International Meeting on Radio Aids to Marine Navigation
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3 i INTERNATIONAL MEETING ON RADIO AIDS TO MARINE NAVIGATION. An International Meeting on Radio Aids to Marine Navigation was held in London from 7th to 27th May 1946. Delegates from the following countries attended : Australia, Belgium, Canada, Denmark, Eire, Finland, France, Greece, India, Italy, Netherlands, Newfoundland, New Zealand, Norway, Poland, Portugal, South Africa, Spain, Sweden, United Kingdom, U.S.A., U.S.S.R. and Yugoslavia. i Vice-Admiral J.D. Nares, the President of the Directing Committee of the International Hydrographic Bureau was invited to attend as an observer, and was present at three of the earlier meetings. The following extracts from certain papers read during the meeting, or presented thereat, are reproduced by permission of the Chairman, Sir Robert Watson-Watt, on behalf of the British Ministry of Transport and the Admiralty. J. D. N. FIRST SERIES. 1. A technical appreciation of the various Radio aids to Marine Navigation (Document No. 28). 2. Hyperbolic Navigation (Document No. 15). 3. Charts for Radar and position fixing Systems (Document No. 25). 4. Gee (Document No. 16). 5. Loran (Document No. 17). 6. Decca (Document No. 19). 7. Consol (Document No. 13). 8. P.O.P.I. (Document No. 18). 9. Corner Reflectors (Extract from Document No. 22). 1.—A technical appreciation of the various Radio Aids to Marine navigation. (Document No. 28) P art I. INTRODUCTION. 1. This document is based on the report of a technical committee representing the Government Departments concerned in the United Kingdom and their scientific research establishments. 2. It summarises the properties of those systems of radio navigational aids which have a possible application to marine use. 3. Part II summarises the principal characteristics o f the various systems. These are divided into two groups. T a b le i.— Systems o f known performance, i. e. those which are at present in use (such as Medium Frequency Direction Finding) and those which have been used in opera tions during the recent war. T a b le 2.— Other systems, i.e. those which have been used in experimental trials and those of which the general principles have been demonstrated or which exist only “ on paper ” , and for which the figures of performance are known incompletely. 4. Fuller details of the systems are given in Appendices 1 and 2. Appendix 1 gives further details of the system in Table I of Part II ; appendix 2 of those in Table II. 5. This document should be read in conjunction with document No. 8* which discusses the basic navigational problems to which radio aids are applied, and with document No. 30 which outlines the trends of development of radio aids to marine navigation. 6. Reference should also be made to document No. 29 which describes the problem» of frequency allocation which arise in connection with radio navigational aids, and document No. 34 which sets out the band widths desirable for each system. 7. No attempt is made in this document to discuss the economic factors which will affect the adoption of any particular system. P a r t II. CHARACTERISTICS OF THE SYSTEMS OF RADIO AID TO MARINE NAVIGATION. 1. Tables I and II summarise the principle characteristics of the various systems. 2. In studying the tables the following Explanatory notes should be borne in mind. N o te i. An “ elementary ” system means the simplest version o f the system capable o f giving a position line only. N o te 2. All distances, except where stated, are in nautical miles (one nautical mile = 1.85 kilometer). N o te 3. Under “ Performance ” , the accuracy of the various systems is given on a statis tical basis. Under 50 % zone (columns 8 and u ) and 95 % zone (columns 10 and 12) are given the range of error or inaccuracy, within which 50 % and 95 % of all observations will lie. Except when stated, inaccuracies refer to a position line and not to a fix. N o te 4. In column 15, “ Possible marine use ” , the letters O, L, C and P have the signi ficance : O = Ocean aid ; L = Landfall aid ; C = Coastal navigation aid ; P = Pilotage aid. These terms are more fully discussed in document No. 8. N o te 5. The characteristics given in Table I relate to the systems as at present used. They take no account of possible modifications. The characteristics in Table II are in some cases conjectural. (*) Not reproduced. P a r t II. — TABLE I FIGURE IN BRACKETS REFER TO THE NAVIGATIONAL AIDS OF KNOWN PERFORMANCE (5) EXPLANATORY NOTES (Part II, pap. 2). 13 Ul OC U. O a. P MANCE FREQUENCY Power Is accuracy Possible of channels DAYTIME Reference BAND of NIGHT TIME REMARKS controlled required for mainly Marine Letter in SYSTEM GENERAL -.METHOD elementary transmitting on (General) system Limits of inaccuracy (3) by the Use GENERAL REMARKS system R a n g e ( 2 ) Limits of inaccuracy (3) Appendix 1 : (8 ) (9 ) R a n g e (2 ) Performances shipborne ( ) (4 ) 1 (over sea) (over sea) equipment 50 % Zone 95 % Zone 50 % Zone 95 % Zone (a) M.F. D/F shipborne Loop Type D/F » 300 miles 250-000 kc/s 1 1° 3» 25 miles 1° 3» Ground ray only Yes L. Reliable only within ground ray range. lb) M.F. D/F shorebased Adcock D/F 300-000 kc/s )) 1 1 5 00 miles 0.7° 2» 100 miles 0.7» 2» Applies to a No O.L. Two-way communication 1 0 0 -5 0 0 1.4» 4» good site channel necessary. miles over 5 00 miles 0.7» 2» (c) M.F. D/F shorebased Loop Type D/F Ou 300-000 kc/s 1 300 miles 0.7° 25 miles 0 .7 “ 2» Ground ray only No L. Two-way communication channel necessary. (d) ROTATING M.F. Rotating loop aerial 300 k c/s 1 1.5 kw. 300 miles 1“ 3° 25 miles 1» 3" Ground ray only • No L. BEACON C.W. or M.C.W. (e) GEE Pulse, time difference 20-85 Mr/s 1 3 00 kw. 100 miles 0.3 % 0.8 % Day and night No L.C. Range depends on height of (peak) of range of range the same transmitter aerial. ( 6 ) (7 ) (f ) STANDARD LORAN ;Pulse, time di(Terence| 1,750-1,950 k c/s 1 100 kw. 000 miles 0.2 % 0.6 % 0 -5 0 0 miles As for daytime (<’>) (7 ) No O.L.C. I (peak) or range of range 5 0 0 -1 ,2 0 0 0.3 °!o 0.9 % miles oï range of range DECCA I C.W. phase compar-compar 80-150 k c/s (8*) 2 ■ 2 kw. 300 miles 0.0 2° 0.05° 0 -7 5 miles Effectively as for day. Full perform No O.L.C.P. ison. Multiplicity of Use as Ocean or landfall aid (C.W.) 3 0 0 -1 ,0 0 0 lower Init useful 7 5 -2 0 0 miles Appreciably poorer ance figures not awaits completely satisfac frequencies. miles accuracy obtainable over than for day. yet available. tory svstem of Lane Identi 200 miles Serious errors due to ( 6) (7 ) fication. Pilotage facilities possibility of “ lane limited to within about 50 slipping ” at ranges miles from centre of chain. over 250 miles. <h) CONSOL Mod. C.w. 200-500 kc/s 1 2 kw. 1,500 miles 0.2° 0.6» 2 5 -5 0 miles As for daytime At night bear No O.L. Minimum range or 25 miles Rotating- equisignal (C.W.) 3 0 0 -5 0 0 0.5» 1.7» ings are subject within which the system pattern. miles to bias as well cannot be used. as fluctuations shown. (7 ) (i) RADAR (shipborne) Pulsed radar, p.p.I. 9.000-10,000 1 30 kw. Minimum range = 50 yards. + 25 yards -<-5 0 yards On largest scale Yes C.P. Merchant ships radar to Ihe j to U.K. specification display: Mr/s ■(peak) Discrimination — 50 yards in range. 1» bearing accur U.K. specification. — = 2» in bearing. acy. (j > RADAR (shipborne) Pulsed radar, P.P.I. 9.000-10,000 1 30 kw. Minimum range = 500 yards. -+■ 100 yds On largest scale Yes C. Type of P.P.I. radar set at Type 268 display. Mc/S (peak) Discrimination — 200 yards in range. ' ± 3» bearing accur present on loan to merchant — — 2» in bearing. acy. ship. (k) RADAR BEACONS Pulsed responder 9.000-10,000 1 or 2 10 kw. Performance controlled substantially by the shipborne radar. No C.P. Requires additional receiv beacon. 150-200 Mc/s 30 watts ing equipment in the ships. (peak) ( ) LEADER CABLES ; L.F. Induction field 1 20 c /s — 5 k c/s 1 about Range of 400 yards off the cable. Course relative to the cable can be determined Yes p. Vulnerability of cable to 1 kw. to an accuracy comparable with the steering limitations. displacement largely over come by modern methods. OTHER SYSTEMS FIGURE IN BRACKET8 REFER TO THE P a r t II. — TABLE 2 EXPLANATORY NOTES (Part II, par. 2). 1 4 5 6 12 13 14 15, PERFORMANCE FREQUENCY No. Power Is accuracy Possible i of channels • of DAYTIlME NIGHT TIME REMARKS controlled BAND required for Marine ! GENERAL METHOD I transmitting mainly (General) elementary on GENERAL REMARKS system Limits of inaccuracy (3 ) Limits of Inaccuracy (3) by the Use system R a n g e (2) R a n g e (2 ) Performances shlpborne (8 ) (9) ( 4 (I) (over sea) (over sea) equipment 50 % Zone 95 % Zone 50 % Zone 95 % Zone Pulse, time difference 180 k c/s 100 kw.