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Richard A. Champion

Publications and source records attributed to Richard A. Champion.

4 recordsLinked to original sources
USGS2008

A Bernoulli Formulation of the Land-Use Portfolio Model

Decision making for natural-hazards mitigation can be sketched as knowledge available in advance (a priori), knowledge available later (a posteriori), and how consequences of the mitigation decision might be viewed once future outcomes are known. Two outcomes - mitigating for a hazard event that will occur, and not mitigating for a hazard event that will not occur - can be considered narrowly correct. Two alternative outcomes - mitigating for a hazard event that will not occur, and not mitigating for a hazard event that will occur - can be considered narrowly incorrect. The dilemma facing the decision maker is that mitigation choices must be made before the event, and often must be made with imperfect statistical techniques and imperfect data.

Open-File Report↗
USGS2007

Cost-Benefit Analysis of Computer Resources for Machine Learning

Machine learning describes pattern-recognition algorithms - in this case, probabilistic neural networks (PNNs). These can be computationally intensive, in part because of the nonlinear optimizer, a numerical process that calibrates the PNN by minimizing a sum of squared errors. This report suggests efficiencies that are expressed as cost and benefit. The cost is computer time needed to calibrate the PNN, and the benefit is goodness-of-fit, how well the PNN learns the pattern in the data. There may be a point of diminishing returns where a further expenditure of computer resources does not produce additional benefits. Sampling is suggested as a cost-reduction strategy. One consideration is how many points to select for calibration and another is the geometric distribution of the points. The data points may be nonuniformly distributed across space, so that sampling at some locations provides additional benefit while sampling at other locations does not. A stratified sampling strategy can be designed to select more points in regions where they reduce the calibration error and fewer points in regions where they do not. Goodness-of-fit tests ensure that the sampling does not introduce bias. This approach is illustrated by statistical experiments for computing correlations between measures of roadless area and population density for the San Francisco Bay Area. The alternative to training efficiencies is to rely on high-performance computer systems. These may require specialized programming and algorithms that are optimized for parallel performance.

Open-File Report↗
USGS1989

Image processing techniques for digital orthophotoquad production

Orthophotographs have long been recognized for their value as supplements or alternatives to standard maps. Recent trends towards digital cartography have resulted in efforts by the US Geological Survey to develop a digital orthophotoquad production system. Digital image files were created by scanning color infrared photographs on a microdensitometer. Rectification techniques were applied to remove tile and relief displacement, thereby creating digital orthophotos. Image mosaicking software was then used to join the rectified images, producing digital orthophotos in quadrangle format.

Photogrammetric Engineering and Remote Sensing↗