In quality control procedures in oceanic data centers such as JODC (Japan Oceanographic Data Center) and MIRC (Marine Information Research Center), it is impossible to correct archived data without consulting data originators even when erroneous or extraordinary data are found. It is very hard to send all of such data back to the originators. When the data having unbelievable values are found, they would not be eliminated, but some error flags would be attached to them. However, the ultimate purpose of the data management agencies is to collect accurate and correct data as much as possible. We have tried to find error sources in procedure of data processing and data management, in order to improve quality of the data flowing into JODC. In this paper, the results obtained in the analysis on the dataset originating from the Wakayama Research Center of Agriculture, Forestry and Fisheries are reported. Most of the errors are found in the typing or punching processes. Most of the mistakes of this kind can be easily found by using a quality-control (QC) software designed by MIRC. It was found that the data quality of the Wakayama Research Center of Agriculture, Forestry and Fisheries was considerably improved after 1971.
After oceanic data were archived by a data management agency such as JODC (Japan Oceanographic Data Center), even if questionable data are found, it is hard to send such data back to their originator for correction. They would not be eliminated from the dataset, but some error flag is put on them. However, it is desirable to minimize the number of questionable data. We investigated error sources which often happen in data processing, collection and storage processes, in order to find the way to improve the quality of data flowing into JODC/MIRC system. In the previous paper (Nagata et al., 1999), we analyzed dataset obtained by the Wakayama Research Center of Agriculture, Forestry and Fisheries (WRCAFF), and found that errors are mainly generated in punching processes. In this paper, we report the results of the analysis on the database of the Iwate Fisheries Technology Center (IFTC). The data quality in IFTC was much improved after 1970, as just as in WRCAFF. Many duplicated data were found in the database of IFTC. Main cause of the occurrence of duplication is that they make two kinds of dataset (Coastal Lines and Offshore Lines), and that the data obtained at some stations were sometimes sent to both of the dataset. Check of duplicated data is important in data management. We discuss techniques of duplication check by referring the case of IFTC.
Deep-tow magnetic surveys provide detailed information about magnetization of the oceanic crust. This method, however, needs a longer measurement time than conventional sea-surface magnetic surveys, because a ship speed for the deep-tow surveys is restricted to 2-3 knots in order to keep a vehicle towing near the bottom against buoyancy on a towing cable. This sort of problem occurs not only on the deep-tow magnetic surveys but also on the other deep-tow surveys such as seismic reflection surveys, side-scan sonar surveys, and so on. As one of the solutions to that disadvantage, we have developed a new deep-tow observation system with multiple sensors which allows us to make efficient observations compared with a single measurement. In 1996, we conducted deep-tow surveys by that observation system off western Hokkaido (in the Japan Sea). The system consisted of a seismic profiling system, a proton-precession magnetometer and a side-scan sonar. The magnetic measurements were successful for three of four track lines. A summary of the results is shown below. 1) Deep-tow magnetic anomalies in the Ishikari Basin gradually increased with gradients of 18 nT/km and 29 nT/km toward ENE and NE, respectively. 2) An extremely large deep-tow magnetic anomaly (amplitude: 775 nT; wavelength: 8 km) was detected in the northeastern margin of the Japan Basin, while there was no obvious anomaly on the sea-surface. The results in the Ishikari Basin are consistent with sea-surface magnetic anomaly data obtained previously and during these surveys. The remarkable magnetic anomaly in the Japan Basin could be explained by the following two models inferred from seismic reflection data in the area: a) a layer with positive magnetization including a conical body; b) a layer with variable magnetization including negative or weak positive magnetization causing the negative deep-tow magnetic anomaly.
This paper introduced the newly developed Real-Time Shallow Wave Meter. The Real-Time Shallow Wave Meter is able to observe shallow water wave heights and periods with sufficient accuracy by measuring seabed pressure fluctuations. Observed data are transmitted to the on-land personal computer by wireless, and are displayed on it at the same time. When the wave height exceeds a critical value, the warning signal is displayed. Following improvements was recently conducted to the system. (1) Composite Cable for mooring and data communication was developed. (2) Application to the offshore observation was realized by using movable telephone system. (3) Application to the directional wave and current measurement was enabled.