Navigational plotting system

• US 4,393,448 A
• Filed: 02/15/1980
• Issued: 07/12/1983
• Est. Priority Date: 02/15/1980
• Status: Expired due to Term

• Current Assignee: Epsco, Inc.
• Original Assignee: Epsco, Inc.
• Inventors: Dunn, Thomas J., Szakacs, Gabor L., Yuniskis, Donald G. Jr., Nguyen, Nghia V.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US06/121,651
• Time in Patent Office: 1,243 Days
• Field of Search: 364/443, 364/444, 364/449, 364/450, 364/520, 364/452, 340/24, 340/27 NA, 343/112 C, 343/112 PT, 235/92 MP, 73/178 R, 33/1 M
• US Class Current: 701/207
• CPC Class Codes: G01C 21/22 Plotting boards

Abstract

An improved navigational plotting system having convenient initialization and the ability to compute and superimpose hyperbolic time difference lines on a chart includes an X-Y plotter for plotting the position and course of a vessel on a navigational chart or a plain piece of paper, dictated by the reception of hyperbolic navigation signals. Ambiguity-free conversion to latitude and longitude is done automatically without the necessity of manually entering the initial latitude and longitude of the vessel. Remote initialization is established by placing the pen of the plotter on a known point or position on the chart and entering the latitude and longitude of this known position or its hyperbolic navigation coordinates, with all subsequent plot locations being referenced to this point on the chart. A set of default pre-stored conditions are utilized in the initialization procedure in which preset scale size and hyperbolic line parameters are assumed, with convenient override sequences being provided. The plotter includes a high accuracy rapid hyperbolic line drawing system utilizing a specialized approximation sequence for those charts which are not provided with hyperbolic navigation TD lines. A base line extension zone where hyperbolic position ambiguity is difficult to resolve (danger zone) is indicated by the preventing of the drawing of hyperbolic lines in this zone, thereby to give the navigator adequate indication that hyperbolic navigation readings may be ambiguous. A system is provided for rapid counter setting for the counters which drive the pen and also indicate vessel location or destination. This system utilizes differing rates of clocking the counters depending on whether the vessel or destination is on-chart or off-chart. As a further feature, velocity filtering prevents wild pen movement as a result of system transients. Additional auxiliary readout functions such as destination, range, velocity, time of arrival, heading, etc. are also provided.

Claims

1. A plotter for use on board a vehicle in which said plotter is provided with navigation signals received at said vehicle comprising:

an X/Y plotter having a moveable pen and a charting surface;

means for driving said pen in accordance with the difference in position between the position represented by said navigation signals and the position of an initialization point on the charting surface; and

,

means for establishing said initialization point at a position on the charting surface remote from that representing the position of said vehicle, said establishing means including said pen placed at the position on said charting surface representing said remote initialization point position and means for automatically providing said driving means with the navigation signal coordinates of said pen when at said remote initialization point position.

2. A plotting system for use on board a vehicle in which said plotter is provided with navigation signals from a receiver at said vehicle comprising:

means for generating pen positioning signals in accordance with navigation signals from said receiver, said pen positioning signals being in the form of drive pulses;

an X/Y plotter having a moveable pen, a charting surface and stepping motor means coupled to said drive pulses for positioning said pen;

at least one counter coupled to said drive pulses for keeping track of the effective position of said pen by virtue of the count thereof; and

,

means for facilitating rapid off-chart calculations of pen position including means for increasing the rate of said drive pulses to said counter when the position dictated by said pen positioning signals indicates a pen move within the off-chart area.

3. The plotting system of claim 2 wherein said rate increasing means increases said drive pulse rate when the effective position of said pen is either in an off-chart position and said effective position is to be moved towards said chart, or when the effective position of said pen is either at a chart edge and is to be moved off-chart, or the effective position of said pen is off-chart and is to be moved further off-chart.

4. The plotting system of claim 2 wherein said pen positioning signals correspond in number to the difference in position between one position and another position.

5. The plotting system of claim 2 wherein said pen positioning signals are generated in response to the receipt of said navigation signals and corresponds in number to the difference in position between a present vehicle position and a prior vehicle position.

6. The plotting system of claim 2 wherein said pen positioning signals are generated in response to a predetermined set of navigation signals and an initial set of navigation signals.

7. The plotting system of claim 2 and further including means for interrupting the coupling of said drive pulses to said stepping motor means when the effective position of said pen is off-chart.

8. The plotting system of claim 7 wherein said interrupting means includes an off-chart counter and means for coupling said drive pulses to said off-chart counter when said pen reaches a predetermined edge of said charting surface such that when said pen reaches an edge of said charting surface, said pen stops and the drive pulses are diverted to said off-chart counter, a predetermined count of said off-chart counter controlling said coupling means to remove said drive pulses from said off-chart counter and to apply said drive pulses to said stepping motor means.

9. The plotting system of claim 8 wherein said off-chart counter is driven at said increased rate.

10. The plotting system of claim 8 wherein said off-chart counter is an up-down counter, said predetermined count is zero, and further including means for determining the direction of said pen relative to said edge and for controlling the direction of said counter depending on whether the movement of the effective position of said pen is towards or away from said predetermined edge.

11. The plotting system of claim 10 wherein said direction determining means includes switch means for sensing when said pen is at said predetermined edge.

12. A plotting system for use on board a vehicle in which said plotter is provided with navigation signals from a receiver at said vehicle comprising:

means for generating pen positioning signals in accordance with navigation signals from said receiver, said pen positioning signals being in the form of drive pulses;

an X/Y plotter having a moveable pen, a charting surface and stepping motor means coupled to said drive pulses for positioning said pen;

at least one counter coupled to said drive pulses for keeping track of the effective position of said pen by virtue of the count thereof;

means for increasing the rate of said drive pulses to said counter when the position dictated by said pen positioning signals indicate a pen move within the off-chart area; and

,

means for interrupting the coupling of said drive pulses to said stepping motor means when the effective position of said pen is off-chart, said interrupting means including an off-chart counter, means for coupling said drive pulses to said off-chart counter when said pen reaches a predetermined edge of said charting surface such that when said pen reaches an edge of said charting surface, said pen stops and the drive pulses are diverted to said off-chart counter, and means responsive to a predetermined count of said off-chart counter for controlling said coupling means to remove said drive pulses from said off-chart counter and to apply said drive pulses to said stepping motor means.

13. The plotting system of claim 12 wherein said off-chart counter is driven at said increased rate.

14. The plotting system of claim 12 wherein said off-chart counter is an up-down counter, said predetermined count is zero, and further including means for determining the direction of said pen relative to said edge and for controlling the direction of said counter depending on whether the movement of the effective position of said pen is towards or away from said predetermined edge.

15. The plotting system of claim 14 wherein said direction determining means includes switch means for sensing when said pen is at said predetermined edge.

16. A plotter for use on board a vehicle in which said plotter is provided with navigation signals received at said vehicle comprising:

an X/Y plotter having a moveable pen and a charting surface having fixed objects thereon;

means for driving said pen in accordance with the difference in position between the position represented by said navigation signals and the position of an initialization point on the charting surface; and

,

means for establishing said initialization point at a position on the charting surface remote from that representing the position of said vehicle, said establishing means including said pen placed at a fixed object on said charting surface representing said remote initialization point position and means for automatically providing said driving means with the navigation signal coordinates of said pen when at said remote initialization point position.