Robert S. Conker

A dual plane variation of the Hough transform for detecting non-concentric circles of different radii

Abstract The Hough transform for circle detection requires the search of a 3-dimensional parameter space for circles of arbitrary radius. A technique has been developed which calculates intersection points of edge gradient vectors storing response weights in one plane and the product of weights and radii in another plane effectively eliminating the radius dimension of the parameter space. The result is a significant savings in both search time and storage in the parameter space accumulator.

An introduction to Wide Area Augmentation System and its predicted performance

The Federal Aviation Administration is developing a Wide Area Augmentation System (WAAS) to GPS that will broadcast clock, ephemeris, and ionospheric corrections. Aviation user equipment will apply the corrections to GPS measurements and also convert error bounds into the position domain. Flight operations can be conducted using WAAS guidance only when the horizontal, and in some cases also the vertical, position error bound is less than a threshold that depends on the phase of flight. The expected fraction of time that a given flight operation can be conducted is termed its availability. Geomagnetic storms sometimes are accompanied by large spatial and temporal gradients in ionospheric delay that result in an increase in ionospheric and position error bounds, which reduces availability. The paper estimates availability of precision approach operations under various scenarios.