Jan van Aardt

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a Council for Scientific and Industrial Research (CSIR), Natural Resources and Environment (NRE), Earth Observation Group, P.O. Box 395, Pretoria 0001, South Africa b Department of Global Ecology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA 94305, USA c RIT: Center for Imaging Science, Digital Imaging and Remote Sensing Group, 54 Lomb(More)
Although a variety of hierarchical image segmentation procedures for remote sensing imagery have been published, none of them specifically integrates remote sensing time series in spatial or hierarchical segmentation concepts. However, this integration is important for the analysis of ecosystems which are hierarchical in nature, with different ecological(More)
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 remote sensing. The objectives of this paper are as follows: 1) to evaluate the classification performance of a(More)
The use of hyperspectral approaches for early detection of plant stress caused by Venturia inaequalis (apple scab) was investigated to move towards more efficient and reduced application of pesticides, fertilizers or other crop management treatments in apple orchards. Apple leaves of the resistant cultivar,Rewena and the susceptible cultivar,Braeburn, were(More)
A raw incoming (received) Light Detection And Ranging (LiDAR) waveform typically exhibits a stretched and relatively featureless character, e.g., the LiDAR signal is smeared and the effective spatial resolution decreases. This is attributed to a fixed time span allocated for detection, the sensor’s variable outgoing pulse signal, receiver impulse response,(More)
Remote sensing is viewed as a cost-effective alternative to intensive field surveys in assessing site factors that affect growth of Eucalyptus grandis over broad areas. The objective of this study was to assess the utility of hyperspectral remote sensing to discriminate between site qualities in E. grandis plantation in KwaZulu-Natal, South Africa. The(More)
The objectives of this research were to investigate (1) the influence of a geometric laser measurement pattern and (2) the shadow effect on the accuracy of a quantitative mathematical description of individual tree structure using a terrestrial laser system. The commercially available SICK Laser-Measurement-System-200 (LMS200, Sick, A.G.) was used in this(More)
This paper evaluated the capacity of SPOT VEGETATION time-series to monitor herbaceous fuel moisture content (FMC) in order to improve fire risk assessment in the savanna ecosystem of Kruger National Park in South Africa. In situ herbaceous FMC data were used to assess the Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index(More)
The repeated occurrence of severe wildfires has highlighted the need for development of effective vegetation monitoring tools. We compared the performance of indices derived from satellite and climate data as a first step toward an operational tool for fire risk assessment in savanna ecosystems. Field collected fire activity data were used to evaluate the(More)
With the development of increasingly advanced airborne sensing systems, there is a growing need to support sensor system design, modeling, and product-algorithm development with explicit 3D structural ground truth commensurate to the scale of acquisition. Terrestrial laser scanning is one such technique which could provide this structural information.(More)