Note: Descriptions are shown in the official language in which they were submitted.
CA 02273730 1999-06-08
. =
FsLECTRONIC TIDE METSR, METHOD FOR CALCLTLATING A HIGH/I.O'VV TIDE
TINffi AND RBCORDING MEDY'C.TM W].TH A PROGRAM FOR EXECUTIIVG THE
SAME MBTHOD
BACKC-ROLTND OF THE INVENTTON
Field of the invention
The present invention relates to an electronic tide meter
for calculating a high tide time and low tide tirne and display
the result, a method for calculating a high/low tide time and
a computer-readable recording medium recorded with a program
to execute the method.
Description of the Related Art
Tide, as sea surface rise and fall phenomenon, is a
phenomenon to which attention should be paid by those
paxticularly engaged in fishery. Above all, tide rise and fall
are considered important also for those who enjoy shell
S7athering or marine sports in the coastal area.
Knowing tide phenomenon, particularly a high tide time and
low tide time within a day, is achieved by calculating tide
levels based on a harmonic dissolution method. Generally, the
results of tide level calculations are opQnod to public as
regional tide information by public agencies. High tide time
and low tide time are to be known by reading the tide
information.
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However, 5uc:h rvading is inefficient tor those who always
require information of tide phenomenon. Also, in many cases
all of the opened tide phenomenon information are not always
required_ Thus, there has been a desire for a means to know
desired tide phenomenon information, particularly high tide
time and low tide time.
Under such a situation, an electronic tide meter has been
proposed which derives a tide level estimating equation from
previously stored tide data and calculates a desirably-dated
high tide time and low tide time using the derived tide level
estimating equation to display the result_ Tide level
estimating equation is a calculating equation prescribed by the
harmonic dissolving method using empirically-obtained
regional tide data, to determine a tide level at a certain time.
For example, according to an electronic tide meter disclosed
in JP-H-6-27868 publication, tide levels at a certain time
interval corresponding to one day are determined using the
above-described tide level estimating equation, and from the
determined tide data an extreme values are derived by an
apQroximation method. Then, from the derived extreme values
an extreme value with a proper t.irne .interval only is taken out.
The taken-out extreme value as a high tide or low tide level
is calculated for a high tide time and low tide txme_
Meanwhile, according to a tide display apparatus
disclosed in JP-A-58-146819 publication, a tide as determined
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from the above-described tide level eetimating equation ia
graph-displayed to enable reading a hiQh tide time and low tide
time from a displayQd graph.
However, in order to determine a high tide time and low
tide time with accuracy, it is required in the above-mentioned
tide level estimatirig equation to determine increased number
of tide levels with a time interval as short as possible. To
achieve it, th*re has been a problem that a memory with a large
capacity had to be secured to store many of calculated tide data
besides increased operation time.
zn the elcctronic tide meter disclosed in the above-
mentioned JP-B-6-27868 publication, in order to determine a
high tide time and low tide time with higher accuracy, it has
also been required to determine many of tide data from the tide
level estimating equation with a short time interval.
Meanwhile, the above-mentioned tide display appara=tus
disclosed in the JP-A-58-146819 publication is an apparatus
noticing on its display way rather than calculating a high tide
time and low tide time, and includes a similar problem to the
electronic tide meter disclosed in the JP-B-6-27+368
publication.
eLMMaRY OF THE INVENT2nrJ
The present invention has been made in view of
inconvenience possessed by the prior arts, and
an embodiment of the present invention may
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provide an electronic tide meter for calculating a high tide
time and low tide time with accuracy and at high speed, a high
tide/low tidc time calculating method and a computer-readable
recording medium recorded with a program to execute the method
by a computer.
According to an aspect of the present invention, there is
provided an electronic tide meter according to a first structure
of the present invention, characterized by being provided with:
an input means for selecting a region and inputting a calendar;
a memory means for memorizing tide data for each region; an
operating means for determining with a first time interval
first tide level data from a tide level estimating equation
fixed by the calendar and the tide data specified by the
selected region, further determining second tide level data
with a second time interval ahorter in time interval than the
first time interval from the tide level estimating equation,
and calculating from the second tide level data a time that
desired tidal phenomenon occurs.
According to this structure, an operating means is
provided which performs two staged tide level data calculation
such that fzrsL Zide level data is determined with a first tim+
iriterval from a tide level estimating equation fixed by a
calendar and zide data for each region and further second tide
level data is determined with a second time interval shorter
in time interval than the first time interval, Accordingly,
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CA 02273730 1999-06-08
a range having precise information required can be selected to
determine tide level data with a fine time interval for that
range. It is zherefore possible to eliminate useiess.operati.ng
time and calculato with accuracy a time that, desired tide
phenomenon occurs.
Also, an electronic tide meter according to a second
structure of the present invention, in an electronic tide meter
for calculating a high tide time and low tide time by using a
tide level estimating equation fixed by an inputted calendar
and tide data of a selected region, characterzzed by being
provided with: an operating means for determining with a first
time interval first tide level data from the tide level
estimating equation, determining, when a sign in displacement
between successive ones of the first tide level data changed,
second tide level data from the tide level estimatzng equation
with a second time interval shorter in time interval than the
first time interval at around a time that the sign in
displacement changed, and calculating the high tide time and
low tide time from the second tide level data.
According to this structure, an opQrating means ic
provided which performa two staged tide level data calculation
such that first tide level data is detexmlned with a first time
intarval from a tide level estimating equation fixed by a
calendar and tide data for each region and further second tide
level d,ata is determined with a second time'interval shorter
CA 02273730 1999-06-08
in time interval than the first time interval. Accordingly,
a range having precise information required can be selected to
determine tide level data with a fine time interval for that
range thereby calculating a high tide time and low tide time.
=t is therefore possible to eliminate useless operating time
and calculate with accuracy a high tide time and low tide time.
Also, an electronic tide meter according to a third
structure of the present invention, in an electronic tide meter
for calculating a high tide time and low tide time by using a
tide level estimatxng equation fixed by an inputted calendar
and tide data of a selected region, characterized by being
provided with: an operati.ng means for determining with a first
time interval first tide level data from the tide level
estimating equation, and determining, when a sign in
displacement between successive ones of the first tide level
data changed, second tide level data from the tide level
estimating equation with a second time interval shorter in time
interval than the first time interval at around a time that the
sign,in displacement changed; and a ealeulating means for
determining an extresne value by interpolating the second tide
level data and calculating the high tide time and low tide time
from the second tide level_
According to this structure, an operating means is
provided which performs two staged tide level data calculation
such that first tide level data is determined with a first time
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interval from a tide level estimating equation fixed by a
calendar and tide data for each region and further second tide
level data is determined with a second time interval shorter
in time interval than tha first time interval. Accordingly,
a range having precise information required can be selected to
determine tide level data with a fine time interval for that
range. Further, a calculating means is provided to perform an
interpo].ation process on that tide level data. It is therefore
possible to eliminate useless operating time and calculate with
accuracy a high tide time and low tifle time.
Als,o, a high tide/low tide time calculating method
according to a fourth structure of the present invention, in
a high tide/low tide time calculating method for calculating
a high tide time and low tide time by using a tide level
estimating equation fixed by an inputted calendar and tide data
of a selected region, characterized by including: a first
process for determining with a first time interval fi.rst tide
level data from the tide lQvol estimating equation; a second
process for determining, when a sign in displacement between
successive ones of the first tide level data changed, second
tide level data from the tide level estimating equation with
a second time interval shorter in time interval than the f irst
time interval at around a time that the sign in displacement
changed; a third proccss for determining an extreme value by
interpolating the second tide level data; and a fourth process
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for calculating a high tide time and low tide time from the
extreme value.
According to this structure, two staged tide level data
calculation is performed such that first tide level data is
determined with a fir.~,t time interval from a tide level
estimating equation fixed by a calendar and tide data for each
region and further second tide level data is determined with
a second time interval shorter in time interval than the first
time interval. Accordingly, a range having precise information
required can be selected to determine tide level data with a
fine time interval for that range. Further, an interpolation
process is performed on that tidc level data. It is therefore
possible to eliminate useless operating time and calculate with
accuracy a high tide time and low tide time.
Also, a computer-readable recording medium according to
a fifth structure of the present invention, in a computer-
readable recording medium recorded with a program to cause a
computer to execute a high tide/low tide time calculating
method for calculating a high tide time and low tide time by
usinu a tide level estimating equatioxa fixed by an inputted
calendar and tide data of a selected region, the computer-
readable recording medium being recorded with a program to
execuze: a first procedure for determining with a first trme
intQrval first tide level data from the tide level estimating
equation; a second procedure for determining, when a sign in
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= = T
digplacement bQtween auccessiva ones of the first tide level
data changed, second tide level data from the tide level
estimating equation with a second time interval shorter in time
intarval than the first time interval at around a time that the
sign in displacement changed; a third procedure for determining
an extreme value by interpolating the second tide level data;
and a fourth procedure for calculating a high tide time and low
tide time from the extreme value.
According to this structure, two staged tide level data
calculation is performed such that first tide level data is
determined with a first time interval from a tide level
estimating equation fixed by a calendar and tide data for each
rogion and further second tide level data is determined with
a second time interval shorter in time interval than the first
time interval_ Accordingly, a range having precise information
required can be selected to determine tide level data with a
f ine time interval for that range. Further, an interpolation
process is performed on that tide level data. It is therefore
possible to provide a program that can eliminate useless
operating time and calculate with accuracy a high tide time and
low tide time.
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According to an aspect of the present invention, there
is provided an electronic tide meter, comprising: an input
unit for selecting a geographic region and inputting a
calendar date; storing means for storing tide data for each
of a plurality of geographic regions; and operating means
for determining first tide level data having a first time
interval from a tide level estimating equation dependent on
the selected calendar date and the tide data corresponding
to the selected geographic region, for determining second
tide level data having a second time interval shorter in
duration than the first time interval from the tide level
estimating equation, and for calculating from the second
tide level data a time that a desired tide corresponding to
the selected geographic region and calendar date occurs.
According to an aspect of the present invention, there
is provided an electronic tide meter for calculating when a
high tide or a low tide occurs, comprising: operating means
for determining first tide level data having a first time
interval using a tide level estimating equation for
calculating a tide level based on a selected calendar date
and a selected geographic area, for determining when a sign
of a displacement value between successive first tide level
data determined using the tide level estimating equation
changes, for determining second tide level data having a
second time interval shorter in duration than the first
time interval from the tide level estimating equation at
around a time that the sign of said displacement value
changed, and calculating a time of a tide dependent on the
second tide level data.
According to an aspect of the present invention, there
is provided an electronic tide meter for calculating when a
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high tide or a low tide occurs, comprising: operating means
for determining first tide level data having a first time
interval using a tide level estimating equation for
calculating a tide level based on a selected calendar date
and a selected geographic area, for determining when a sign
of a displacement value between successive first tide level
data determined using the tide level estimating equation
changes, for determining second tide level data having a
second time interval shorter in duration than the first
time interval from the tide level estimating equation at
around a time that the sign of said displacement value
changed, and calculating means for calculating an extreme
value by interpolating the second tide level and
calculating a time of a tide dependent on the second tide
level.
According to an aspect of the present invention, there
is provided a high tide/low tide time calculating method,
comprising the steps of: determining first tide level data
having a first time interval using a tide level estimating
equation for calculating a tide level based on a selected
calendar date and a selected geographic area; determining
when a sign of a determined displacement value between
successive first tide level data determined using the tide
level estimating equation changes; determining second tide
level data from the tide level estimating equation having a
second time interval shorter in duration than the first
time interval at around a time that the sign in the
displacement value changed; determining an extreme value by
interpolating the second tide level data; and calculating a
time of a tide dependent on the extreme value.
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According to an aspect of the present invention,
there is provided a computer-readable recording medium
recorded with a program to execute by a computer a high
tide/low tide time calculating method for calculating the
timing of a tide, comprising the steps of: determining
first tide level data having a first time interval using a
tide level estimating equation for calculating a tide level
based on a selected calendar date and a selected geographic
area; determining when a sign of a displacement value
between successive first tide level data changes;
determining second tide level data having a second time
interval shorter in duration than the first time interval
from the tide level estimating equation at around a time
that the sign of the displacement value changed;
determining an extreme value by interpolating the second
tide level data; and calculating, a time of a tide
dependent on the extreme value.
BRIEF DESCRIPTION OF THE DRAWINGS
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CA 02273730 1999-06-08
For a more better understanding of the present invention,
reference is made of a detailed description to be read in
conjunction with the accompanying drawings, in which;
Fig. 1 is a block diagram of an electronic tide meter
according to an embodiment;
Fig. 2 is a flowchart showing the operation of the
electronic tide meter according to the embodiment;
Fig. 3 is a diagram showing the operation of the electronic
tide meter according to the embodiment;
Fig. 4 is a diagram showing the operation of the electronic
tide meter according to the embodiment;
Fig. 5 is a flowchart for explaining tide level operating
process according to the embodiment;
Fig _ 6 is a flowchart for explaining a tide level operating
process according to the embodimcnt; ,
Fig. 7 is a view showing an example of displaying a high
tide time of the electronic tide meter according to the
embodiment; and
Fig. 8 is a view showiing an example of displaying a high
tide time of the electronic tide meter according to the
embodirnent-
DETAJJ.t En Pr$CgxpTTON OF THE PREFI-:RFn FmxnnTnTmwT
CA 02273730 1999-06-08
Explanations will be made below on an embodiment of an
electronic zi.de meter according to the resent invention will.
Incidentally, this invention is not limited to this embodiment.
In the electronic tide meter according to the present
invention, a tide level estimating equation is to be determined
based on a harmonic dissolving method, in determining an
objective high tide time and low tide time. Herein, the tide
level estimating equation is first cxplained.
In major coastal regions such as harbor and sea bathing
areas, it is usual practice for a public agency or other tide
observing station to open tv the public tide data natlve to the
region. The tide data as stated herein represents an amplitude
or delay angle of each basic wave which is determined by
identifying a Fourier series (harmonic resolving method)
represented by superposing basic waves from a tide level changc
graph obtained through measuring with a tide meter in -he
region, say in the coastal area. Here, thQ Fourier series to
be determined corresponds to a tide level estimating equation,
wherein particularly the above-statea amplitude and delay
angle is termed as a harmonic constant and each basic wave as
a divisional tide.
Tide phenomena occur, as well known, due to the tide
generating force as a ma j or factor caused by celestial bodies
such as the moon, sun, etc. However, because there include the
effects of coastal regional topologies, sea water temperature,
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CA 02273730 1999-06-08
etc -, regionally native tide data, i. e. harmonic cone tant , is
essentially required. Also, celestial positions of the moon,
sun, etc. are determined by a calendar having year/month/day, -
,A.ccordingly, in the tide level estimating equation, first
determined is a constant that meets the calendar.
Nexzly, in the tide level estimating equation, a constant
is determined according to an observation point to determine
a concrete positional relationship with a celestial body, that
is, positional information at a coastal region where a high/low
tide time is to be obtained. Finally, the tide level estimat5.ng
equata.on is expressed as a time function to determine a
regionally native tide level, a5 follows.
CEquation 1]
h(t) f; * H, * cos4(Voi + Uj) + a'i * t ' 8i ~
:-~
Here, gi represents a correction delay angle wherein g;.
= xi + al - L - 61 * S. Also, the affix i is the number
representative of a kind of divisional tide. H;, and Ki are
above-stated harmonic constants which respectively represent
a divisional tide mean amplitude and a divisional tide delay
angle (delay amount in phase) at the observation poinz, other
symbols represent, f;,, Vo;,, ui: the astronomical factor at a
uni.versal time 0 o'clock, 6i, the angular speed for each
divisional t7lde, al: the number of divisional tide waves, L:
the observation point longitude (west longitude east
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CA 02273730 1999-06-08
longitude -), and S: the standard difference in time at the
observation point.
Incidentally, the divisional tide means a wave caused due
to a tide generating force from each celestial body. In
particular the divisional tide is Purther divided on a certain
period basis into ones called periodic tides. For example, a
half day periodic wave (main lunar half periodic tide) due to
the tide generating force of the moon is called a M2 divisional
tide, and a half day periodic wave (main solar half periodic
tide) due to the tide generating force of the sun is called a
SZ divisional tide.
Here, it is required to fix the number of divisional tides
to be used in the tide level estime.ting equation. The greater
the number of divisional tides, thc higher the accuracy of a
high/low r.1de time to be operated- However, there is a
necessity to take into account an operation time and the number
of regional tide data to be used. For example, Sa, S. Qz, 01,
pl, Kl, (J,2, N2, V2, MZ, Sy, K2, M9, MS4 are selevted, and numbers
are affixed from 1. Thc divisional tide herein listed is a
periodic t,iBe based on the tide generating force from the sun
or moon, Alike MZ and SZ as above, for example Ql, 01, Pl and
Ki respectively define individual waves as a main lunar
elliptical-rate tide, main lunar diurnal tide, main solar
diurnal tide, sun-moon combincd diurnal tide.
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_ CA 02273730 1999-06-08
In Equation 1, by first deterrnining a region (observati.on
poi.nt), an observation point longitude L and an observation
point standard difference of time S are determined and further
harmonic constants (Hi, x;.) are determined for the respective
divisional tides. Next, -by determining a calendar,
astronomical factors fi, voi, U) are fixed for the respective
divisional tides. The number of waves al and angular velocity
6i of the divisional tide are numerals readily fixed in each
divisional tide.
This angular velocity ai is calculated by al *.Ta,, t a2 *
s,v + a3 * h,õ + a4 * paõ which is a combination of respective
changes per hour, i.e.
Tao = 150
= 0 _ 5A901652
hav - 0.04106864
pav = 0.00464181
and each integer parameter (al, a2, a3, a4), based on
celestial body movement, in T: solar mean time angle, s: lunar
mean iongitude, h: solar mean longitude, p: lunar close point
mean longitude. Here, al is used as the number of divisional
tide waves and one of integer parameters to determine the number
of divisional tide waves. For example, in the case of M2
divisional tide, (al, a2, a3, a4) _(2 ,-2 , 2, 0) and its angular
velocity 6i is exprQssed as 2 15 - 2 * 0.54901652 + 2
0.04106864 - 28.9941042.
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in this manner, because the angular velocity 6i is a value
previously deterrni.ned together with the delay angle ici for each
divisional tide, the positional information L and s at the
region is determined and at the same time the co:crection delay
angle gi, is also fixad in value. Accordingly, it becomes
satisfactory to at least prepare, as native tide data to the
region, angular velocity 6i for each divisional tide,
correction delay angle gl and harmonic constant Hi.
The astronomical factor V,,. (Greenwich reference) is
calculated by a2 * s+ a3 * h + a4 * p that is a combination
of s, h, p and integer parameters (a2, a3, a4) as was explained
in calculating the angular velocity 6i. Here, expressions are
made as:
s = 211 . 728 t 129 - 38471* (Y - 2000) + 13 . 176396 ~(D + L)
h = 279.974 - 0.23871* (Y - 2000) + 0.985647 * (D 4- L)
p = 83.298 - 40.66229 * (Y - 2000) t 0.111404 ~(D + L)
where, Y, D and L are numerals derived from the calendar, which
are represented as Y: dominical year. D: days elapsed f=om
January 1 of year Y, L: the number of bissextile days botween
the beginning of the year Y and the beginning of year 2000. In
particular. L= int [(Y t 3) / 4) - 500. Mere, int [] represents
an integer portion and L is dealt with as a negative value for
the year before 2000.
Also, the astronomica.l factor U; is expressed as u;, - c
wherein c is an integer parameter and ui is expressed as a series
CA 02273730 1999-06-08
of a trigonometric function- N is expressed, using a calendar
Y, D and L, as:
N - 125.071 - 19.32812 * (Y - 2000) - 0.052954 * (D + L)
ACCordingly, the sum of the astronomical factors Vo1 and U,, is
expressed e.3:
voi f UI = a2 * s + a3 * h + a4 p+ c + ui
which is a value to be determined by calendar Y, D for each
divisional tide. For example, in the case of M2 divisional tide
(i = 10) , Volo + U10 = - 2s + 2h + u10
The astronomical factors fZ and ui, for example for M2
divisional tide (i = 10), are respectively expressed as:
flo - 1.0004 - 0.0373 * cos N + 0.0002 * cos 2N
uxo = - 2.14 sin N.
By determining a region (observation point) and calendar,
h(t) is finally constituted as a sum of equat'ions
representative of tide levels each for divisional tide which
is a tide level estimating equation for calculating a tide level
at time t.
The electronic tide meter according to the present
invention funczions utilizing the tide level estimating
equation as explained above. Fig. 1 is a block diagram of the
electronic tide meter according to the present invention. In
Fig- 1, the electronic tide meter is configured by an input
section 14 enabling input of a calendar and region selection,
etc. from a utilizer, a central processing unit (CPU) 10 for
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CA 02273730 2006-02-03
colculating a high/low tide day time in accordance with the
requirement through the input section 14 from the utilizer, an
oacillating circuit 13 for generating a clock to drive the CPU
10, a ROM 11 stored with an operation program for the CPU 10,
etc. , a RAM 12 for memorizing a result of calculation by the
CPU 10 and a set state given by the utilizer, etc. and a display
section 15 for displaying a result of the calculation by the
CPU 10, etc.
The ROM 11 is further stored with tide data, for
example, an angular speed 61 for each divisional tide, a
correction delay ansTle g:L and a harmonic, constant Hi, as stated
above. The number of divisional tides used in the tide data
is determined by a memory capacity of the ROM 11.
Next, the operation of the electronic tide meter according
to the present invention is explained with reference to r.
flowchart shown in Fig. 2. First, the utilizer inputs through
the input section 14 a year/month/day (calendar) that a
high/low tide time is to be known (step S101).
Then, the utilizer selects, through the input gection 14 ,
a region of which high/low tide time i3 to be known from a region
list stored 1n the ROM 11 (step $102) _ This determznes angu=ar
velocities aj,, correction delay angles gt and harmonic
conatants Hx native to the selected region for respeczive ones
of the divisional tides.
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}
In the process of the step S101, if the inputted
year/month/day is for example year of y/m-th month/c1.-th day,
y ia converted into a dominical year Y (y - no converaionis
required if dominical year) , to calculate the number of elapsed
days from January 1 to a d-th day of a m-th month as well as
the number of bissextile days between the beginning of year Y
and the beginning of year 2000. This determines astronomical
factors fi, Voi and UL for respective divisional tides (step
8103).
By the above steps S101 - S103, first decided is a tide
level e5timating equation h(t) for determining a tide level at
a time Z. The electronic tide mQter of the present invention
is characterized by making a tide level operation using this
tide level estimating equation h(t) by two stages (step S104) .
Fig. 3 demonstrates a result of tide level operation in
the first stage. Fig. 4 shows a result of tide level operation
in the second stage_ Incidentally, in Fig. 3 only one part of
it is shown. First, for the first staged tide level operation,
tide levels at t= 0 - 24 o' clock are ca.lculazed with an tYme
interval for example of AT1 = 60 minutes. Thereupon,
simultaneously calculated is a tide difference df2 = h(t2) -
h(tl) between a tide level h(t2) presently (time t2) operated
and a tidc lcvel h(tl) lastly (at a time tl) operated. Further,
examination is made for difference in sign bezween the
present-time (time t2) tide level difference df2 and the
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_ CA 02273730 2006-02-03
last-tirne (time tl) tide difference dfl - h(tl) - h(t0) from
its further past tide level (t0). Incidentally, the results
of the above operation are sequentially stored into the RAM 12.
Here, if there is a difference in sign between the tide
differ4nces df2 and dfl, for a second staged tide level
operation, tide levels are again calculated with an interval
for example of taTZ = 20 minutes, as shown in Fig. 4. In this
case, the tide level (tO) of 2* AT1 before the present time
(time t2) is taken as a start time of the second staged tide
level opexation . It has been confirmed by the first staged tide
level operation that there existed, between the time tO
to the time t2, a time at which the sign of tide difference
changes, that is, a time point of inflection in the tide level.
Accordingly, in the second staged tide level operation, --he
tide level of between the time tO and the time t2 is dctcrmined
with a further shorter interval thereby making it possible to
derive a true point of inflection.
After deriving a true point of inflection in the second
staged tide level operation, a second staged tide level
operation is made again from the time t2, that is, tide level
is calculated with a time interval, of OT1,
The above step S104 process is explained with reference
to flowcharts shown in Fig. 5 and Fig. S. Fig_ 5 is a flowchart
to,conduct the first staged tide level operation, while Fig_
6 is a flowchart to perform zecond ztaged tidc level operation.
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First, in ctop S201, Ti (e.g. 60 minute ) is subatituted
for the time interval AT that is for determining a tide level
in the tidQ level estimating equation and an initial value 0
is substituted for the time t; t - 0 in this case represents
0 o=clock_ Subsequently, a tide level h(t) at that time t is
calculated by using the above-described Equation 1 (step S202) .
Next, determination is made on whether the time t is an
initial value (in this case, t= 0?) (step S203) . if t = 0 in
the Step S203, the tide level h(t) calculated in the steD 5202
is substituted for a tide level variable hi (step S209) . After
the step S209, the time t is put forward by a time interval AT
minutes (step S210), and the process is returned to the step
S202. This is corresponds to the initial process for
determining a difference in tide level, hereinafter referred
to_
If not t= 0 in the step S203, the tide level variable h1
is already stored with a value and the value stored in this hl
is substituted for the tide level variable hO. Subsequently,
the tide level h(t) calculated in the step 5202 3.s substituted
for the tide level variable h1 (step S204) . Next, determination
is made as to whether the time t is put forward by the txme
interval AT or greater from the ini.tial value (step S205) _
If not t> AT in the step 5205, a tide level differencc
is not determined and a result of operation hl - hO is
substituted for the differential variable dl (step S211).
CA 02273730 2006-02-03
After step S211, the time t is put forward by a time interval
AT minutea (atQp S212) , and the procesa is returned to the step
S202. This corresDonds to the initial process for determining
a sign of a diffQrencQ in tide level, hereinafter referred to.
if t > AT in the step 3205, the difference variable dl is
already stored with a value and the value stored in this dl is
substituted for a differential variable dO and subsequently a
result of the operation hl - hO is substituted for the
differential variable dl (step 5206). After step S206,
determination is made on whether the differential variables dO
and dl are coincident in sign (step S207). Incidentally, in
the step S207 of Fig. 5, SGN () is a function for obtaining
a sign_
In the step S207, if the signs of the differential
variables dO and dl are not coincident, it 1s represented that
an extreme value of tide level exists between this time t and
a time t - AT * 2_ The process enters to the second staged tide
level operation (step S220) - After processing the step S220,
the process is again returned to the step S202.
If in the step 5207 the signs of the differential variables
dO and dl are coincident, detexmination is made on wheth r the
time t represents a final value (step S208) . Here, the final
value represents a final value in a time range for conducting
whole-day tide level operation_ For example, where conducting
21
CA 02273730 1999-06-08
tide level operation of t 0 - 24 0' clock, the final value is
a value representative of 24 o'clock.
In step S208, if the time t does not represent a final
value, the time t is put forward by 4T minutes (step S213) and
the process is returned to the step S202. If the time t
represents a final value in the step S208, the tide le-vel
operating process, i.e. the process of step S104 of Fig. 2, is
ended.
Next, explanation is made on the second staged tide level
operating process in the step 5220 of Fig - 5- First, the time
t at a time point that the process enters to the step= S220 of
Fig. 5 is substituted for an end time sT1, and a time t - AT
* 2 before that time t is substituted for a start time STO (step
8301) . Further, for a time interval ATT is substa.tuted a time
interval T2 (e_g. 20 minutes) that is smaller than the time
interval AT in the first staged tide level operating process,
and the start time STO is substituted for a time tt. Also, 0
is substituted for a variablo representative i of an
arrangement number of a tide level arrangement variable td
(step s302) -
After processing the step S302, a tide level h (tt) at that
time tt is calculated by using the above-clescribed Fquation 1
(step S303), and the tide level h(tt) caloulated in the step
3303 is further substituted for the tide level arrangement
variable td[i] (step 5304).
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CA 02273730 1999-06-08
Next, determination is made on whether the time tt is equal
to the end time ST1 (step S305). In the step S305, if the time
tt is not equal to the end time ST1, a variable i is added by
1(szep S308) - The time tt is put forward by a tiztte interval
ATT minutes- (step S309) , and the process is returned to the step
S303. By repeating the series of process over from the step
S303 to step S309, the tide level h(tt) calculated with the time
interval ATT becomes stored in the tide level arrangement
variable td ( S. ).
In the step S305, if the time tt is equal to the end time
STl, interpolation operation is made using the value stored in
the tide level arrangement variable td(i) and a tide level
distribution equation is determined which is in a range of from
the start time STO to the end time ST1 (step S306). From rhe
tide level distribution equation determined in the step S306,
an extreme value is determined using, for example, a Lagrangian
three-point inverse interpolation method (step S307).
Further, a time representative of the extreme value is
calculated, thus ending the second staged tide level operating
process.
Consequenty, according to the operatl.on shown by the
flowcharts of Fig. 5 and Fig. 6 as explained above, a tide level
h(t) is determined as a fist staged tide level operation w'_th
a first time interval DT, a put--forward time t is backed by AT
* 2 at a time point that the displacement sign in the tide level
23
CA 02273730 1999-06-08
is changed to thereby again determine a tide level h(t - AT *
2 - t) as a second staged tide level operation with a second
time interval ATT having a value smaller than the time interval
AT, and an extreme value is calculated from that tide level.
After ending the second staged tide level operation, the fist
stated tide level operation is again entered whereby these
first and second staged tide level operations are repeated over
those of the whole-day time. Some extreme values (ideally four
extreme values) are finally obtained thus ending the process
of step 5104 in the flowchart of Fig. 2-
After ending the process of the step S104, a high/low tide
time is calculated from the obtained some extreme values (sLep
S105) . The calculated high/low tide time is displayed on the
display section 15 (step 3106).
Fig. 7 and Fig- 8 illustrate examples respectively
displaying a high tide time and a low tide time in the display
50 corresponding to the display section 15. In display area
51 of Fig. 7 and Fig. 8, year/month/day is displayed. This is
a display region for input confirmation in inputting
year/month/day by an utilizer, and also a display region for
selecting a region. Al3o, in the display region 52 a calculated
high tide time or low tide time is displayed. Further, a znark
is simultaneously displayed which is to discriminate whether
on high tide time and low tide time. Furthermore, in the diaplay
24
CA 02273730 1999-06-08
region 53 a grgph i3 displayed which is to discriminate whethez
on high tide time or low tide time.
According to the electronic tide meter as explained above,
in order to determine a=high/low tide time, a whole-day tide
level is first determined by a rough time interval so that a
tide level is again determined by a fine time interval for a
limited range having a time around which the sign in
displacement of the determined tide level changes, thereby
calculating an extreme value. It is therefore possible to
shorten operation time and at the same time obtain an accurate
high/low tide time.
In the embodiment as explained abovo, the second staged
tide level operation re-determined all the tide levels of from
a start time of the second staged tide level operation proccss
to an end time. In this time range, the tide level operation
may be ended at a time point that the tide level displacement
sign changes similarly to the first staged tide level operation
process, to determine an extreme value using the tide levels
before the ta.de level displacement sign changes.
Also, in the embodiment as explained above, the second
staQed tide level operation was performed in the course of the
first staged tide level operation process. However, after the
first staged tide level operation is all ended, the second
staged tide level operation process may be made based on the
result.
CA 02273730 1999-06-08
In the embodiment as explained above, although two staged,
time interval different tide level operation processes were
provided, a plurality of tide level operation processes Frith
a further shorter time interval may be prepared. In such a case,
the time interval can be similarly switched to conduct an
operation proceas to finally determine an extreme value based
on a result of tide level operation shortest in time interval.
Furthermore, the electronic tide meter according to the
present inventiorf is applicable not only for determining a
high/low tide time but also for a case of determining a time
that other tide phenomena occur.
Furthermore, the high/low tide time calculating method as
was explained in the embodiment can be memorized as a computer
program on an recording medium such as a magnetic disc, optical
disc, etc. so that a high/low tide time can be calculated by
reading out the program in a computer.
According to the first structure of the present invention,
an operating mean3 is provided which performs two staged tide
level daza ca,lcu].ati,on such that first tzde level data is
determined with a first time interval from a tide level
estimating equation fixed by a calendar and tide data for each
region and further second tide level data is determined with
a second time interval shorter in time interval than the first
time interval. Accordingly, a range havirlg precise information
required can be selected to determine tide level data with a
26
CA 02273730 1999-06-08
fine time interval for that range. It is therefore possible
to eliminate useless operating time and calculate with accuracy
a time that desired tide phenomenon occurs.
According to the second structure of the present
invention, an operating means is provided which performs two
staged tide level data calculation such that first tide level
data is determined with a first time interval from a tide level
estimating equation fixed by a calendar and tide data for each
region and further second tide level data Is determined with
a second time interval shorter in time interval than the first
time interval. Accordingly, a range having precise information
required can be selected to determine tide level data with a
fine time interval for thst range thereby calculating a high
tide time and low tide time. It is therefore possible to
eliminate useless operating time and calculate' with accuracy
a high tide time and low tide time.
According to the third structure, an operating means is
provided which performs two ataged tide level data calculation
such that first tide level data is detexmined with a fa.rst time
interval from a tide l vel estimating equation fixed by a
calendar and tide data for each region and further second t=de
level data is determined with a second time interval shorter
in time interval than the first time in'terval. Accordingly,
a range having precise information required can be selected to
determine tide level data with a fine time interval for that
27
CA 02273730 1999-06-08
range- Further, a calculating means is provided to perforn an
interpolation process on that tide level data. It is theref-ore
possible to eliminate useless operating time and calculate with
accuracy a high tide time and low tide ti.me.
According to the fourth structure of zhe present
invention, two staged tide level data calculation is performed
such that first tide level data is determined with a first time
interval from a tide level estimating equation fixed by a
calendar and tide data for each region and further second tide
level data is determined with a second time inzerval shorter
in time interval than the first time interval. Accordingly,
a range having precise information required can be selected to
determine tide level data with a fine time interval for t]hat
range. Further, an interpolation proces: is performed on that
tide level data. it is therefore possible to eliminate useless
operating time and calculate with accuracy a high tide time and
low tide time.
According to the fifth structure of the present invention,
two staged tide level data calculation i3 performed such that
first tide level data is determined with a first tizae interval
from a tide level estimating equation fixed by a calendar and
tide data for each region and further second tide level data
is determined with a second time interval shortmr in time
interval than the first time interval. Accordingly, a range
having precise information required can be selected to
28
CA 02273730 1999-06-08
dstermine tide level data with a fine time interval for that
range. Further, an interpolation process is performed on that
tide level data. It is therefore possible to provide a program
that can eliminate useless operating time and calculate with
accuracy a high tide time and low tide time.
29
