Fumio MAEDA’s scientific contributions

The Persian Gulf route is one of Japan's most crucial trading routes. The accuracy of Omega system on the route is, therefore, to be studied closely. This survey was conducted on the relative accuracy of Omega system with respect to various position fixing methods presently used. These are the findings : 1. On the whole, the average relative error was 2.2 miles. 2. The average relative error in each of the 3 areas was 2.0, 2.2 and 2.8 miles, although the number for each area is based on a different amount of data. 3. Among all the combinations of paired stations used on the route, the average relative error for AE-BH, AE-AH, and AE-EH, though these paired stations are the ones most frequently used, was 1.9, 2.5, and 2.8 miles. 4. Lane error for pair BE has positively deviated distribution. The rest of the pairs showed widely dispersed distribution and their peaks were in the negative side. 5. Large relative errors occured in the South Chine Sea and the Arabian Sea.

The OMEGA system was studied to get practical information on its coverage, reliability and accuracy. A survey on the relative accuracy of the system was conducted in terms of selected pairs and their combinations. These are the findings : 1. It might be possible to evaluate the relative accuracy of OMEGA system by comparing OMEGA positions with radar positions. 2. Day time data shows the best relative accuracy. 3. Observed lane numbers for AB and AC are smaller than those for reference positions. 4. Relative accuracies for pairs are different depending on the time of day.

The accuracy of the OMEGA System is dependent upon the phase stability and predictability of phase variation. To get practical informations on coverage, reliability and accuracy of OMEGA System, Survey on the relative accuracy of the system was conducted in terms of selected pairs and their combination. These are the findings: 1. No pair combination gave relative error average of greater than 3.5 miles and its average was 2.5 miles. 2. In area 13, pairs AB, AE, AF, EF tend to show 5 to 9 cel in excess as an average and BE, BF, 2 to 4 cel in short. 3. Pair combination BE-BF, BE-EF, BF-EF showed relative error average of less than 2 miles. 4. These values change when data are specified with time; day, night or transient.

At present, the OMEGA system has seven stations in full operation and can be used extensively in the world. The accuracy claimed by this system is 1 mile during the day and 2 miles at night. The users of the system, however, have little knowledge about how accurately this system works, which gives rise to the lack of their confidence in this system. This report shows the result of the survey made on the relative accuracy of the system in terms of three parameters, individual ship, area and standard method. The survey started in April, 1977 in cooperation with the marine section of the Sanko steamship company. The result based on about 1200 observations so for obtained shows that the characteristics of the relative positional error is rather similar in all the areas, is different among the ships and is the mixture of the above two with method, i.e. there are different group of the methods in which the characteristics is similar.