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Double sampling was used to provide a cost efficient estimate of the accuracy of a Landsat Thematic Mapper (TM) classification map of a scene located in the Rocky Mountain National Park, Colorado. In the first phase, 200 sample points were randomly selected to assess the accuracy between Landsat TM data and aerial photography. The overall accuracy and Kappa statistic were 49.5 per cent and 32.5 per cent, respectively. In the second phase, 25 sample points identified in the first phase were selected using stratified random sampling and located in the field. This information was used to correct for misclassification errors associated with the first phase samples. The overall accuracy and Kappa statistic increased...
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This paper discusses several difficulties encountered in detecting and monitoring temporal changes in vegetation using multispectral imagery from airborne or spaceborne sensors. These difficulties are due to (1) temporal change in the vegetation state; (2) temporal change in the soil/rock signature; and (3) difficulty in discriminating vegetation from soil or rock background. The seasonal dynamics of soil and vegetation was investigated over two years on permanent sample plots in a natural fenced-off area in the semi-arid region (200 mm annual average rainfall) of the Northern Negev, Israel. Results show that temporal analysis of natural vegetation in semi-arid regions should take into account three ground features--perennials,...
Bromus tectorum (cheatgrass) is an annual Eurasian grass that has invaded rangelands of the western USA. Being both a fire follower and a fire promoter, it can rapidly exclude native vegetation and is among the greatest threats to conservation in the region. Key to land management is a strong understanding of B. tectorum distribution and density. Percentage ground cover of B. tectorum was estimated and mapped as a continuous variable over 13.3millionha in Nevada, USA. Estimation involved a statistical model derived from 262 training plots, two dates of six scenes from Landsat 7 ETM+ imagery collected in 2001, and elevation. Absence of B. tectorum in many plots led to a dataset that was left-censored at zero for...
    map background search result map search result map Temporal dynamics of soil and vegetation spectral responses in a semi-arid environment Temporal dynamics of soil and vegetation spectral responses in a semi-arid environment