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Navigation equipment which determines current position dependent on difference between calculated value of self-contained navigation and measured value of radio navigation

  • US 5,422,639 A
  • Filed: 09/16/1993
  • Issued: 06/06/1995
  • Est. Priority Date: 09/16/1992
  • Status: Expired due to Term
First Claim
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1. A navigation equipment which is installed on a mobile object in order to produce a current position of the mobile object as an output, comprising:

  • radio navigation means for measuring the current position of said mobile object on the basis of electric waves received from artificial satellites;

    azimuth measurement means for measuring a traveling azimuth of said mobile object on the basis of at least one of an angular velocity and a geomagnetic angle;

    distance measurement means for measuring a driven distance of said mobile object;

    memory means for storing road map information therein;

    self-contained navigation means for estimating one of said current position of said mobile object and a drive history thereof up to a current time by use of the traveling azimuth measured by said azimuth measurement means and the driven distance measured by said distance measurement means up to the current time since a given drive starting position, and then collating one of the estimated current position or the estimated drive history with the road map information read out of said memory means, thereby determining a current position of said mobile object; and

    position correction means for delivering the determined current position of said self-contained navigation means as the final current position in a case where said determined current position of said self-contained navigation means and the measured current position of said radio navigation means do not differ in excess of a predetermined distance, and for delivering said measured current position of said radio navigation means as the final current position and also giving said self-contained navigation means said measured current position of said radio navigation means as a new drive starting point in a case where the determined and measured current positions differ in excess of the predetermined distance, said position correction means collates said determined current position of said self-contained navigation means with said road map information, thereby deciding if said determined current position lies either on or in the vicinity of a road; and

    upon deciding that said determined current position lies either on or in the vicinity of the road, said position correction means delivers said determined current position of said self-contained navigation means as said final current position and does not give said self-contained navigation means said measured current position of said radio navigation means as the new drive starting point even in the case where said determined and measured current positions differ in excess of said predetermined distance.

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