Radar has proved itself to be of great value as an aid to avoiding collision in low visibility, but the advantages are not so much useful in close-quarter situation, as to find dangerous circumstances to be avoided in the early stage. From this point of view, the only safe and accurate way of getting the necessary information for early avoidance by radar observation is to plot the movement of targets. We are convinced of RADAR PLOTTER shown in this paper, a device for plotting without using drawing instruments, being one of most convenient and effective plotting aid.

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When a ship receives an electric wave issued from a radio station, we can determine the position line of the ship by its direction. For the purpose to determine this, an intersection chart has been published from the Hydrographic Department of Maritime Safety Agency. To avoid the disadvantage arising from the intersection chart, I tried to determine the position line by the nomogram. The determing equation is : sinLcotα=cosltanl_0-sinlcosL ; Where α is the azimuth of the radio station from the ship, l_0 is the latitude of the station, l is the latitude of the ship, and L is the difference of the longitude between the ship and the station. In this case α and l_0 are known, l and L are unknown. Fig.2 and Fig.3 make a pair of nomogram. Method of application In Fig.2, marke the point of the value of α lying on the line cot α. Draw the straight line m passing through the point α. The line m and the line x intersect on the point A. The line m and the line tan l_0 intersect on the point B. Mark the point C of the value of l_0 lying on the line tan l_0. The segment BC is the value of |y|. In Fig.3, mark the point D of the value A lying on the line x, and the point E of the value |y| lying on the line y in the direction upward from O. The point F that intersects with the line DE and the curve l is the value of the latitude, say l. Mark the point G of the value |y| lying on the line y in the direction downward from O. The point H that intersects with the line DG and the curve L is the value of the difference of the longitude. Add the value H to the station's longitude or subtract the value H from the station's longitude. That is the value of the longitude, say L. Plot the several points (l, L) on the chart, and the line that goes through these points is the line of position. For another radio station, we can get another line of position. The point on which two lines intersect is the position of the ship.

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The error parallelogram, ellipse and circle are considered to be the error boundary of ship's positions. We have made reseach about these three kinds of the error boundary theoretically and mathematically. The accuracy of the fix is shown by the area of the parallelogram, for this area is in inverse proportion to the probability density. So by drawning the curves of constant area we have got accuracy contour maps of ship's positions fixed by cross bearing and transfered position line method. The error of the estimated ship's position is discussed in Appendix II.

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There are two ways of computing the D. Long. when we sail a long way crossing the equator. They are "Mercator Sailing" and the method of measuring each D. Long. Separated by the equator. The former makes it necessary to provide "Mercator projection table", while the latter is troublesome in its calculation. In order to overcome these difficulties we thought of another means, which is to calculate the D. Long. by substituting the "Half lat." of the higher one between the "Lat. from" and the "Lat. in" for the mean lat. This method, we pressume, will make the calculation easier and yet not lose the accuracy, and be of value in its practical use.

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We shall have a regulation for the safety of cargo-handling onboard before long and it will, I hear, follow the Docks Requlations, 1934 of England, which I introduce here. 1. legislative position of, internal and international 2. birds-eye view of it, compared with the convention, 1932 3. some cases about it We haue many to learn from this regulation-especially from its construction and operation. Now let us train our students enough to fulfil their duties on the cargo-handling on board.

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Paying out the chain cable longly when riding at single anchor, the advantage of which are both the absorbing of various shock on the ship on account of the circumstances and conditions and the increasing of holding power. Therefore, the longer the cables are payed out, the better the good anchoring as well known. The object of this paper is to give a moderate length of anchoring scope due to optimum form of representing in ordinary weather and, secondary, to investigate and treatise the following matters concerned with this. (1) Connection between the tension of the cable and the depth of sea, the horizontal forces. (2) Determining of total external forces on ship at anchoring. (3) Mooring force of chain cable holding of the ship.

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The change of trim and the resultant drafts due to adding or deducting weight have been determined by calculation as usually. In this paper the author suggests a method of determining, more simply and speedily, the above mentioned amounts by means of chart work. For the purpose two nomographic charts are drawn by modifying the hydrostatic curves of the ship. The above charts, as some examples, for 500 G.T. Fish carrier, 3,500 G, T, Refrigerated whale meat carrier and 17,000 G, T, whale factory ship are shown in appendix,

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Author invented as following formuias and measuring methods for pivoting point, drift angle and turning circle on the turning motion of actual vessels. These outlines of ideas illustrated diagrammatically in Figs 1. 2. 3. 5. 6. 7. Therefore, in Fig 1 [numerical formula] (1) Or, in Fig 2 [numerical formula] (2) Where, x is represented the distance between Pivoting point and fore-end of the base line (Δx) on the ship. And, let PG be the distance between Pivoting point and centre of gravity in the ship. Hence, Drift angle=tan^<-1>PG/R…(3) Then, in one scene of Figs 1. 3. Each element of advance and transfer are Yi and Xi [numerical formula] (4) Ant, let Δt be a interval in second of one scene. let t be timre in second for continuous scenes. let n be numbers that repeat scene of Figs 1. 3. (θ_n=Δθ_1+Δθ_2+…+Δθ_i+Δθ_n Figs 5. 6 give α method of calibration for n) if, y and Δx are constant. Advance and transfer of turning circle (A) are Y and X [numerical formula] (6) or [numerical formula] (8) These results by above formulas are shown in Figs 4. 5. 7. 8 and Tables 1. 2

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To lay a steamer alongside a pier with the aid of tugs, there are two cases-either tugs are employed as auxiliaries when the engine is in good condition or the steamer have to be tugged when something is the matter with the engine. The measures of employing tugs in each case are summarized as follows

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After the H-Bomb experiment at Bikini Atoll on 1 Mar, 1954 abandant contaminated fishing boats and tuna fishes were found by the official inspection at 5 ports Fig, 1 plotted by Dr, Eizo Tajima shows such a distribution, Fig.2 plotted by Mr.N. Arizumi represents the dispersal of radioactive dusts by air current. Fig.3 (the distribution of oceanic currents and contaminat waters in the Equatorial pacific) obtained by the Survey of Syunkotu-maru comparing each other the apparent differences were explained by the oceanic circulation and prevalent winds and refered to the safety of navigation with some notices.

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It should be remarked that the gusty storm in accompany with the passage (after its passage included) of cold front in winter causes the abnormal high pyramidal waves in the ugly seas (which is dangerous to fishermen and navigators), especially in the Oceanic frontal zone (boundary of watermasses and currents), Two examples (One off Kinkazan in the North Pacific on 26.Dec.1952, another off Dizozaki in the Japan Sea on 16 Nov.1952) were illustrated. (See Fig.1, 2, 3, 4)

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In this paper, I report the change of : the reflected power by distances from a 10, 000 ton cargo ship and from a 150 ton training ship. They are the representative examples of ships whose reflected power I have measured since June, 1954. It is clear that the change of the reflected power is the same as the result appearing in the first report. Next experiment is the measuring of the reflected power from a sailing pinnace. It is influenced by the direction of sails. In the end I have measured the reflected power from various objects on the shore to konw the influence of masts, yards and other structures on the deck.

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The Deep scattering Iayer (DSL) rises to the surface at sundown and sinks down against sunrise. So far it has not heen pcsible to allege any physical discontinuity at present known in navigational circles as an explanation of the phenomenon. On the other hand, as numerous marine organisms show uertical variations of immersion in connection with light, most authorities agree that this scattering Iayer must be formed by concertrated groups of Iiving organisms. In this article, we studied about the fundamental refraction of ultra-sonic sound to he cause to the difference of temperature and density of sea water, or the groups of livingplanktons.

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