Point St. George, Calif. Empire, Oreg. Fort Stevens. Oreg. Klipsan Beach, Wash. Destruction Island, Wash. NOTE. The arc of calibration is a sector of the circle of which the compass coil at the radio station, is the center; the bearings are from the station (clockwise). Compass bearings are reliable only when they fall within the calibrated arcs. 66 The above stations are noted on the charts by the symbol " N.R.C.” For a complete description of naval direction-finder stations together with directions for their use, see Hydrographic Office Publication No. 205, Radio Aids to Navigation. Radio bearings from other vessels. Any vessel equipped with radiocompass can give a bearing to a vessel equipped with a radio transmitter. Such service will generally be furnished when requested, particularly by Government vessels. These bearings, however, should be used only as a check, as comparatively large errors may be introduced by local conditions surrounding the radiocompass unless known and accounted for. CONVERSION OF RADIO BEARINGS TO MERCATOR BEARINGS The increasing use of radio directional bearings for locations of ships' positions at sea, especially during foggy weather, has made it particularly desirable to be able to apply these radio bearings taken on shipboard or sent out by the shore stations directly to the nautical chart. These radio bearings are the bearings of the great circles passing through the radio stations and the ship, and unless in the plane of the Equator or of a meridian, would be represented on a Mercator chart as curved lines. Obviously it is impracticable for a navigator to plot such lines on his chart, so it is necessary to apply a correction to a radio bearing to convert it into a Mercator bearing: that is, the bearing of a straight line on a Mercator chart laid off from the sending station and passing through the receiving station. On page 15 is given a table of corrections for the conversion of a radio bearing into a Mercator bearing. It is sufficiently accurate for practical purposes for distances up to 1,000 miles. The only data required are the latitudes and longitudes of the radiobeacons or direction-finder stations and of the ship by dead reckoning. The latter is scaled from the chart, and the former either scaled from the chart or taken from the list of radiobeacon and radio direction-finder stations found in the light list or H.O. Publication No. 205. The table is entered with the difference of longitude in degrees between the ship and station (the nearest tabulated value being used), and opposite the middle latitude between the ship and station, the correction to be applied is read. When bearings are taken from the ship, the sign of the correction (bearings read clockwise from the north) will be as follows: In north latitude, the minus sign is used when the ship is east of the radiobeacon and the plus sign is used when the ship is west of the radiobeacon. In south latitude, the plus sign is used when the ship is east of the radiobeacon, and the minus sign is used when the ship is west of the radiobeacon. To facilitate plotting, 180° should be added to the corrected bearing, and the result plotted from the radiobeacon. Mid. L. Should the position by dead reckoning differ greatly from the true position of the ship as determined by plotting the corrected radio bearings, a retrial should be made, using the new value as the position of the ship. Example. A ship in latitude 36°27′ N., longitude 130°03′ W., by dead reckoning, obtains a radio bearing of 77° true on the radiobeacon of the San Francisco Lightship located in latitude 37°45′ N., and longitude 122°41′ W. Entering the table with difference of longitude equals 72°, which is the nearest tabulated value, and opposite 37° middle latitude, the correction of 135' or 214° is read. The ship being west of the radiobeacon, the correction is plus. The Mercator bearing will then be 77°+214°-794°. To facilitate plotting, add 180° and plot from San Francisco Lightship, thus: 791⁄44°+180°=25914° which is the true bearing to lay off from the plotted position of San Francisco Lightship. If the bearing is from a radio direction finder station ashore, the signs will be reversed to that given above. 20° 21° 22° 23° 24° 25° 26° 27° 28° 55666 10 15 21 26 11 16 21 27 11 17 28 31 36 41 38 43 34 39 45 12 18 23 29 35 41 47 12 18 24 31 37 43 49 13 19 25 32 38 44 51 7 13 20 26 33 39 46 14 20 27 34 41 48 53 54 28 35 42 49 56 29 36 44 51 58 30 38 45 53 60 15 23 31 39 46 54 62 67777 66666 16 24 32 40 48 29° 30° 7 15 31° 32° 33° 34° 35° 36° 37° 38° 39° 8888 40° 10 41° 64 16 25 33 41 49 57 65 17 25 34 42 50 59 67 26 34 43 52 60 69 18 26 35 44 53 18 27 36 45 18 28 37 54 62 71 63 72 46 55 65 74 28 38 47 57 66 19 29 39 75 58 68 77 10 20 30 39 49 59 69 42° 10 20 43° 10 20 44° 10 21 30 40 52 70 47° 11 48° 49° 11 22 33 11 23 34 45 56 45 57 68 79 91 102 79 50 80 51 61 72 82 92 102 113 123 133 143 153 106 117 127 76 86 97 108 119 54 56 59 61 63 66 68 70 73 75 77 79 51 82 84 86 95 103 112 120 129 138 146 115 123 132 141 88 97 106 155 163 172 150 159 168 176 90 99 108 117 126 135 144 153 163 172 181 111 120 129 139 148 157 166 175 185 .92 102 160 170 96 106 116 125 135 145 154 164 174 183 193 128 138 148 157 167 177 187 197 130 140 151 161 171 181 191 201 164 174 184 194 205 167 177 188 198 208 151 179 189 138 149 159 170 180 191 201 212 140 151 162 173 183 194 205 216 143 154 165 176 186 197 208 219 145 156 167 178 190 201 212 223 158 170 181 192 204 215 226 Radiotelegraphic broadcasts of weather information, issued daily (Sundays and holidays included) by the United States Weather Bureau for the benefit of marine and aviation interests, are sent out from naval radio stations on the Pacific coast. For a complete description of this service see H.O. Publication No. 205, Radio Aids to Navigation, also Circular No. 13, Radio, issued by the United States Weather Bureau. FREE MEDICAL ADVICE TO SEAMEN BY RADIO The United States Bureau of Public Health maintains the following stations at which free medical advice by radio may be obtained direct: San Francisco, Calif., United States Marine Hospital No. 19. Governmental and commercial radio stations will transmit free messages addressed to any of the above stations. In order to avoid confusion and to make the practice uniform, all messages for transmission will be signed "Marine Hospital No. —", or "Public Health Service Relief Station No. -", as the case may be. All coastal stations operated by the Radiomarine Corporation of America offer free medical message service to ships of all countries. Messages received from masters of vessels reporting symptoms observed in a sick member of the crew are promptly forwarded to the nearest marine hospital where the case is diagnosed by the medical staff from the information given in the master's message. A course of treatment is then decided upon and suitable instructions are transmitted to the vessel. No charge is made for radiotelegraphic service of such messages when they are prefixed by DH MEDICO." The following is a list of Radiomarine Corporation stations on the Pacific coast: Medical advice radiograms must be checked and sent "DH MEDICO." Such radiograms will be given preference over all other messages except SOS calls. Radiograms must be signed by the master and state briefly but clearly the symptoms of the patient. For a complete description of this medical service by radio, see H.O. Publication No. 205, Radio Aids to Navigation. THE UNITED STATES COAST GUARD The United States Coast Guard is a military branch of the Government maintained for the purpose of enforcing the navigation and other maritime laws under the jurisdiction of the United States, rendering of assistance to vessels in distress, saving life and property, destroying derelicts and removing obstructions and menaces to navigation. These duties include the International Ice Patrol, the Bering Sea Patrol, flood relief work, patrol of regattas and marine parades, and rendering medical relief to deep-sea fishermen and to the natives of Alaska. The Coast Guard makes no charge for its services to vessels in distress and will respond promptly to all proper requests for assistance so far as the distribution and condition of its facilities will permit. However, it is not the purpose of the Coast Guard to compete or interfere with commercial enterprise in ordinary towing and salvage operations, but to confine its assistance activities to cases of actual or potential distress. Radio-equipped vessels requiring assistance may obtain the services of the Coast Guard by transmitting a request on the international distress and calling frequency, 500 kilocycles (410 kilocycles on the Great Lakes), to "Any Coast Guard Unit" (radio call NCU), or to any shore radio station addressed to "Coast Guard." Shore radio stations will forward to the Coast Guard all information regarding vessels requiring assistance unless such information is contained in a message specifically addressed elsewhere. If the following information is included in the original request for assistance it will place the responsible Coast Guard officer in a position to determine immediately the types and number of vessels required to render adequate aid; thus greatly facilitating the work of the Coast Guard and avoiding any unnecessary delay in the dispatching of assistance. 1. Name, type, and nationality of vessel. 2. Position, course, and speed (including drift). 3. Nature of trouble and condition of vessel, sea, and wind. 4. Number of persons on board. 5. State whether or not Coast Guard assistance is required. In cases of extreme emergency, when an "SOS" is broadcast, it is requested that the following procedure be followed by the vessel in distress. Approximately 10 minutes after transmission of the original distress message, transmit slowly, on the distress frequency, "MO" and own radio call for 3 minutes. This will enable Coast Guard vessels and stations in the vicinity to obtain direction finder bearings and accurately plot the position of the distressed vessel. Coast Guard administrative offices are located as follows: Seattle, Wash., Federal Building, Seneca 3100. San Francisco, Calif., Customhouse, Exbrook 7494. The telegraphic and radio addresses are "Coast Guard, Seattle", "Coast Guard, San Francisco ", etc. Coast Guard stations are maintained at the places named in the table following. The stations are fully manned throughout the year and are supplied with boats, wreck guns, beach apparatus, and all other appliances for affording assistance in case of shipwreck. Instructions to enable mariners to avail themselves fully of the assistance thus afforded will be found in the appendix, page 344. The Coast Guard stations are provided with the International Code Signals and are prepared to send or receive signals in that code or by means of the Semaphore Code, the Occulting or Flashinglight Code, or the International Morse Wigwag Code. Telephone facilities are available at the stations for the summoning of Coast Guard cutters, tugs, or other assistance, or for communicating with telegraph lines. LIST OF COAST GUARD STATIONS Official designation 1 Name of station State Pacific coast Locality Umpqua River___ _ _ _do_. Bolinas Bay. .__do_. 313 Point Reyes .__do_. 314 Arena Cove___ __do_. 316 Humboldt Bay---| 318 Port Orford_. 319 Coquille River___ Oregon__ 321 322 Siuslaw .__do_. 3/4 mile south of Point Lobos. Bolinas Bay. 2% miles east of Point Reyes Light. Near old lighthouse tower, north side South side entrance Coos Bay, about Water front, Yaquina Bay, Newport, North side entrance, Tillamook Bay. Cape Disappoint- Washington Fort Canby, north side entrance of |