GLOSSARY 



FOR 



ELECTRONIC NAVIGATIONAL AIDS 



[Some of the most frequently used terms in discussing electronic aids or sysfemsl 



STANDARD LORAN SYSTEM. — A long-range system of navigation by radio pro- 

 viding accurate lines of position or fixes at sea by pulse time-difference 

 measurement. 



LORAN STATION. — A radio transmitting station radiating timed or synchro- 

 nized pulse signals used in the Loran system. 



STATION CIRCLE. — The great circle on the earth's surface passing through two 

 synchronized transmitters. 



BASELINE. — The segment of a station circle between the transmitters. 



BASELINE EXTENSION. — The portion of the station circle not contained in the 

 baseline. 



LORAN HYPERBOLA. — A line on the earth's surface along which all points have 

 a constant difference in their distances from two transmitters. 



LINE OF POSITION. — A segment of an hyperbola. 



CENTER LINE. — The hyperbola which is the great circle perpendicular to the 

 baseline. 



TIME DIFFERENCE. — The time interval between the arrivals of any two syn- 

 chronized pulses. This value is read directly on the Loran receiver-indicator 

 installed in the vessel or aircraft. 



LORAN CHARTS. — Loran navigational charts published by the Hydrographic 

 Office, Coast and Geodetic Survey, and the Aeronautical Chart Survey, USAF, 

 for use aboard ships and aircraft, 



LORAN TABLES. — Loran tables provide coordinate information from which 

 Loran charts are constructed. The tables may also be used instead of the 

 charts for Loran navigation. 



RECURRENCE RATE. — The rate at which pulses are transmitted. 



PULSE LENGTH. — The length of the pulse wave form expressed in microseconds, 

 as measured at one-half peak amplitude. 



SKY WAVE CORRECTION. — The amount of time to be added or subtracted from 

 the indicated time difference to reduce a sky wave observation to the cor- 

 responding observation for the ground wave "line of position." Amount of 

 correction required is indicated on the Loran chart. 



RADIO DIRECTION-FINDING. — A radiolocation in which only the direction of a 

 station is determined. 



RADIOBEACON STATION. — A radionavigation station the emissions of which are 

 intended to enable a mobile station to determine its bearing or its direction 

 in relation to the radiobeacon station. 



MARINE RADIOBEACON. — A radiobeacon station whose service is intended pri- 

 marily for the benefit of ships. 



SIGNAL TIMER. — A mechanical device controlled by clocks and used to control 

 and program characteristics of radiobeacons. 



WARNING DEVICE. — A device which warns the radiobeacon operator of beacon 

 malfunction when the condition persists for more than 2 minutes. 



RACON. — A radionavigation system transmitting, in response to a predeter- 

 mined received signal, a pulsed radio signal with specific characteristics which 

 provides bearing and distance data. 



RAM ARK. — A radionavigational system transmitting signals continuously 

 which may be received by Radar. Provides bearing information only (experi- 

 mental). 



RADAR. — A radiolocation system where transmission and reception are 

 carried out at the same location, and which utilizes the reflecting or retrans- 

 mitting properties of objects in order to determine their positions. 



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