| 摘要 |
A system, a signal bearing medium embodying a program of machine-readable instructions, and a method employing Global Positioning System (GPS) satellites to determine the current pace, the distance traveled and speed of a person, for example a runner, are disclosed. A GPS receiver for receiving signals from GPS satellites is attached to the person. A processor processes the signals received at a plurality of points from sub-sets of GPS satellites to determine the Earth Centered Earth Fixed (ECEF) fix in the x, y, and z planes relative to the center of the earth of each point. The processor detects when the signals are received from a different sub-set of satellites and corrects for the resulting fix error. The processor calculates the relative distance of the segment between the ECEF fixes of each pair of sequentially adjacent points, and adds together the distances of the segments to determine the distance of the path traveled by the person, which is defined by the points. Errors associated with determining position relative to navigational references such as latitude and longitude are not incurred because relative ECEF fixes are used to determine the distance rather than latitude and longitude fixes. Also, "Selective Availability" error, which is an error introduced into GPS signals by the U.S. military that limits the accuracy of GPS fixes relative to navigational references, does not degrade the accuracy of the distance calculations because the relative distance between the points is used to determine the distance traveled, rather than the distance of the points from navigational references. The processor calculates the elapsed time between selective points, and determines the average speed or pace of the person between selective points and current speed in minutes/mile. A storage device stores data structures representing the ECEF fixes of selective points, and data structures representing relative times that GPS signals are received at selective points. A signal-bearing medium tangibly embodying a program of for performing the above method that are executable by a digital processing device. |
