Maneuverable tablet show the withdrawal distance in the diagram. Graphic plotting method, navigation in conditions of limited visibility, the influence of the operation of propulsors on the controllability of the vessel, control of the vessel and navigation safety, organization

Due to the impossibility of coordinated actions of ships (vessels) in conditions of limited visibility, the rules for divergence are given in the COLREGs not in categorical form, but in the form of recommendations. In accordance with Rule 19, a ship that detects another ship by radar must first determine whether there is a risk of collision. “If there is doubt as to the existence of a danger of collision, then it should be assumed that it exists” (Rule 7 paragraph “a”).

The choice of maneuver to avoid getting too close depends on the situation. The maneuver may involve changing course, speed, or both at the same time. The change in course and speed must be significant. Small successive changes in course and speed create difficulties in interpreting radar information on an oncoming vessel. By changing the speed we should mean reducing it or stopping the cars, since increasing the speed in conditions of limited visibility is contrary to the Rules.

Table 18.2. Tactical and technical data of some navigation radars

Changes of course to the left when another vessel is ahead of the beam, if this vessel is not the vessel being overtaken;

Changes in course towards a vessel located abeam or behind the beam.

Analysis of the situation and identification of elements of target movement (EDT)

The place of your ship K is considered to be in the center of the tablet;

Based on the bearings and distances measured by the radar after 1-2 minutes, at least two target locations are marked on the tablet;

Through the obtained points M1, M2, M3, a line of relative movement of LOD1 is drawn;

From the center of the tablet, a perpendicular KS1 is lowered onto LOD1, the length of which is the shortest divergence distance from the target DKV.

If DKp is greater than Doz, there is no threat of excessive (dangerous) proximity. No further calculations or maneuvers will be required until the target changes course or speed.

If DKp is less than Doz, the EDC is determined:

From point K they plot the velocity vector of their ship VK;

Rice. 18.1. Analysis of the situation, determination of the EDC and calculation of the divergence maneuver with a single target on a maneuver tablet

Time to approach the target at the shortest distance

The maneuverable tablet is placed on the table and the scale of the fixed range circles (RDCs) is coordinated with the circles of the tablet;

Distances are written on the circles of the tablet and the NCD is turned off;

Draw a ship course line on the tablet (considering your ship in the center) and combine it with the image course mark;

Fix the tablet and mark the initial locations of the observed targets on it;

After 1-2 minutes, at least two or three places of each target are applied to the tablet;

Draw lines of relative movement of each target.

Based on the location of the LOD and the DKp value, targets with which excessive proximity is possible are identified. Further processing of information for calculating EDC can be done as indicated above. To speed up the production of EDC, you can use the following technique:

The tablet with the target locations marked is shifted back along the course by the amount of distance traveled by the ship during the observation period;

New target marks are made, each time moving the tablet back along the course by the distance traveled;

By connecting the locations of the targets with a straight line, we obtain the direction of the vector of the true speed of each of them, directed from previous points to subsequent ones;

The magnitude of the true velocity vectors is calculated, as usual, through the distance traveled and observation time.

This method is less accurate than the previous one, but allows you to quickly assess the situation when encountering several ships.

If the radar has a true motion mode, it is possible to receive EDC directly from the indicator and quickly detect their change. However, on an indicator operating in true motion mode, determining DKp and Tcr is difficult, therefore, to accurately determine these values, it is necessary to switch to the relative motion mode.

The determination of EDC on large-scale maps (1:50,000; 1:25,000) is carried out in difficult navigation areas, where calculating the divergence maneuver only on a tablet can lead to the choice of a dangerous course. In this case, the navigator has the opportunity to navigate for himself and for the target in absolute motion without interruption from the navigation situation. In the case of using an auto-plotter, it becomes possible to have the current coordinates of your ship to conduct a plot for several targets and visually observe the situation.

The main disadvantages of this method are: the inability to quickly determine the danger of a collision; the shortest distance to the DKp target cannot be obtained directly from the pad; On the map you can only plot the point of intersection of the true courses. Therefore, simultaneously with the routing in absolute motion, it is recommended to analyze the situation and calculate the discrepancy on a maneuverable tablet using the Palma attachment and check the discrepancy on the map.

Calculation and control of divergence maneuver with a single target on a maneuver tablet

The preemptive position of the target Vt is calculated and plotted on LOD1; value М3Мц = Vрtс, where tс=2--4 min, depending on the operator’s training;

From point Mts, a tangent is drawn to the circle of the tablet corresponding to the given distance D03 and the divergence side; get a new line of relative movement of the target LOD2;

Two new speed triangles are constructed, for which, from the end of the vector Vm, a line parallel to LOD2 is drawn in the opposite direction (shown as a dotted line in Fig. 18.1) until it intersects with the circle of the tablet corresponding to VK;

From the resulting two vectors KK" and KK" choose the one at which the relative velocity vector Vp will be larger in absolute value and the course KK" will lead to a divergence from the target faster.

The maneuver is calculated in a similar way by changing the speed. After turning to the calculated course (changing the speed), observations of the target continue and the maneuver is monitored by marking target locations on the tablet. If the target locations fall on the LOD2 line, the maneuver is performed correctly. If target locations M5, M6, M7 lie on line LOD3, parallel to LOD2, this means that the turn began earlier than the calculated time and that the divergence will occur at a distance greater than D03. A change in the direction of the LOD, i.e., a shift in target locations to one side, indicates a change in the EDC, which will require new calculations.

Features of using HPLC "Ocean"

DKp is determined with an accuracy of 2-3 kb;

Tcr is determined with an accuracy of about 2 minutes;

The course of the oncoming vessel is determined with an accuracy of 5-10°, speed - from 0.5 to 1 knot.

The calculation of the divergence maneuver is carried out on the maneuvering tablet, as indicated above. The computing device allows you to simulate the selected maneuver (play it out in advance) and evaluate the possible results, while the LOD is displayed on the indicator screen.

The main options for divergence with a single target are given in § 23.11.

Calculation of a divergence maneuver with several targets simultaneously on a maneuver tablet

The most rational is the calculation with the construction of sectors of dangerous relative rates (COOK), proposed by O. G. Morev. The calculation of the maneuver using the proposed method is carried out as follows (Fig. 18.2):

With the detection of oncoming ships on the screen (targets No. 1, 2, 3), a relative position is followed for each of them on the maneuverable tablet;

Having carried out LOD and LOD2 and LOD3, having identified the danger of excessive proximity to one or more targets, their EDCs are determined (VM1, VM2_ and VM3);

For the target with the maximum relative speed (the approach to which will occur earlier by Dcr), the moment of its arrival in the pre-empted position is determined and the pre-empted positions of each target are plotted at this moment 1Mts, 2Mts, ZMts;

From the forward position of each target, tangents are drawn to the circle Doz, determining the dangerous sector (DS) of each target;

At the end of each true target velocity vector Vm1, Vm2, Vm3, a sector of dangerous relative courses is constructed;

To safely diverge from all targets, they simultaneously change their course or speed so that the end of their velocity vector VK is located outside the COOK.

Rice. 18.2. Calculation of a divergence maneuver with several targets simultaneously on a maneuver tablet

* In auto-tracking mode, the accuracy of determining the bearing and distance of the Ocean radar at distances of up to 16 miles is 0.5-0.7° and 30-40 m, respectively.

Forward
Table of contents
Back

LEGEND Vн
our ship's speed vector
Vв, Vс
speed vector of the oncoming vessel (observation object), target vector
Vo
relative velocity vector
Vн
the speed of our ship
Vв, Vс
speed of the oncoming vessel (observation object), speed of the target
Vo
relative speed
IKN
true course of our ship
IKts (IKv) true course of the oncoming vessel (observation object, TARGET))
IP
true bearing of the oncoming vessel (observation object)
KU
heading angle of the oncoming vessel (observation object)
D
distance to the oncoming vessel (observation object)
LOD
relative motion line
OLOD
line of expected relative movement
U
lead point
Dkr
closest approach distance
Ti
ship's observation time
Tkr
ship's time of arrival of ships at the point of closest approach
That
lead time
Fucking
ship's time, when, after performing the divergence maneuver, our ship can
return to the original elements of movement
tу

triangle until the lead point
tcr
time interval from the moment of taking the last point to build a speed
triangle (or from the lead point, if a maneuver is intended) to
the moment the vessels arrive at the point of closest approach
texp
the time interval from the moment of the lead point to the moment when, after execution
divergence maneuver our vessel can return to its original elements
movement

Applying ship echoes

Construction of the velocity triangle

in practice, bearing and distance measurements are made with some error, depending both on the technical characteristics

Brief conclusion on the topic.

CALCULATION OF DIVERGE MANEUVER

Lead point in 3 minutes.

Discrepancy within 3 mile zone

3 mile discrepancy

Changing the course and speed maneuver

Brief conclusion on the topic.

DIFFERENCE WITH SEVERAL COURTS

Attention!

Processing radar information includes a certain sequence of actions:
. surveillance and target detection;
. visual assessment of the danger of a radar proximity situation and selection of targets for radar plotting;
. radar plot - determination of elements of target movement and parameters of the approach situation;
. calculation of the divergence maneuver;
. control over changes in the radar situation during the maneuver until the vessels completely diverge.

Surveillance and target detection. The use of radar is most effective if radar surveillance is carried out continuously. In the open sea, constant observation should be carried out on medium scale scales of 8-16 miles with periodic viewing of the situation on scales of both smaller and larger scales. In confined waters, continuous observation is usually carried out on large scales with periodic reviews of the situation on small scales.

Visual assessment of the radar situation. Visual assessment is a mandatory stage in the processing of radar information and allows, with a large number of targets, to select dangerous and potentially dangerous targets for laying. The visual assessment is made using the afterglow trail, which remains on the radar screen behind the target echo signal and represents the previous trajectory of the relative approach of the ships. By mental continuation of the afterglow trace behind the target echo signal, a line of relative approach (LOD) is obtained, along which the distance of closest approach D cr is determined.

Visual assessment of the risk of collision can only be used when the navigator understands the principle of constructing the speed triangle, i.e. has sufficient skill to work on a maneuverable tablet.

When visually assessing the radar situation to identify potentially dangerous targets that become dangerous during the maneuver of one’s own ship and the target, it is extremely important to clearly understand the direction of the LOD turn that occurs as a result of these maneuvers.

All possible echo movement patterns cover the following three initial situations.
1. The echo moves parallel to our ship's heading line - this could be an oncoming ship, an overtaking ship, an overtaking ship, or a stationary target:
. when the speed of one or both vessels changes, the parallel movement of the echo signal is maintained;
. when the course of our vessel changes, the LOD turns in the direction opposite to the side of the turn;
. a turn of the LOD (afterglow trail), if our ship did not maneuver, indicates a change in the target's course towards a turn;
. The echo of a stationary target always moves parallel to our ship's course line.
2. The echo does not move parallel to the heading line:
- through the beginning of the sweep - there is a danger of collision;
- through the course line of our ship - the target crosses our course;
- along a line passing along the stern of our ship, - our ship will cross or has already crossed the course of the target:
. when changing the direction or speed of movement of the echo signal, if our ship did not maneuver, it is impossible to draw an unambiguous conclusion about the type of maneuver of the target. The type of maneuver can only be determined using a radar pad;
. turning our ship towards the target echo signal leads to a turn of the LOD from the stern to the bow of our ship;
. a decrease in the speed of our vessel leads to a turn of the LOD from the stern to the bow of our vessel;
. an increase in the speed of our vessel leads to a turn of the LOD from the bow to the stern of our vessel;
. turning our ship away from the echo signal does not allow us to visually assess the effectiveness of this maneuver (the relative speed of approach decreases, tcr increases, and as a result, a sharp change in the direction of the LOD can occur, determined only by radar plotting).
3. Echo does not move - satellite ship:
. the appearance of an afterglow trace parallel to the heading line - a change in the speed of one or both ships;
. a change in the courses of one or both vessels causes the appearance of an afterglow trail that is not parallel to the course line.

Radar pad. Relative spacer- performed on a maneuverable tablet by constructing a vector triangle of speeds. Using a relative plot, you can easily determine the elements of target movement and the parameters of the approach situation. Therefore, it is the main method used in practice.

The main thing that interests the navigator when detecting an object on the radar screen is how dangerous the observed target is.

The degree of danger is assessed according to two criteria:
1. D kr - distance of closest approach - the minimum distance at which the target can approach our ship if no one changes the elements of its movement (course and speed);
2. t cr - time interval to the point of closest approach - time interval from the moment of receiving the last target point, on the basis of which the line of relative movement of the LOD is constructed, until the moment the target approaches the shortest distance to our ship.

The smaller the Dcr, the more dangerous the approaching target is. But the degree of danger cannot be assessed only by the distance of closest approach. Equally important factors are the speed of approach and the amount of time the navigator has to maneuver and disperse at a safe distance. So, the situation of overtaking, as a rule, is less dangerous than divergence on oncoming (intersecting) courses, even if D cr in the first case is less than in the second.

The essence of the relative plotting is that we take our ship as the center of the coordinate system, which we place in the center of the tablet, and we mark the targets on the tablet at the corresponding points according to the bearing and distance measured using radar.

Step by step steps to assess the situation:
1. the speed vector of our vessel is plotted in the center of the tablet, equal to a 6-minute segment (for example, the speed of our vessel is 15 knots, set aside at a course of 1.5 miles);
2. measurements are taken of the bearing and distance of the oncoming vessel;
3. the measurement data is recorded in the table and the first point – A1 – is marked on the tablet;
4. "" is transferred in parallel to the resulting point sticks in"velocity vector of our ship;
5. After 3 minutes, steps 2-3 are repeated, the second point A2 is applied. The situation of approach is approximately assessed;
6. After another 3 minutes, steps 2-3 are repeated, the third point A3 is applied;
7. By connecting points A1 – A2 – A3, we obtain a line of relative motion - LOD;
8. From the beginning of our velocity vector we construct the vector V in, which is the vector true speed and heading of the oncoming vessel;
9. A perpendicular drawn from the center of the tablet to the LOD determines Dcr (in our case, Dcr = 1.7 miles). We find the value of t cr by plotting along the LOD segments equal to V 0 to D cr (here, approximately, 1.5 V 0 fits, i.e. t cr = 1.5 x 6 min = 9 min);
10. A decision is made on the choice of divergence maneuver.

Rice. 13.14. Construction of the velocity triangle

1. It is necessary to mark the lead point Y on the LOD - the position of the target at the moment of the start of our maneuver. Usually this is a 3-minute interval (distance A1 - A2).
2. From point Y we draw a tangent to the circle, the value of which corresponds to the given divergence distance (here 3 miles).
3. We transfer the resulting straight line of the expected line of relative movement OLOD parallel to itself to point A3.
4. OLOD “cuts off” part of our ship’s vector. The segment from the beginning of the vector to the point of intersection with the OLOD is plotted on the vector in the center of the tablet. This is the new speed of our ship, necessary to diverge at a given distance.
5. The reduction in speed must begin in advance - before the onset of moment Y, so that at this moment the ship already has a new speed.

Rice. 13.16. Speed ​​divergence maneuver

The speed divergence maneuver is applicable for ships with a displacement of up to 20,000 tons. In any case, when performing a divergence maneuver, it is necessary to take into account the maneuvering characteristics of the vessel.

When choosing a divergence maneuver with a dangerous target, when the echo signals of other vessels are observed on the screen, it is necessary to take into account those of them, the approach situation with which may worsen as a result of the selected maneuver. Such dangerous vessels are determined visually by the direction in which the vessel is turning during the intended maneuver. The peculiarity of the radar plot in this case is the need to conduct it simultaneously for all potentially dangerous ships. As a rule, a complete analysis of the situation is applied to the tablet until the end of the maneuver and return to the original parameters of your vessel’s movement.

GASKET ON MANEUVERABLE TABLET.

1. True gasket.

This plotting can be done directly on a large-scale route navigation map or sheet of paper. The essence of the method is as follows. Having discovered the echo signal of another ship on the indicator screen, determine its bearing P1 and distance D1, start the stopwatch, note the ship's time T1, the course of your ship Kn and the lag count OL1. By bearing and distance, the location of the echo signal A1 is plotted relative to its location, having previously selected the desired scale (Fig. 1). After a certain period of time (an interval of 3 or 6 minutes is convenient for calculations), observations are repeated (P2, D2, T2, OL2) and the locations of their vessel 02 and the observed vessel A2 are plotted. Drawing a straight line through points A2 and A2, we obtain the line of true movement of the target Kts.

By the distance between points A 1 and A2 and by time T1 and T2, you can determine the speed of the target Vc and calculate when and at what distance it will cross the course line of our vessel Tper and Dper.

To determine the distance of closest approach Dcr and the time before it tcr from point A2, the navigation of the vessel during the time between the first and second observations A2F=O1O2 is laid off in the direction opposite to its course. The segment O1C drawn perpendicular to the line passing through points A1 and F will be the distance of closest approach. The location of the ships at the moment of closest approach (points O1 and A4) can be found by parallel moving the segment O1C to position O4A4. Time of approach to the shortest distance

To determine the circumstances of the meeting and the elements of movement of the other vessel, two observations are sufficient. However, in order to exclude errors in observations and ensure that the elements of the movement of another vessel remain unchanged during the observation period, it is recommended to increase the number of observations. The presence of three sequentially plotted target locations (A1, A2, A3) at the same time interval on the same straight line and the equality of the distances A1A2=A2A3 indicate both the absence of errors in observations and the invariance of the elements of target movement in the period from T1 to T3.

The advantages of the true laying method include its clarity. The disadvantage is the relative complexity of the graphical constructions necessary to determine the main circumstances of the meeting: the distance of the shortest approach and the time before it.

2. Relative spacer.

This gasket has become widespread, since this method quickly and easily solves the main questions: at what shortest distance will the ships disperse and after what time. With relative positioning, the circumstances of the meeting and the elements of the target’s movement are determined in a moving coordinate system, the origin of which is taken at the location of the observer vessel. This corresponds to the actual picture observed by the navigator on the screen of the relative motion indicator.

From point O, taken as the place of one’s ship, the observed bearings P1 and P2 are plotted and along them the distances D1 and D2 (Fig. 2). The LOD is drawn through the obtained points A1 and A2. The length of the perpendicular OS, lowered from point O to the line of relative motion, represents, on the selected scale, the distance of closest approach Dcr. Time of approach to the shortest distance

With relative positioning, the distance at which the target will cross the course of our ship is also quickly determined. To do this, it is enough to measure the distance of the OP. (If the LOD passes along our bow, we determine the point of intersection with the target of our course, and if the LOD passes along our stern, the point where our ship intersects the target course, for which a line is drawn from the center of the tablet, parallel to the intersection with the LOD). The crossing time Tper is determined by adding the time interval tper to the readings of the ship's clock at the time the echo signal is located at point A2:

It must be recalled that first of all, the navigator must determine the main circumstances of the meeting, i.e. Dcr and tcr, and then determine the elements of the target’s movement.

The true movement of the target is the sum of two movements - relative

And the observer vessel or

Considering the commutativeness of the sum of vectors can be found

Two ways.

The construction of a vector triangle (see Fig. 2), shown by solid lines, is called direct. With it, the origins of the speed vectors (track lines) laid in the direction of the movement of ships are located at one point.

Sometimes the reverse construction is also used, in which the vectors laid aside in the direction of the movement of ships converge at their ends to a common point (shown with a dotted line).

In what follows, we will mainly use the direct construction, since it is more convenient when solving divergence problems.

The length of the motion vector of the observer vessel must be equal, on the selected scale, to the voyage of its vessel during the time between observations taken to construct the vector triangle. The length of the resulting target motion vector corresponds to the target's swimming during the time between observations.

3. Maneuverable tablet.

The maneuverable tablet is a grid of polar coordinates. To speed up calculations related to the navigation of the vessel during the time between observations, a logarithmic scale is placed on the maneuverable tablet. It is constructed as follows: on a straight line from the starting point, on a certain scale, segments are plotted equal to the decimal logarithms of numbers from 0.1 to 60 and digitized in the values ​​of these numbers. Since within 60 units, actions with minutes are similar to actions with numbers in the decimal system, any reading on the scale can be given the name “Time”, “Distance” or “Speed” and using the known values ​​of two of them, find the third one, solving the proportion

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When using a logarithmic scale, you should remember that the “upper” leg of the compass (set to large readings) always shows time, and the “lower” leg (set to smaller readings) always shows speed and distance.

From observations, the relative movement of the mark was established - 2.2 miles in 8 minutes. Find the relative speed.

We place the lower leg of the compass on the scale mark 2.2, and the upper leg on the scale mark “8”;

Without changing the compass solution, we move the upper leg of the compass to the “60” scale division. The lower leg of the compass will show the relative speed Vo=16.5 knots.

t=17 min, V=15 kt. Find the distance S.

We place the upper leg of the compass on the division “60”, the lower leg on “15”;

Without changing the angle of the compass, we move the upper leg of the compass to the scale division “17”. The lower leg of the compass will show the distance S=4.3 miles.

At V=17 knots the ship traveled S=8.7 miles. Determine the time it takes the ship to travel this distance.

We place the upper leg of the compass on the scale mark “60”, and the lower leg on the scale mark “17”;

Without changing the angle of the compass, we set the lower leg of the compass to the scale mark “8.7”. The upper leg of the compass will show the time t=31 minutes.

4. Selection and justification of a maneuver to diverge within a given distance.

If Dcr< Dзадто необходимо предпринять маневр для расхождения с судном-целью. Маневр выбирается на основании анализа ситуации в соответствии с МППСС-72 и обстоятельствами данного случая. Сначала судоводитель, глядя на вектор цели, воспроизводит в пространственном воображении существующую ситуацию и выбирает вид маневра (курсом или скоростью, сторону изменения курса). Сопоставляя tкр, VO и Dзад, выбирает время начала маневра. Последующая графическая прокладка служит для проверки безопасности выбранного маневра и уточнения его величины.

A graphical layout to justify the divergence maneuver at a given distance is shown in Fig. 3. It is carried out in the following sequence:

on the LOD, according to the expected time of the maneuver or according to the expected distance of the maneuver, point M of the target location at the moment of the start of the divergence maneuver is plotted;

by mentally turning the vector or changing its length in accordance with the selected type of maneuver, determine the direction of the LOD turn during this maneuver;

from point M, draw tangent to Drear OLOD, and of the two possible tangents to Drear, draw the one that corresponds to the turning side of the OLOD for the selected type of maneuver;

through the end of the vector parallel to the OLOD in the direction opposite to the direction of the OLOD, a line of the vector of the new relative speed is drawn;

if the course change maneuver is chosen, then the new direction of the speed vector of the observer vessel is found by turning the vector around point O1 until it intersects with the line of the new relative speed vector; the angle between the vectors will determine the required turning angle;

if a speed maneuver is selected, then the new speed vector of the observer vessel is equal to the vector segment from point O1 to the line of the new relative speed;

if a combined course and speed maneuver is selected, then to find the new course of the observer vessel, the vector of the observer vessel, reduced in accordance with the expected slowdown, is deployed around point O1.

5. Taking into account the inertia of the vessel.

When solving problems in previous chapters, it was assumed that the ship instantly changes its elements of motion and the LOD, during a maneuver, sharply changes its direction to the LOD. in reality this is, of course, not the case, and the inertia of the vessel must be taken into account.

Circulation accounting.

In accordance with NShS-82, the turning elements are presented in the table of maneuvering elements in the form of a graph and table when circulating from full forward speed to the right and left sides in cargo and in ballast with the rudder position "on board" (= 35°) and " half a side" (=15÷20°). When solving the problems of this chapter, it is assumed that the circulation diagrams shown in Fig. 4 for rudder shift = 20°. It should be borne in mind that the parameters of the actual circulation of the vessel may differ significantly from the table, depending on the speed of the vessel, its landing (list and trim), the ratio of draft and depth, the direction and strength of wind and waves.

When the observer vessel changes course (Fig. 5) relative to the location of the target, it will move along a curved trajectory from point M1 on the LOD (at the moment the observer vessel begins the maneuver) to point F on the OLOD (at the moment the maneuver ends). Subsequently, the target moves along the OLOD, shifted by a distance. The actual relative movement of the target will be more complex. Due to the drop in the speed of the observer vessel in circulation, the OLOD will not be parallel to the vector V01 until our vessel again picks up its original speed on a direct course. In this case, the drop in circulation speed is partially compensated by . In many cases (for example, when diverging from an oncoming target) due to a drop in the speed of the observing vessel while turning https://pandia.ru/text/80/090/images/image016_68.gif" width="600" height="369" >

1. Relative intermediate rate method.

From the graphic plot the required heading angle is found; from the table of maneuvering elements, using the turning angle, find the time spent by the vessel on turning, tman; intermediate course angle and intermediate swimming Spr; from point M1, the target position at the moment the turn begins is postponed during the turn; from the end of the vector in the direction opposite to the intermediate course, the intermediate voyage Sp is postponed; OLOD is carried out in parallel through the beginning of the vector Spr.

The method is accurate, but labor-intensive. When solving problems, discrepancies on the ship's bridge are not used. It is used when analyzing accidents and as a reference when assessing the accuracy of approximate methods.

2. Method of conditional pre-emptive point.

OLOD is carried out not from point M1 of the target location at the moment of the start of the maneuver, but from a conditional lead point M, carried forward along the LOD by the lead time t. As a first approximation, half the rotation time is taken as ttr. Thus, with this method of accounting for circulation, the turn of the observer vessel begins tupr~0.5 tman earlier than the target vessel arrives at the point from which the OLOD was carried out.

The method is most often used in practice. More accurate for opposing targets and less accurate for targets on converging courses. It is not applicable when turning under the stern of a satellite vessel, since in this case V0 = 0 and for any tsteer the points M and M1 coincide.

3. Method of introducing amendments to Dset.

As calculations show, when the course of the observer vessel changes by an angle of up to 90°, the errors in Drear due to the inertia of the turn do not exceed the tactical circulation radius. At large rotation angles the circulation diameter is reached. In this method, D is assigned with a margin for the maximum possible error from not taking circulation into account. This method is the main one when turning under the stern of a potentially dangerous vessel moving on a parallel or almost parallel course.

Taking into account inertia when maneuvering with speed.

Inertial characteristics of the vessel in accordance with NShS-82 are presented in the form of graphs constructed on a constant distance scale and having a scale of time and speed values. When solving the problems of this chapter, it is assumed that information on the inertial braking characteristics of a ship with a displacement of about 10,000 tons (ship I) and a ship with a displacement of about 60,000 tons (ship II), given in Appendix I, will be used.

As the observer vessel changes speed, the relative location of the target will move along a curved path, the curvature of which gradually decreases as the friendly vessel reaches the new steady speed. Errors from not taking into account inertia when maneuvering at speed can reach several miles, hence the importance of taking into account inertia. When maneuvering with speed on a large-capacity vessel, the new speed of the observer vessel is established after tens of minutes, and all this time the target moves along the LOD curve - hence the difficulty of taking into account inertia.

Taking into account inertia is possible in the following ways.

1. Method for constructing the OLOD curve.

The relative trajectory of the vessel's movement can be found by constructing travel triangles for successive time intervals t1, t2, ..., tn, after the maneuver So(ti) = Sc(ti) - Sн(ti)

To construct the OLOD curve it is necessary (Fig. 6):

from point M of Delhi's location at the moment our vessel begins to maneuver, draw a course line for the target and mark on it the segments traversed by the target at certain time intervals, for example, every three minutes (points B1, B2, ..., Bn); from points Bi, draw lines in the direction opposite to the course of the observer vessel, and plot along them the segments passed by the observer vessel during the corresponding time after the maneuver (points C1, C2, ..., Cn); draw the LOD curve through points Ci and determine Dcr as the shortest distance from the center of the tablet to the curve.

The method is accurate and visual, but labor-intensive. This method solves only the problem of predicting Dcr for the selected maneuver, but does not solve the problem of finding the required change in speed for divergence at a given distance. It is not used for solving problems under bridge conditions. It is used in accident analysis, and also as a reference for assessing the accuracy of approximate methods for accounting for inertia.

2. Method for introducing amendments to Dset.

If we take the tv characteristic as a measure of the vessel's inertia (The inertial characteristic tv is numerically equal to the time the speed drops by half during the STOP maneuver..gif" width="106" height="24 src=">.gif" width="67" height=" 22">.gif" width="34" height="22 src="> does not exceed 3 kb. In this case, Drear can be assigned with a margin for the maximum possible error. This method can be the main one for ships with a displacement of up to 1000 tons.

3. Method of conditional pre-emptive point (Fig. 7)

With this method of taking into account inertia, the new steady-state speed of the observer vessel is postponed in the speed triangle, but the OLOD is carried out not from point M1 of the target location at the time of the start of the maneuver, but from the conditional lead point M, carried forward along the LOD by the lead time ttr. As a first approximation, half the time during which the new speed of one’s ship is established is taken as ttr. Thus, with this method of taking into account inertia, the command to slow down is given ttr ~ 0.5 tman earlier than the target vessel arrives at the point from which the OLOD was carried out. If the lead time is chosen correctly, the OLOD will pass tangentially to the actual echo signal path.

With this method of taking into account inertia, it is conventionally assumed that during tup the previous speed of the observer vessel Vn is maintained (in this case the distance traveled is overestimated), and after that a new speed Vn1 is instantly established (in this case the distance traveled is underestimated). As can be seen from Fig. 8, the optimal lead time will be such that the overestimation of the distance traveled during the time ttr is compensated by the subsequent underestimation. This corresponds to the equality of the shaded areas in Fig. 8.

In Fig. 9 provides information on choosing the optimal lead time depending on the selected maneuver (Vn1/Vn=0 - STOP, Vn1/Vn=0.5 - MPH, etc.) and inertia characteristics tv. Based on this information, a lead time worksheet can be compiled at the start of the trip.

The vessel has an inertial characteristic tv=4 and has the following speed gradation: PPH 14 kts, SPH 10 kts, MPH 8 kts, SMPH 5 kts. Create a lead time worksheet.

PPH - SPH. Vн1/Vн= 10: 14 = 0.71. From the graph in Fig. 9 tup/tv=0.8; tcontrol=0.8*4=3.2~3 min. Calculating similarly for Vн1/Vн=0.57; 0.3; 0, we get for the maneuver of slowing down from full speed.

4. Medium speed method.

With this method of taking into account inertia in the speed triangle, it is not the new speed of the observer vessel that is plotted, but some average (equivalent) speed for the time from the beginning of the maneuver to the moment of closest approach The vector of average relative velocity is drawn through the ends of the vectors Vcp and Vc and parallel to it from point M OLODav is drawn (Fig. 10). In fact, the echo signal will move along a curved line located between the LOD and OLODsr with a convexity towards the LOD, and at the point of closest approach of the intersections of OLODsr.

As a first approximation, the arithmetic mean between the old and new can be taken as the average speed

If the time to closest approach () is short, the error will not exceed 10% of the ship's run-out during free braking.

More precisely, the value of the average speed can be found from the universal inertia accounting table given in Appendix 2. We will consider the use of the universal inertia accounting table with examples.

Find the average speed of vessel I during the time from the start of the PPH - MPH maneuver to the shortest approach, if tcr = 20 min.

From the braking distance graphs of vessel I (Appendix 1) for a speed of 16 knots we find tv = 4 min. In the universal inertia accounting table, in column tv= 4 we find the nearest tcr=22 min and in the corresponding line for reverse 0.5 Vn we get Vav/Vn= 0.6. The average speed can be put aside in the speed triangle by visually highlighting 0.6 segment Vn or, if necessary, converted into nodes Vav = 0.6 * 16 = 9.6 knots.

Based on the results of the radar plotting, it was found that in order to diverge from the target in Dback it is necessary to have Vav ~ 0.5 Vn. Based on OLODav and Voav, we determined the time from the beginning of the maneuver to the shortest approach tcr~20 min. Inertial characteristic of the vessel tv=8 min. What speed maneuver must be taken to diverge to Dback?

In the universal inertia accounting table, in the tv=8 min column we find tcr=19 min and in the corresponding line we look for the nearest smaller value of Vcr. In this case, Vcр=0.5Vн is in the “STOP” column. To diverge from the target in Dback, you must give "STOP". In the adjacent column we see that Vt/Vn = 0.25, i.e., in fact, by the time of divergence the speed will be 0.25 Vn.

Appendix 1A.

Vessel I displacement is about 10,000 tons.

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Appendix 2.

Compiled by sea captain Boriskin O.I. 2002

• 
  if the bearing of the target does not change and the distance decreases, then this target is dangerous and there is a threat of collision.
• 
  if the bearing and distance to the target do not change, then this target is a satellite, that is, a ship following the same course and distance.
• 
  if the bearing to the target changes and the line of relative motion (LOM) passes in front of the bow of the ship (see your vector), then the ship passes ahead of us and crosses our course
• 
  if the bearing to the target changes and the line of relative motion (LOM) passes behind the stern of the ship (see your vector), then the ship passes behind us and our ship crosses its course

1. 
   We put the goals on the tablet. Next to the marks we indicate the time (6). We circle the goals.
2. 
   Through the zero and sixth points of each dangerous and potentially dangerous target we draw LODs that extend a little further than the center of the maneuverable tablet.
3. 
   We complete the construction of the vector triangle. (Vectors only emerge from the rotation point of the vectors)
4. 
   We find the distance (Dcr) and time (tcr) of the shortest approach: the distance of the shortest approach is at the point where the vessel’s LOD touches a concentric circle from the center of the tablet. We mark the point of closest approach with a line perpendicular to the LOD. The line connecting the found point and the center of the screen is the distance of closest approach to this vessel. Let's find the time of closest approach for each ship. To do this, we measure the distance from the 6-minute point to the distance of closest approach using a meter solution corresponding to a 6-minute segment. We will indicate this time near the 6-minute mark of this vessel. After this we put a fractional line. Behind the fractional line you will need to indicate the time of crossing the course.
5. 
   Find the distance (Dper) and time (tper) of crossing the course.

1. 
   Let us determine the time it takes for the solution to cross the relative vector to the point of intersection of the course. The countdown starts from the 6th minute. We put the time of course crossing as a fraction after the time of closest approach (for example: 15/13)
2. 
   Analysis of the situation. The result of the analysis should be a maneuver. It must be remembered that only two maneuvers are allowed: slowing down and turning to the right. If a satellite vessel is following behind, the speed reduction maneuver is impossible. If there is a ship on the right, then the maneuver to turn to the right is undesirable, because this ship becomes dangerous. As a rule, the turning maneuver to the right is chosen. If it turns out that when turning to the right to pass a dangerous vessel, another vessel, potentially dangerous, becomes dangerous, then the turn maneuver must be calculated relative to this vessel.
3. 
   The calculation of the turn to the right maneuver is calculated at the time of the 12th minute, unless otherwise required. Therefore, it is necessary to set aside the corresponding 6-minute segments according to the ships’ LODs and mark off the vessel’s position on the LOD, which, as we believe, should be at the 12th minute. We do not circle the dot. The 12th minute is the beginning of the maneuver, so we put 12 in a circle next to the mark.
4. 
   According to the conditions of the task, a zone (distance) of safe divergence is given, which is marked with a circle on the tablet.
5. 
   From the point corresponding to the beginning of the maneuver (12 in a circle) of each dangerous and potentially dangerous vessel, we draw a tangent to the safe divergence zone. In this case, it must be taken into account that the ship will turn to the right, therefore, the tangent should be to the left of the ship. This tangent is the expected line of relative motion (OLOD), along which the ship will move in the event of our maneuver. The vessel will pass within the radius of the safe zone on the port side.
6. 
   Let's find the course that our ship should follow for each OLOD: using a parallel ruler, we move the direction of the OLOD to the 6-minute point (the end of the relative speed vector) and draw our new vector in the direction opposite to the OLOD. From the point of rotation of the vectors, using a compass solution, we mark a point on the plotted vector. Determine the lapel angle. After determining the turning angle for all targets, we determine the turning angle based on the largest one. We will part ways with this ship, and lead the rest.
7. 
   Using a parallel ruler we transfer the vector of our new ship to the center of the tablet.
8. 
   Let's transfer the vector of our ship to a new one to the 6-minute point of other targets for control and use the new vector to find the vector of the relative motion of the vessel new . It should not be aimed at the center of the tablet and should not pass closer than the specified minimum approach distance. Thus, we calculated the collision avoidance maneuver.
9. 
   Let's calculate the moment of completion of the evasive maneuver. After the evasion is completed, the ship will return to its previous course. The moment when this can be done must be calculated graphically: the ship will turn to its previous course, therefore the target marks on the radar screen will move parallel to the LOD before the maneuver. In this way, it is possible to determine the time to return to the previous course after passing targets at a safe distance. The end point of the turn-around maneuver can be determined for each target by crossing the OLOD and moving a parallel line of the LOD of each vessel, drawn tangentially to the safe divergence distance (radius of the danger zone, given distance). Having found the end points of the maneuver for each target with the appropriate solution new(!!!) vector of the relative motion of the vessel, we calculate the end time of the turning maneuver, put this time near the found point and circle it. The longest time will be the actual time to return to the previous course.
10. 
    Let's calculate the distance of departure from the original course. Let us subtract the start time of the maneuver from the end time of the maneuver. Let's get the maneuver time (totx). Let's find the distance traveled. To do this, we will use the logarithmic table “Distance-time-speed” on the right side of the navigation tablet. Using a meter solution, take the distance on the ruler between the number “60”, corresponding to the upper edge of the ruler and the speed number of our ship, apply this solution with one meter pad to the number corresponding to the time of the maneuver, with the other meter pad we determine the distance by which the ship deviated from the previous one during the maneuver course. The distance traveled can be found graphically: let’s plot the time tthm along our vector in 6-minute segments. We plot this segment on our new vector and from its end we lower a perpendicular to the vector of our ship. The value of this perpendicular (the distance from the end of the segment to the course of our ship) is equal to the deviation of the ship from the ship's course in miles (Dth).