As soon as the range line becomes visible, we must-comparing its form with the descriptions in sailing directions and in the manual "Lights and Shapes"-be sure we have correctly identified the range line. For this purpose, we take a bearing on it and compare this with the one in the manuals.

If we do not immediately succeed in accurately proceeding to a range line, it must be approached at an acute angle. Approaching at a large angle, as a rule, does not expedite correctly proceeding to a range line-it delays it.

Having fulfilled the requirement stipulated in Rule 25 of the Regulations for Preventing Collisions at Sea that a power-driven vessel must keep to the side of the fairway which lies on the starboard side of the vessel, it is first advisable to correctly proceed to the range line, then-if the width of the fairway, draft of the vessel and navigation conditions permit-to veer slightly to the right, later proceeding parallel to the range line, but somewhat to the right of it, all the while checking the danger to navigation through fixes and reference and danger bearings.

With wind and current, causing the ship to drift away from the range line, a course is differing from the direction of the range line (fairway midchannel) by the anticipated amount of total drift, always in the direction from which the wind blows (or from which the current flows). By carefully observing on which side the ship drifts from the range line, we can, through successive approximations, refine the initial set course.

4. Use of Radio Range Beacons

Radio range beacons emit so-called interlock signals of the telegraphic alphabet (for example, A and N, D and U, or B and V). The antenna system of the radio range beacon is tuned in such a way that when the ship is on one side of the equisignal sector, only one signal will be heard (for example, A), and on the other side-its opposite signal (in our example, N). When the ship is in the

equisignal sector, we will not hear one signal or another, but only the continuous sound of a single tone.

In piloting a vessel in a radio range beacon equisignal sector, its basic characteristics must be obtained from the manual Radiotekhnicheskiye sredstva (Electronic Gear): frequency (wavelength), recognition signal, which signals are transmitted in one direction or another from the equisignal sector, and the operating schedule. Having tuned any radio receiver of appropriate range or a radio direction finder, operating on omnidirectional reception, proceed to receive radio beacon signals. In accordance with the signal received, determine on which side of the equisignal zone the ship is located, and set a course to lock on its axis. These actions are repeated if the ship deviates from the axis of the equisignal zone (one of the radio range beacon interlock signals becomes audible again). The correctness of movement of the ship is checked by all available means (taking fixes on the ship, measurements of reference and danger depths and distances, etc.).

5. Marking Navigational Hazards, Fairway and Channels
with Floating Warning Beacons

Floating warning beacons-lighted and unlighted buoys and spar buoys-are used to mark navigational hazards (banks, shoals, reefs, shallows), fairways and channels, mine hazard areas, etc. Complete data on marking systems used in the Soviet Union are contained in the Opisaniye sistem navigatsionnogo oborudovaniya v vodakh Soyuza SSR plavuchimi predosteregatel'nymi znakami (Description of Navigational Systems in the Waters of the USSR, with Floating Warning Beacons), published by the Hydrographic Service. Data on marking systems used in foreign waters are contained in appropriate sailing directions.

Buoys and spar buoys may serve only as warning beacons, i.e., they are used for approximate orientation in a ship's position with respect to a navigational hazard, fairway axis, etc., but may not serve as reference points in determining a ship's position, since they drift with relative ease away from their designated positions due to storms, ice movements and careless actions of passing ships. Having discovered that a spar buoy or buoy is not in place or is absent, this must be immediately reported to the nearest branch of the Hydrographic Service.

Designated positions of buoys and spar buoys are indicated on large-scale charts. The watch officer must know in advance when and in what direction he must anticipate detecting them from the plot. If the spar buoy or buoy is still not visible at the moment when its detection was anticipated, this cannot serve as a basis for assuming that the ship is far from the navigational danger. Sudden detection of a spar buoy or buoy, not anticipated from the plot, usually indicates a dangerous DR error. In this case, immediate measures must be taken to avoid its dangerous consequences.

In the system of marking navigational dangers with respect to compass points, the north buoy or spar buoy is placed to the south of the navigational danger; it indicates: "Keep to my north." Correspondingly, the south buoy or

spar buoy indicates: "Keep to my south," the east buoy-"Keep to my east," and the west-"Keep to my west."

Cross buoys and spar buoys are placed at small navigational dangers and indicate: "I am riding on the navigational danger, you can pass me from either side."

In the system of marking the sides of channels and fairways, buoys and spar buoys of the right side are positioned on the right side of the channel (fairway) with relation to the track of a ship proceeding from seaward. They have odd numbers, are painted black, have a white light, and indicate to a ship proceeding from seaward: "Keep me to starboard." Buoys and spar buoys on the left side have even numbers, are painted red, have a red light and indicate to a ship proceeding from seaward: "Keep me to port."

In the system of marking of midchannels of fairways and recommended headings, midchannel spar buoys and buoys are used. They are positioned in the midchannel of the fairway or along the recommended heading and indicate: "Proceed from light to light."

Aids to navigation in rivers, lakes and channels, and also navigation and anchor lights on river boats are shown in Appendices 31 and 32.

CHAPTER VI

CELESTIAL NAVIGATION

SECTION 42. PREPARATION FOR OBSERVATIONS

1. Selecting Time and Celestial Bodies for Observations

If the sky and horizon are clear, determinations from the sun can be made at any time of day, but bearing in mind that large errors in observations are possible with altitudes of celestial bodies of less than 5-10°. It is best to measure altitudes of the sun every 1-2 hours, selecting for the observations lines of position with azimuth differences of 40-60°.

In determining the position of a ship from the stars, evening observations are begun at about the end of the civil twilight, and in the morning-somewhat after the beginning of the nautical twilight. The selection of stars for observations and their identifications are achieved with the aid of a star globe. For this purpose, first the local sidereal time tm (see Section 44, Paragraph 2) at the approximate moment the observations begin must be determined. By rotating the meridian ring of the Observer 1 (Fig. 82), adjust the globe so that the top pole (identical to the latitude of the observer) is above the point on the horizontal ring identical to him 2 (in the northern latitude-above point N, in the southern-above point S), and the axis of the globe forms an angle with the horizontal ring equal to the latitude of the position (the reading on the meridian

ring must be 90° - p). By rotating the globe around the axis, establish a reading, on the celestial equator scale beneath ring 1 of the meridian of the observer, equal to the local sidereal time t

Then select the combination of brightest stars so that their altitudes lie between 10° and 70°, and the difference in the azimuths of neighboring stars is as close as possible to 90° in determining from four and from two stars, or 120° in determining from three stars. Using the semicircular rings of the vertical circles of the observer 3 and indicator 4, obtain the azimuths and altitudes of the stars selected, and record them. Convert the azimuths from quadrant to circle basis, bearing in mind that the azimuth on a circle basis is measured from north (N) from 0 to 360° clockwise, if we view the globe from above. Calculate the compass bearings of the stars from Eq. (77).

2. Determining Clock Corrections

Compare the clock with the chronometer (following the second beats of the chronometer, note the simultaneous readings of the chronometer Tch and clock T) and calculate the comparison

From the daily variation in the chronometer w, derive its correction at the moment of comparison

=

uch ucho

+ WAT,

(111)

where AT is the time interval, in days, from the moment of the last determination of the chronometer correction from radio time signals to the moment of comparison.

Calculate the clock correction:

u = uch

+ C.

(112)

Repeat these actions after measuring altitudes. Use the mean clock correction for the calculations.

3. Preparing the Sextant

The sextant is a precision instrument-it may be damaged by moisture, abrupt changes in temperature, and jerks and jolts. The sextant may be held only by the handle or frame, and never by the index arm or mirror. The pair of screws, gear rack and tangent screw must be protected from shocks and contamination. In roughly adjusting the index arm, squeeze its handles to the limit and only then rotate it.