with

The mean quadratic error in the astronomical line of position m excellent observation conditions, is considered equal to 0.8-1.0 nautical miles for the sun and 1.0-1.5 nautical miles for a star.

5. Determining Compass Correction

A celestial body with the lowest possible altitude is selected (which can be observed directly through the telescope of a direction finder). In the absence of rolling, with direction finding using the folding mirror of an optical direction finder and making sure the azimuth circle of the repeater used in direction finding is level, the compass correction can be determined for celestial bodies the altitude of which is 30-40°.

Several (3-5) bearings are taken, each time noting the time on the clock. The local hour angle and declination of the celestial body are calculated. The DR azimuth of the celestial body is calculated using the VAS-58 tables, the TIPS-56 tables ("Tables of True Bearings of Celestial Bodies"), or special "Azimuths of Celestial Bodies" tables. It is converted to a circle basis and taken as the true bearing of the celestial body; the compass correction is obtained from Eq. (81). If an error exceeding 5-6 nautical miles is possible in the DR position of a ship, determination of compass correction using this method can be inaccurate.

CHAPTER VII

PRINCIPLES OF SHIP MANEUVERING

SECTION 45. BASIC MANEUVERING PROPERTIES

1. General Aspects

A vessel executing a maneuver with respect to a fixed or moving object is a maneuvering vessel. A vessel with respect to which a maneuver is being executed is the object of the maneuver. If this is one's own vessel, it can also be called the guide. If this is an enemy vessel, it is called the enemy or target.

Ordinarily a distinction is made between the following types of maneuvers of a ship or formation of ships: maneuvering with respect to a fixed object and maneuvering with respect to a moving object.

The position of the maneuvering vessel with respect to the object of the maneuver is determined by the bearing or relative bearing and distance.

The factors characterizing the change in the elements of the relative position of the maneuvering vessel with time are called maneuvering properties. Each has its own name: the range rate (RR), drift (Dr), bearing rate (BR), total range rate (TRR), and total drift (TDr).

RR is the rate of change in distance between the maneuvering vessel and the object of the maneuver, expressed in cables/min.

Dr is the rate of shift of the maneuvering vessel in a direction perpendicular to the line of bearing on the object of the maneuver, also expressed in cables/ min.

BR is the rate of change in bearing from the maneuvering vessel on the object of the maneuver in time, expressed in degrees/min.

TRR is the rate of change in distance between two maneuvering vessels.
TDr is the rate of shift of two maneuvering vessels.

Use of the basic maneuvering properties to solve problems is based on an approximate notion of the laws under which distance D and bearing B between ships change during a maneuver, whereby:

where Do, Bo represent the distance and bearing at the beginning of the maneu

ver, in cables and degrees respectively;

TRR is the total change in distance, cables/min; and

t is the maneuvering time, minutes.

2. Basic Maneuvering Properties With One Ship Maneuvering

With one ship maneuvering with respect to some object, the distance to the target and bearing on its change (Fig. 89), whereby:

where Vm is the speed of the maneuvering vessel, knots;
q is the initial relative bearing of the ship, degrees.

66 99

sign.

If q> 90°, RR has a "+" sign and if q < 90°, it has a
The drift of the vessel with respect to the object of maneuver

(128)

(129)

If the ship turns to starboard, Dr has a “+“ sign, and if it turns to port it has sign.

The change in bearing on the object of the maneuver:

BR = 57.3°

Dr
D

[degrees/min].

(130)

If the bearing change is clockwise, BR has a “+” sign, and if it is counterclockwise it has a "-" sign.

66

3. Basic Maneuvering Properties With Two Ships Maneuvering

When two ships are maneuvering with respect to each other, the distance between them and bearing change (Fig. 90), whereby the total change in distance

Vm
6

(- VK cos 4k). (131)

TRR = RRM + RR2 = (- cos qm) + (-/+ cos qx)

6

When two ships are maneuvering with respect to each other, the total drift:

A vector (vector quantity) is a parameter determined by its dimensions (length) and direction in space. Examples of vectors: force, speed and acceleration vectors.

Rule for addition of two vectors. In order to add vectors A and B, vector В must be transposed parallel to itself so that its origin coincides with the end of vector A. Vector C, the origin of which coincides with the origin of vector Д, and its end coincides with the end of vector B, is called the sum of vectors Д and B (Fig. 91):

Rule for subtraction of two vectors. In order to subtract vector В from vector A, both vectors must be drawn from one point and, connecting their ends, determine the third vector, equal to their difference. The difference vector is always drawn from the end of subtracted vector В to the end of diminished vector A (Fig. 92):

According to the kinematic theory of complex motion, the speed of absolute motion is equal to the geometric sum of the speeds of relative and transfer motion

Vabs = Vrel + Vtr

(135)

The motion of a maneuvering ship with respect to the locality must be regarded as absolute motion, and its motion with respect to the reference ship as relative motion. Motion of the reference ship itself with respect to the locality must be regarded as transfer motion.

We use the following designations:

7m - speed vector of the maneuvering ship (absolute speed vector);

Vk relative speed vector of the reference ship (transfer speed vector);

- relative speed vector.

Kinematic Eq. (135) applied to the maneuvering of two ships