Tide computation apparatus and method of using the same

Claim 2

Computation apparatus for determining the date and/or time of a recurrent periodic event, comprising: a base board provided with a first scale having a plurality of index marks signifying the days of the year and a second scale having a plurality of index marks signifying the hours of the day, said first scale having a plurality of successive sections each extending along said second scale; a transparent cover plate overlying said base board and said first scale, said cover plate having indicia thereon signifying the stages of said event; and an arm mounted for movement over said cover plate and having a straight edge for facilitating the drawing of lines on said cover plate.

Claim 3

Computation apparatus as recited in claim 1, wherein said first scale is spiral and said sections are successive convolutions of said spiral and wherein said second scale is circular and surrounds said first scale.

Claim 4

Computation apparatus as recited in claim 2, wherein said event is the tide and said first scale has a number of said convolutions N governed by the equation: N (365/L) where L is the number of days in a lunar month, being equal to 29.5305884.

Claim 5

Computation apparatus as recited in claim 3, wherein N 12.36 and wherein the angle between said index marks of said first scale is 12.1907 degrees.

Claim 6

Computation apparatus as recited in claim 3, wherein the outermost index mark on said first scale signifies the date Mar. 1 and the innermost index mark on said first scale signifies the date Feb. 29.

Claim 7

Computation apparatus as recited in claim 2, wherein said cover plate is rotatable on said base board about an axis concentric with said spiral first scale and said arm is rotatable about said axis to place said straight edge along radial lines with respect to said axis.

Claim 8

Computation apparatus as recited in claim 6, wherein the upper surface of said cover plate is roughened to facilitate marking said cover plate with a pencil.

Claim 9

Computation apparatus as recited in claim 6, wherein said event is the tide and said indicia on said cover plate include a first index mark signifying high tide, a second index mark signifying low tide, a third index mark signifying high tide, and a fourth index mark signifying low tide.

Claim 10

Computation apparatus as recited in claim 8, wherein said cover plate is further provided with a fifth index mark signifying high tide, said fifth index mark being spaced clockwise from said first index mark a distance d along said second scale corresponding to the approximate 50 minute difference in time between corresponding high tides on successive days, the second index mark being spaced clockwise from said first index mark by a distance equal to six hours plus d/4, the third index mark being spaced clockwise from said first index mark by a distance equal to twelve hours plus (2d/4), and the fourth index mark being spaced clockwise from said first index mark by a distance equal to 18 hours plus (3d/4).

Claim 11

Computation apparatus as recited in claim 9, further comprising a third circular scale signifying the phases of the moon with a full moon being positioned at midnight and a new moon being positioned at midday of said second scale.

Claim 12

A method of computing the time of tides for a particular port, comprising: providing computation apparatus as recited in claim 10; looking up the moon''s phases in an astronomical daily calendar for a selected date and determining the date of the next full moon; looking up in a tide table the time of the high tide most closely following midnight for said particular port on said date of the next full moon; rotating said cover plate of said apparatus to being said first index mark in coincidence with said time for the high tide most closely following midnight on said second scale; rotating said arm to being the straight edge of said arm in coincidence with the index mark for the date of the next full moon on the first scale; marking the surface of said cover plate along said straight edge of said arm to form a ''''home port date line;'''' rotating the arm to bring the straight edge of said arm in coincidence with the index mark for midnight on said second scale; marking the surface of said cover plate along said straight edge of said arm to form a ''''moon line;'''' rotating said cover plate to bring said ''''home port date line'''' in coincidence with the index mark for a given date on said first scale; and determining from the times on said second scale coincident with said index marks on said cover plate the times of the tides for said given date corresponding to said index marks on said cover plate.

Claim 13

A method as recited in claim 11, further comprising the step of determining the phase of the moon on said given date by noting the moon phase on said third scale coincident with said ''''moon line'''' when said ''''home port date line'''' is aligned with said given date on said first scale.

Claim 14

Computation apparatus as recited in claim 2, wherein said event is the phase of the moon and said first scale has a number of said convolutions N governed by the equation: N (365/L) where L is the number of days in a lunar month, being equal to 29.5305884, and wherein said apparatus further comprises a third circular scale signifying the phases of the moon with a full moon being positioned at midnight and a new moon being positioned at midday of said second scale.