Area navigational system

Claim 2

Apparatus for air navigation to a point of known location which is separated from a VOR beacon of known location, said apparatus comprising: a storage means for storing signals representative of, respectively, the known locations of said point and said VOR, an estimated ground speed, an estimated range-to-go to said point, and an estimated course to said point; means for receiving from a VOR signal receiver/VOR bearing generator a signal representative of the current bearing of said VOR beacon from said apparatus; a bearing change generator responsive to signals generated by said VOR receiver/generator for generating a signal that is representative of the change in the VOR bearing; a course estimator responsive to signals generated by said bearing change generator and signals in said storage means for generating a signal representative of an updated course heading, said course estimator including, (a) a first provisional range-to-VOR generator responsive to signals representative of the current estimated course heading and the current VOR bearing for deriving a signal representative of a provisional range-to-VOR, (b) a second provisional range-to-VOR generator responsive to signals representative of the current estimated ground speed and the change of the VOR bearing for deriving a signal representative of a provisional range-to-VOR, (c) a range filter for comparing the relationship between said signals representative of said provisional ranges-to-VOR with a predetermined permitted relationship and selecting one of said two signals representative of provisional ranges-to-VOR on the basis of said comparison, (d) a provisional course generator responsive to the signal representative of the one of said provisional ranges-to-VOR selected on the basis of said comparison for generating a signal representative of a provisional course, and (e) a course updater responsive to said signal representative of said provisional course for generating a signal representative of an updated course; a range-to-point estimator responsive to said signal representative of said updated estimated course stored in said storage means for generating a signal representative of the range-to-point, and control means for controlling said bearing sampling and for activating said course estimator at predetermined intervals.

Claim 3

The apparatus of claim 1 wherein said predetermined intervals are between one second and two minutes.

Claim 4

The apparatus of claim 1 wherein said range filter comprises selecting means for selecting the value of said second range-to-VOR estimate whenever the value of said first estimate is inconsistent with the value of said second estimate according to a preestablished consistency test.

Claim 5

The apparatus of claim 3 wherein said range filter selection means comprises comparison means for comparing the values of the first and second provisional VOR ranges generated by said provisional VOR range generators, and selecting said second provisional value whenever the absolute value of the difference between them exceeds a predetermined distance of between one and three nautical miles.

Claim 6

The apparatus of claim 1 wherein said storage means stores signals representative of a past provisional estimated course and said course updater further comprises a course evaluation filter for comparing said signals representative of said current and said past provisional courses with a predetermined permitted relationship and updating said signal representative of said current estimated course.

Claim 7

The apparatus of claim 5 wherein said predetermined number is between 5 and 20 degrees.

Claim 8

The apparatus of claim 1 further comprising a ground speed estimator for updating said value of said ground speed using signals representative of said updated range to said point.

Claim 9

The apparatus of claim 7 wherein said ground speed estimator comprises a provisional ground speed generator which generates a signal representative of the provisional rate of change in the range to said point responsive to said signal representative of said updated range to said point, and a ground speed filter which generates a signal representative of a value for an updated ground speed responsive to said signal representative of the provisional ground speed and said stored signal representative of said estimated ground speed.

Claim 10

The apparatus of claim 1 further comprising a output means for outputing a value representative of said updated course heading to an automatic-pilot means for maintaining said aircraft on said updated course heading.

Claim 11

In a method of air navigation to a point of known location which is separated from a VOR beacon of known location, said method comprising providing data signals representative of, respectively, the known location of said known point and said VOR, an estimated ground speed, an estimated range-to-go to said point, and an estimated course to said second point, that improvement comprising: updating the value for the current estimated heading to said point repeatedly, at predetermined intervals, by (a) deriving a data signal representative of a first estimate of the range to the VOR from a data signal representative of the current estimated heading to said point and a data signal representative of the current bearing to the VOR, and (b) sampling signals representative of the current bearing of the VOR beacon, and, after sampling, generating a data signal representative of the current bearing to the VOR beacon and a data signal representative of the rate of change of that bearing, (c) filtering said data signal representative of said first estimate of the VOR range by deriving a data signal representative of a second estimate of the VOR range and comparing said data signal representative of said first estimate to said data signal representative of the value of said second estimate, said data signal representative of the value of said second estimate being derived from said stored data signal representative of the current estimated ground speed and said data signal representative of the change of the bearing to VOR, and (d) deriving a data signal representing the value of a provisional course heading to the point from the data signal representative of said filtered range to the VOR; generating a data signal representative of a reevaluated course heading using said data signal representative of said selected provisional heading; and generating a data signal representative of the value of an updated range-to-go to said second waypoint using the a data signal representative of said updated course heading.

Claim 12

In a method of air navigation to a point of known location which is separated from a VOR beacon of known location, said method comprising providing data signals representative of, respectively, the known location of said known point and said VOR, an estimated ground speed, an estimated range-to-go to said point, and an estimated course to said second point, that improvement comprising: updating the value for the current estimated heading to said point repeatedly, at predetermined intervals, by (a) deriving a data signal representative of a first estimate of the range to the VOR from a data signal representative of the current estimated heading to said point and a data signal representative of the current bearing to the VOR, and (b) sampling signals representative of the current bearing of the VOR beacon, and, after sampling, generating a data signal representative of the current bearing to the VOR beacon and a data signal representative of the rate of change of that bearing, (c) filtering said data signal representative of said first estimate of the VOR range by deriving a data signal representative of a second estimate of the VOR range and comparing said data signal representative of said first estimate to said data signal representative of the value of said second estimate, said data signal representative of the value of said second estimate being derived from said stored data signal representative of the current estimated ground speed and said data signal representative of the change of the bearing to VOR, and (d) deriving a data signal representing the value of a provisional course heading to the point from the data signal representative of said filtered range to the VOR; generating a data signal representative of a reevaluated course heading using said data signal representative of said selected provisional heading; and generating a data signal representative of the value of an updated range-to-go to said second waypoint using the a data signal representative of said updated course heading.

Claim 13

The method of claim 10 wherein said predetermined intervals are between one second and two minutes.

Claim 14

The method of claim 10 wherein said filtering step comprises selecting said data signal representative of said second VOR range estimate whenever the data signal representing said first estimate is inconsistent with the data signal representing said second estimate according to a preestablished consistency test.

Claim 15

The method of claim 12 wherein said consistency test comprises comparing the absolute value of the difference of said data signals representative of said first and second estimates to a predetermined data signal representative of a distance of between one and three nautical miles.

Claim 16

The method of claim 10 wherein a data signal representative of said provisional heading is used to replace said stored data signal representative of the current estimated heading only if the difference between the data signal representative of the current provisional heading and the stored data signal representative of the most recent previous provisional heading is less than a data signal representative of a predetermined number of degrees.

Claim 17

The method of claim 14 wherein said predetermined number is between 5 and 20 degrees.

Claim 18

The method of claim 10 wherein a data signal representative of said updated range to said point is used to reevaluate the data signal representative of said current estimated ground speed.

Claim 19

The method of claim 16 wherein said reevaluation of said estimated ground speed comprises deriving a data signal representative a provisional rate of change in the range-to-go to said known point using data signals representative of the current range-to-go and the most recent previous range-to-go, and filtering a data signal representative of said current estimated ground speed using said provisional rate of change in the range-to-go to said waypoint.

Claim 20

The method of claim 10 further comprising outputing a data signal representative of said updated course heading to an automatic pilot means for maintaining said aircraft on said course heading.

Claim 21

Apparatus for air navigation to a point which is separated from a VOR beacon by a known amount, said apparatus comprising: a storage means for storing signals representative of, respectively, the coordinate locations of said point and said VOR, an estimated ground speed, an estimated range-to-go to said point, and an estimated course to said point; a receiving means for receiving from a VOR signal receiver/VOR bearing generator a signal representative of the current bearing of said VOR beacon from said apparatus; a bearing change generator responsive to signals generated by said VOR receiver/generator for generating a signal that is representative of the change in the VOR bearing; a coordinates estimator responsive to signals generated by said bearing change generator and signals in said storage means for generating signals representative of coordinates of said point with respect to present location of said apparatus said coordinates estimator including, (a) a first provisional range-to-VOR generator responsive to signals representative of the current estimated course heading and the current VOR bearing for deriving a signal representative of a provisional range-to-VOR, (b) a second provisional range-to-VOR generator responsive to signals representative the current estimated ground speed and the change of the VOR bearing for deriving a signal representative of a provisional range-to-VOR, (c) a range filter for comparing the relationship between said signals representative of said provisional ranges-to-VOR with a predetermined permitted relationship and selecting one of said two signals representative of provisional ranges-to-VOR on the basis of said comparison, (d) a provisional first coordinate generator responsive to said signal representative of said selected range-to-VOR for generating a signal representative of a provisional estimate of one of said coordinates of said point with respect to said apparatus, (e) a first coordinate updater responsive to said signal representative of said provisional first coordinate estimate for generating a signal representative of an updated first coordinate, (f) a second coordinate estimator responsive to said signal representative of said updated first coordinate for generating a signal representative of the other of said range and course coordinates; and control means for controlling said bearing sampling and for activating said range and course coordinates estimator at predetermined intervals.

Claim 22

Apparatus for air navigation to a point which is separated from a VOR beacon by a known amount, said apparatus comprising: a storage means for storing signals representative of, respectively, the coordinate locations of said point and said VOR, an estimated ground speed, an estimated range-to-go to said point, and an estimated course to said point; a receiving means for receiving from a VOR signal receiver/VOR bearing generator a signal representative of the current bearing of said VOR beacon from said apparatus; a bearing change generator responsive to signals generated by said VOR receiver/generator for generating a signal that is representative of the change in the VOR bearing; a coordinates estimator responsive to signals generated by said bearing change generator and signals in said storage means for generating signals representative of coordinates of said point with respect to present location of said apparatus said coordinates estimator including, (a) a first provisional range-to-VOR generator responsive to signals representative of the current estimated course heading and the current VOR bearing for deriving a signal representative of a provisional range-to-VOR, (b) a second provisional range-to-VOR generator responsive to signals representative the current estimated ground speed and the change of the VOR bearing for deriving a signal representative of a provisional range-to-VOR, (c) a range filter for comparing the relationship between said signals representative of said provisional ranges-to-VOR with a predetermined permitted relationship and selecting one of said two signals representative of provisional ranges-to-VOR on the basis of said comparison, (d) a provisional first coordinate generator responsive to said signal representative of said selected range-to-VOR for generating a signal representative of a provisional estimate of one of said coordinates of said point with respect to said apparatus, (e) a first coordinate updater responsive to said signal representative of said provisional first coordinate estimate for generating a signal representative of an updated first coordinate, (f) a second coordinate estimator responsive to said signal representative of said updated first coordinate for generating a signal representative of the other of said range and course coordinates; and control means for controlling said bearing sampling and for activating said range and course coordinates estimator at predetermined intervals.