Flexible signal source location apparatus and method therefor
First Claim
1. In a satellite communication system that includes an earth terminal and satellites, a method of providing an estimate of a location of a subscriber unit that is emitting a signal comprising the steps of:
- collecting, by at least one of said satellites, two measurements of said signal, each of said measurements having a measurement error associated therewith;
sending said measurements to said earth terminal;
generating a surface contour for each of said measurements;
finding intersection points and near intersection points between said surface contours and a surface contour representing earth'"'"'s surface;
using said intersection points and near intersection points to seed a least-squares algorithm to generate final locations;
generating statistical confidence regions around each final location using said measurement error, each confidence region having a probability associated therewith indicating the probability that said subscriber unit is within the associated confidence region, each confidence region corresponding with a geographic region on earth'"'"'s surface; and
when smaller confidence regions are desired, collecting additional measurements of said signal and repeating the steps of sending, finding, using and generating to increase said probability associated with each confidence region.
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Accused Products
Abstract
A subscriber unit (26) communicates with a satellite (12) using electromagnetic signals so that observations (102) of the signals are obtained. Surface contours are generated (104) based on the signal component measured. The surface contour intersections produce candidate locations on the earth'"'"'s surface. The candidate locations seed a least-squares estimation to produce final locations. Data produced during the least-squares fit is used to generate confidence ellipses (116) about the final locations. Most likely actual locations are determined from the fit associated with the confidence regions. A variety of signal source measurements can be used while providing a best estimate of a signal source location when an exact solution is not mathematically possible. The location is converted to coordinates that can be used in a satellite communication system (10) for making decisions regarding the granting or denying of communication services, billing rate and the like.
108 Citations
17 Claims
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1. In a satellite communication system that includes an earth terminal and satellites, a method of providing an estimate of a location of a subscriber unit that is emitting a signal comprising the steps of:
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collecting, by at least one of said satellites, two measurements of said signal, each of said measurements having a measurement error associated therewith; sending said measurements to said earth terminal; generating a surface contour for each of said measurements;
finding intersection points and near intersection points between said surface contours and a surface contour representing earth'"'"'s surface;using said intersection points and near intersection points to seed a least-squares algorithm to generate final locations; generating statistical confidence regions around each final location using said measurement error, each confidence region having a probability associated therewith indicating the probability that said subscriber unit is within the associated confidence region, each confidence region corresponding with a geographic region on earth'"'"'s surface; and when smaller confidence regions are desired, collecting additional measurements of said signal and repeating the steps of sending, finding, using and generating to increase said probability associated with each confidence region. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of providing an initial estimate of a location of a subscriber unit that is emitting a signal comprising the steps of:
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receiving at least two measurements of said signal, each of said measurements having a measurement error associated therewith; generating a surface contour for each measurement; finding intersection points and near intersection points between said surface contours and a surface contour representing earth'"'"'s surface; using said intersection points and near intersection points to seed a least-squares algorithm to generate final locations; generating statistical confidence regions around each final location using said measurement error, each confidence region having a probability associated therewith indicating the probability that said subscriber unit is within the associated confidence region, each confidence region corresponding with a geographic region on earth'"'"'s surface; and when smaller confidence regions are desired, collecting additional measurements of said signal and repeating the steps of sending, finding, using and generating to increase said probability associated with each confidence region. - View Dependent Claims (12, 13)
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14. An apparatus for determining a location of a signal source comprising:
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an earth terminal receiver for receiving measurements collected by a satellite, said measurements being from said signal source on or near earth'"'"'s surface, said satellite being part of a satellite based communication system; and a processor for; generating a surface contour for each of said measurements; finding intersection points and near intersection points between said surface contours and a surface contour representing earth'"'"'s surface; using said intersection points and near intersection points to seed a least-squares algorithm to generate final locations; generating statistical confidence regions around each final location using a measurement error associated with each of said measurement, each confidence region having a probability associated therewith indicating the probability that said signal source is within the associated confidence region, each confidence region corresponding with a geographic region on earth'"'"'s surface; and when smaller confidence regions are desired, collecting additional measurements of said signal source and repeating the steps of sending, finding, using and generating to increase said probability associated with each confidence region. - View Dependent Claims (15, 16, 17)
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Specification