. Electronic navigational aids; loran, radiobeacon, and radarbeacon systems and loran, radio-direction-finder, and radar ship equipment. Loran; Radar. OCEAN ELECTRONIC NAVIGATIONAL AIDS 5 determined through the use of "ground waves," but, nevertheless, is still of a high order of accuracy. One of the surprising facts about Loran is that in a matter of 2 to 3 min- utes' time a navigator at sea can determine his position with an accuracy comparable to that obtained from good celestial observations, which require considerably longer to make and which entail somewhat laborious mathe- mat
. Electronic navigational aids; loran, radiobeacon, and radarbeacon systems and loran, radio-direction-finder, and radar ship equipment. Loran; Radar. OCEAN ELECTRONIC NAVIGATIONAL AIDS 5 determined through the use of "ground waves," but, nevertheless, is still of a high order of accuracy. One of the surprising facts about Loran is that in a matter of 2 to 3 min- utes' time a navigator at sea can determine his position with an accuracy comparable to that obtained from good celestial observations, which require considerably longer to make and which entail somewhat laborious mathe- matical computations. The accuracy of Loran fixes varies considerably, depending on the relative position of the navigator and the transmitting stations, the angle at which the Loran lines of position intersect and several other factors. A very rough rule of thumb has been stated to be that a Loran line of posi- tion has an accuracy of better than 1 percent of the distance of the navigator from the stations; thus a navigator 1,000 miles away from the stations would expect the line of position to be well within 10 miles of the proper position. As the stations are approached, the accuracy increases greatly, and along the Ionosphere. Figure 1-4.—Ground wave and sky wave paths. imaginary line between the two stations, or "base line", a line of position may have an accuracy of the order of several hundred feet. This feature has par- ticular practical value, inasmuch as the physical arrangement of Loran sta- tions is such that a navigator making a landfall usually will approach the shore in this highly accurate area of Loran service. Figure 1-5 shows the pattern that a family of Loran lines of position make with respect to their transmitting stations and points out the regions of accuracy. Figure 1-6 shows a vessel approaching a harbor along a line of position. Another important feature of Loran to the navigator is the reliability of the signals and the consequent removal of
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