Method and apparatus for locating an object using reduced number of GPS satellite signals or with improved accuracy
First Claim
1. A method for identifying a location of an object to be tracked comprising the steps of:
- measuring at said object to be tracked data related to propagation time differences between signals transmitted from a plurality of satellites and received at said object to be tracked;
transmitting said data by said object to be tracked to a central station; and
calculating at said central station the location of said object to be tracked based upon the transmitted data, a predetermined database containing information constraining the location of the object to be tracked, and data derived from at least one receiver apart from said object to be tracked receiving said signals from said plurality of satellites.
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Accused Products
Abstract
The number of simultaneous equations needed to find the location solution of an asset being tracked, such as a railcar, or, in the alternative, to improve the localization accuracy of any of several positioning methods used to track assets, is reduced by using a railway track database. Known railway track locations are used to constrain the railcar (i.e., asset) location solutions. This constraint makes the Cartesian coordinate location x, y and z values interdependent and reduces the number of simultaneous equations needed to find the location solution. Since all relevant railcars must be supported on railway tracks, and railway track locations and elevations throughout North America are available in a database, the number of satellite signals required is reduced. The railway track database represents a complex set of railway tracks. Instead of forming the complete set of function factors that make up the railway track data base every time a railcar location solution is needed, a start is made from a previous solution and only those railway tracks and/or branches that are feasible (i.e., nearby) are tried. Thus, the complexity of forming all railway track function terms is reduced to forming only those needed in a short railway track "tree search".
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Citations
27 Claims
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1. A method for identifying a location of an object to be tracked comprising the steps of:
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measuring at said object to be tracked data related to propagation time differences between signals transmitted from a plurality of satellites and received at said object to be tracked; transmitting said data by said object to be tracked to a central station; and calculating at said central station the location of said object to be tracked based upon the transmitted data, a predetermined database containing information constraining the location of the object to be tracked, and data derived from at least one receiver apart from said object to be tracked receiving said signals from said plurality of satellites. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A system for identifying location of an object to be tracked comprising:
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first means situated at the object to be tracked for measuring data related to propagation time differences between signals transmitted from a plurality of satellites and for receiving each of said signals identifying an associated satellite; a central station; second means situated at the object to be tracked for transmitting said data related to propagation time differences along with associated satellite identification data to a central station; at least one GPS receiver situated apart from the tracked object for receiving said signals from said plurality of satellites; a database at said central station containing information constraining the location of the object to be tracked; and means at said central station for calculating the location of said object to be tracked based upon the transmitted data, the information in said database, and data derived from said at least one GPS receiver. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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Specification