魚群探知機単体記録の判別計数に関する研究-III

魚探記録中の記録像の解析

抄録

In order to design the mask and to count echo patterns by field data, the structure and characteristics of the group of element “SET” and the relationship between these charac-teristics and several factors were analyzed from field data obtained during the cruise of the Hakuho Maru (KH-69-4) in 1969.
1) Several groups of elements were extracted from the digital echo data by applying the linkage of elements. Furthermore, several SUBSETs where the method for decision of the next base point is different from that of SET were extracted from SET by the linkage map.
2) SETs are classified into three types (A, B2 and BM) by the number of SUBSET in SET (one, two and more than two).
3) The number of SETs of TYPE-B (B2+BM) increases in accordance to slice level decreases, and the number of elements of SET for TYPE-B was found to be more than that of TYPE-A. Especially, when the slice level is low the number of elements in SET increased.
4) From tests for determining the ratio of the number of TYPE-BM to TYPE-A+B2, the number of SETs of the latter were found to be more than that of the former in all cases.
5) The effect of ship speed on the number of SETs in 6 knots was not as considerable as that in 4 knots.
6) Moreover, two undesirable types of SETs, SET ELEMENT OVER and SUBSET OVER, were counted in each case, because these SETs are not suitable for application to design echo masks. The former is SET which has more than 118 elements, and the latter is SET which has more than 16 SUBSETs. These special SETs increased abruptly when the slice level becomes low.
7) From these analyses, it seems that 0.4 or 0.5 for slice level and 6 knots for ship speeds are optimum levels for designing of the mask and echo pattern counting.