author: Cho, Moses A ; Mathieu, Renaud SA ; Debba, Pravesh Date: Aug 2009 Differences in within-species phenology and structure driven by factors including topography, edaphic properties, and climatic variables across the landscape present important challenges to species differentiation with remote sensing. The ... Read more
Non-linear partial least square regression increases the estimation accuracy of grass nitrogen and phosphorus using in situ hyperspectral and environmental data

Author: Ramoelo, Abel ; Skidmore, AK ; Cho, Moses A ; Mathieu, Renaud SA ; Heitkönig, IMA ; Dudeni-Tlhone, N ; Schlerf, M ; Prins, HHT Date: Jun 2013 Grass nitrogen (N) and phosphorus (P) concentrations are direct indicators of rangeland quality and provide imperative information for sound management of wildlife and livestock. It is challenging to estimate grass N and P concentrations using ... Read more
On using discrete return LIDAR distributions as a proxy for waveform LIDAR signals when modeling vegetation structure

Author: Van Aardt, JAN ; Wu, J ; McGlinchy, J ; Wessels, Konrad J ; Mathieu, Renaud SA ; Kennedy Bowdoin, T ; Knapp, DE ; Asner, GP Date: Jul 2012 The goals of the study were to (i) determine if there is a direct relationship between waveform LiDAR intensity-by-height and discrete return frequency-by-height (do the distributions match?) and (ii) assess the impact of scale (does this ... Read more
Optimal individual supervised hyperspectral band selection distinguishing savannah trees at leaf level

Author: Debba, Pravesh ; Cho, Moses A ; Mathieu, Renaud SA Date: Aug 2009 This paper uses simulated annealing and focus on the spectral angle mapper (SAM), to demonstrate how the separability of two mean spectra from different species can be increased by choosing the bands that maximize the metric. It is known that ... Read more
Optimizing tree-species classification in hyperspectal images

Author: Barnard, E ; Cho, Moses A ; Debba, Pravesh ; Mathieu, Renaud SA ; Wessels, Konrad J ; van Heerden, C ; Van der Walt, Christiaan M ; Asner, GP Date: Nov 2010 The authors investigate the classification of eight prominent savanna tree species, based on hyperspectral reflectance data. Although two principal components account for 95% of the variance of the data, up to 20 components are found to be ... Read more
The potential of Sentinel-2 spectral configuration to assess rangeland quality

Author: Ramoelo, Abel ; Cho, Moses A ; Mathieu, Renaud SA ; Skidmore, AK Date: Aug 2015 Sentinel-2 is intended to improve vegetation assessment at local to global scales. Today, estimation of leaf nitrogen (N) as an indicator of rangeland quality is possible using hyperspectral systems. However, few studies based on commercial ... Read more
Regional estimation of savanna grass nitrogen using the red-edge band of the RapidEye sensor

Author: Ramoelo, Abel ; Skidmore, AK ; Cho, Moses A ; Schlerf, M ; Mathieu, Renaud SA ; Heitkönig, IMA Date: Oct 2012 The regional mapping of grass nutrients is of interest in the sustainable planning and management of livestock and wildlife grazing. The objective of this study was to estimate and map foliar and canopy nitrogen (N) at a regional scale using ... Read more

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