| 摘要 |
Method and apparatus for indicating and allowing a traveler to follow a chosen route from an origin point to a destination point on the Earth's surface, using a portable Satellite Positioning System and audible or visual information presentation means. Initially, the traveler positions a map or chart with the intended route thereon on a light-sensitive table and traces each segment of the route with a pressure-sensitive light pen. Information on each segment and the locations of its endpoints is entered in a microprocessor. Coded information shown on the map itself is entered into the microprocessor, using a bar code reader or similar device. Along the route, the traveler carries the microprocessor and a portable Satellite Positioning System (SPS) antenna and receiver/processor, connected to the microprocessor. As the traveler approaches each turn point or decision point in the route, determined by a common endpoint of two consecutive segments, the apparatus advises the traveler audibly or visually that the decision point is near and of the initial direction of the next consecutive segment. The traveler is also advised if the actual route deviates significantly from the chosen route and of the appropriate corrective action to be taken to reduce the deviation. Optionally, the apparatus can include information on one or more alternative routes that can be used if a portion of the chosen route is impassible or otherwise unavailable. This approach is of special usefulness to a visually impaired or visually preoccupied traveler. The SPS may incorporate differential positioning to improve the accuracy of the SPS-determined location.
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