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  • Considerations on the low-altitude operations of the cruising-type AUV Gondou for seafloor photographic surveys.

    Nagasawa, Ryosuke; Tanaka, Kitoshi; Horinouchi, Ryoichi (2023)
    Report of Hydrographic and Oceanographic Researches
    The Japan Coast Guard AUV Gondou is a cruising-type autonomous underwater vehicle. The Gondou is equipped with a downward-looking camera system that potentially unveils detailed seafloor feature from a different perspective than acoustic observations. As the Gondou is designed to run at relatively high-speed for wide-range seafloor mapping, the vehicle has limited maneuverability in horizontal and vertical directions. These operational characteristics of the vehicle require careful considerations in the design of mission planning and predetermination of contingency avoiding behaviors. This technical report notes our operational efforts to conduct seafloor photographic surveys with the cruising-type AUV.
  • Accuracy verification of a vessel-mounted laser scanner and its application to hydrographic surveys.

    Tomihisa, Takeshi; Takahata, Ryota; Mori, Hirokazu (2023)
    Report of Hydrographic and Oceanographic Researches
    A technology has been developed to measure topographies and features on land in three dimensions using a vessel-mounted laser scanner while performing multibeam echo sounders. As a first step to examining whether this technology can be used in hydrographic survey for nautical charting, we tried to measure the coastline using a laser scanner. In this trial measurement, we devised procedures of bias value measurement and accuracy confirmation and verified the horizontal position accuracy of the point cloud data measured by the laser scanner. Accuracy verification showed that there was almost no difference between the position of point cloud data measured by the laser scanner in calm sea and the coastline measured by the kinematic GNSS, so we concluded it can be used to draw the coastline on nautical charts. On the other hand, the measurement accuracy was inferior in rough seas. In addition, measurement by laser scanner enables the precise measurement of the coastline such as wave-dissipating blocks and is expected to be applied to vertical clearance measurements under bridges and position measurement of buoys and fishing implements.
  • New analytical system for monitoring ocean conditions especially the sea surface temperature, with the aid of the remote sensing products of Himawari.

    Kasaishi, Masafumi; Nakahata, Kota (2023)
    Report of Hydrographic and Oceanographic Researches
    We have used the remote sensing products for sea surface temperature (SST) provided by the artificial satellites to monitor SST and to perceive ocean currents around Japan, as well as to publish the Quick Bulletin of Ocean Conditions. In September 2022, we changed the method from using the SST observed by NOAA and MetOp to using the SST observed by Himawari-8. We had directly received the signals of SST data observed by NOAA and MetOp using an analytical system with parabolic antenna. We replaced that with the new system witch receives SST data observed by Himawari-8 provided by the Japan Aerospace Exploration Agency (JAXA) via an internet site. The replacement could reduce cost and workload for maintenance. In this report, we describe the outline of our new system for monitoring SST and the characteristic of the new SST images. The new system receives the SST products observed by Himawari-8 from JAXA. The observation interval of Himawari-8 is every 10 minutes. The high frequency observation could reduce data blanks in a one-day composite image caused by cloud coverages in comparison with the previous products. The daily average value was selected for composite SST images in order to avoid improbable SST patterns resulting from the comparison with the daily maximum and minimum values. To assure the accuracy of the new SST images, we compared the new product against SST datasets based on the result of direct observation in several cases. The anomaly between new images and the CTD dataset of the Chiba light beacon in the Tokyo bay is approximately ±0.6℃ among the 10-28℃ in SST. In other case, the anomaly compared with the SST datasets of Kuroshio-Bokujo buoys off the coast of Shikoku is approximately -1.1℃ and mostly accorded at 17℃ and 29℃ of buoy-observed temperature, respectively. When comparing the water temperature data of NOAA and Metop with the water temperature data of Himawari-8, it was found that Himawari-8 was approximately 0.7 ℃ lower at water temperature 28℃, and approximately 0.4℃ at water temperature 5℃.
  • Initial study on the visualization of physical structures in the ocean utilizing the water column imaging of multibeam echo sounders.

    Nagasawa, Ryosuke; Horinouchi, Ryoichi (2023)
    Report of Hydrographic and Oceanographic Researches
    Modern multibeam echo sounders have come to be capable of recording entire underwater echo profiles. The multibeam water column imaging discovers the spatial and temporal distribution of acoustic scatterers in water mass, potentially providing essential information to elucidate dynamic processes occurring inside the ocean. This technical report considers a processing method to highlight characteristic acoustic patterns that result from oceanographic phenomena and applies the technique to data obtained by the typical Mills-cross echo sounders. The result shows distinctive mid-water acoustic anomalies of laminar and periodical patterns. The laminar pattern shows abrupt vertical changes in the echo intensity, which might correlate with the seawater profile obtained by XCTD. The periodical pattern exhibits a train of intertwined waves resembling shear instability like the Kelvin-Helmholtz billow. The result suggests the ability of multibeam echo sounders to visualize pycnocline in the water column, which would further advance physical oceanographic study in terms of analyzing the 3-dimensional spatial distribution of midwater acoustic scatterers.
  • Overview of the old and new IHO Data Protection Schemes

    Kajimura, Toru; Hattori, Tomonori (2022)
    Report of Hydrographic and Oceanographic Researches
    IHO S-63“IHO Data Protection Scheme” is the standard for protecting S-57 ENCs from piracy and unauthorized use. It has been used worldwide. Part 15 of the IHO S-100“Universal Hydrographic Data Model” is the upgraded version of S-63 and will be used for S-100 products, not only for ENCs, in the near future. This article gives comparisons between them and offers some considerations.
  • Presentation of parallels and meridians in the Maritime-domain-awareness (MDA) Situational Indication Linkages, UMISHIRU

    Okano, Hirofumi; Toyosato, Hiroto; Akiyama, Hikaru; Minami, Hiroki; Matsumoto, Yoshihiro (2022)
    Report of Hydrographic and Oceanographic Researches
    The Maritime-domain-awareness (MDA) Situational Indication Linkages, UMISHIRU, operated by the Japan Coast Guard, is a Web-GIS (Geographic Information System) featuring more than 200 items of marine information. Since being upgraded from the former Japan Marine Cadastre in 2019, UMISHIRU has covered global-scale information items, but it can overlay the parallels and meridians to a limited extent on the map. This paper describes a method for beginners to draw parallels and meridians beyond the limited range, and likewise to draw other geographic lines.
  • Presentation of depth information in the Maritime-domain-awareness (MDA) Situational Indication Linkages, UMISHIRU

    Okano, Hirofumi; Ito, Koji; Kamikura, Hideka; Kobayashi, Taiga; Minami, Hiroki (2022)
    Report of Hydrographic and Oceanographic Researches
    When thinking about general use in waters, depth information is one of the necessar y pieces of information. By using a Web-GIS system such as the Maritime-domain-awareness (MDA) situational indication linkages, UMISHIRU, this can be effectively achieved. Unfortunately, the UMISHIRU does not itself have the depth information in. In this paper, we describe how to compile the depth data of the J-EGG500 and ETOPO1 and present the depth information in the UMISHIRU for the beginning UMISHIRU user.
  • Statistical data of sea ice observation in the recent 30 years

    Egawa, Asato; Inazumi, Shinobu; Iizuka, Masashiro (2022)
    Report of Hydrographic and Oceanographic Researches
    Ice information center open every winter at the 1st Regional Coast Guard Headquarters. For safe navigation, we collect and analyze data of sea ice observations from C.G. offices, stations and relative organizations, and offer ice information as sea ice condition charts and navigational warnings. In this report, we summarize observation results of coastal sea ice stations from C.G. offices etc. in the recent 30 years.
  • Trial of creating of tidal current grid data for the Akashi Strait

    Muneda, Koji; Tsuchiya, Chikara; Ino, Kohei (2022)
    Report of Hydrographic and Oceanographic Researches
    The Japan Coast Guard Hydrographic and Oceanographic Department has provided data on tidal current, which is one of the ocean currents, as area information (tidal current grid data). In recent years, technologies related to the ocean have advanced, and new information such as detailed water depth data has been acquired. In addition, the mainstream method of providing tidal current grid data is digital, which has a high variety of information usages from printed matter. The Hydrographic and Oceanographic Department is conducting research to create new tidal current grid data corresponding to these. Between 2019 and 2020, the Akashi Strait was examined as part of first trial at creating tidal current grid data.
  • On the tidal current harmonic constants in Ise Bay

    Muneda, Koji (2022)
    Report of Hydrographic and Oceanographic Researches
    The tidal current harmonic constants in Ise Bay are owned by the Japan Coast Guard Hydrographic and Oceanographic Department and is a point-like one created by continuous day and night observation of tidal currents at fixed points. There is a grid-like one created in 2004 based on joint reserch with the Japan Hydrographic Association (2004, 2005a, 2005b). This time, as part of the research to create tidal current grid data, tidal current harmonic constants were created from the current direction and current velocity data observed by the Ise Bay Ocean Short Wave Radar operated by the Nagoya Port and Airport Technical Research Office, Chubu Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism. We examined these tidal current harmonic constants.
  • Optimized observation cycle for the tidal harmonic analysis

    Ino, Kohei; Tsuchiya, Chikara (2022)
    Report of Hydrographic and Oceanographic Researches
    The Japan Coast Guard observes the tidal time series using the Autonomous Ocean Vehicle (AOV) to precisely determine datum levels. As the AOVs utilize solar energy for their observation equipment, interruptions of observation caused by the power shortage due to decrease in the amount of sunshine in the winter becomes an operational issue. In this paper, we investigate whether short observations during interruptions or prolonged observation are effective to obtain reliable tidal harmonic constants. We found that short observations of more than 24 hours during interruptions or observations from the next year on the same date as the interruption make the tidal harmonic constants close to the value calculated from no missing data. The results of this study can be used as index for deciding the implementation of observation in winter or making plans for observation using AOVs.
  • Installation of a seafloor geodetic observation system on the S/V Koyo

    Yoshida, Shigeru (2022)
    Report of Hydrographic and Oceanographic Researches
    The Hydrographic and Oceanographic Department, Japan Coast Guard (JHOD), has installed an acoustic transducer on all of its survey vessels (excluding the S/V Tenyo) to conduct GNSS-Acoustic ranging (GNSS-A) observations. JHOD also installed a seafloor geodetic observation system on the new S/V Koyo(4,000 tons) commissioned in March 2021 to improve the efficiency of its GNSS-A observations. In this article, we report on the outline of the seafloor geodetic observation system installed on the S/V Koyo, the survey method and the resulting relative position between the GNSS antenna and the transducer, and the result of the test observation. The result of the test observation indicated that the horizontal components of the seafloor site position observed by the S/V Koyo agree with the trend of the time series estimated from our regular GNSS-A observations. On the other hand, the vertical component indicated the possibility of a positioning bias, which would necessitate further evaluation by continuing the GNSS-A observations using the S/V Koyo.
  • Trial to visualize the distribution and seasonal variation of ALB-measurable areas estimated from remotely sensed diffused attenuation coefficient data

    Ogawa, Haruka; Yamano, Hiroyuki; Sumiyoshi, Masanao (2022)
    Report of Hydrographic and Oceanographic Researches
    Efficient Airborne Lidar Bathymetry (ALB) surveys involve elaborate prior adjustments and operation planning processes based on a consideration of various relevant conditions. We attempted to visualize the distribution and its seasonal variation of the ALB measurable areas around Japan using a remotely sensed dataset of diffused attenuation coefficients, which represents the optical characteristics of the seawater, to help reduce the burden of the operation planning. The results showed that the maximum measurable depth at a certain spot seasonally varies and, subsequently, the distribution of the measurable areas varies as well. The estimated maximum penetration depths have proved to make a useful index for operation planning, while its future verification is required.
  • Developing the standard operating procedures of ellipsoidally referenced surveys at coastal waters in Japan: trials of bathymetric data processing and verification of their results†

    Okubo, Masaki; Sumiyoshi, Masanao; Ino, Kohei; Kobayashi, Kenta; Tsuchiya, Chikara; Rika, Nozawa; Kurita, Hirokazu; Ogawa, Haruka; Nagano, Katsuyuki; Yamano, Hiroyuki; et al. (2022)
    Report of Hydrographic and Oceanographic Researches
    In recent years, with the spread and improvement in the accuracy of kinematic GNSS positioning, ellipsoidally referenced surveys (ERS) have become practically possible, which in principle do not require tide observations during the bathymetric surveys. In this paper, as the first step of a trial to establish the standard operating procedures for ERS in Japan, we presented the practical operating procedures of bathymetric data processing in ERS and vertical datum model estimation, by using the existing bathymetric data in Tokyo Bay. In this case, the validity of the ERS operating procedures was verified by comparing the depths in the ERS procedures with those in the conventional procedures with tidal reduction.
  • On the calculation of the tide table

    Ino, Kohei; Tsuchiya, Chikara (2022)
    Report of Hydrographic and Oceanographic Researches
    This article reviews the algorithms used for various calculations such as predicting the tidal heights and currents for the tide table, using the tide table, and obtaining tidal harmonic constants.
  • Operation and observations of the Autonomous Ocean Vehicle (AOV.

    Ino, Kohei; Sugiyama, Shinji; Kon, Takahiro; Tsuchiya, Chikara; Nozawa, Rika; Ogahara, Hidemi; Yoshi, Nobuyoshi; Nakayama, Koichiro; Nagakura, Katsumi; Uchimura, Shinobu (2021)
    Report of Hydrographic and Oceanographic Researches
    Japan Coast Guard has been operating the Autonomous Ocean Vehicle (AOV) since 2016 in order to precisely determine datum levels and observe meteorological and oceanographic conditions. In this paper, we report the problems and improvements concerning long-term observation. Moreover, we review the tide level data processing method related to determining datum level precisely and show recent examples of meteorological and oceanographic observation.
  • Installation of seafloor geodetic observation system on the S/V Heiyo.

    Yoshida, Shigeru; Watanabe, Shun-ichi; Hashimoto, Tomohisa; Nakamura, Yuto (2021)
    Report of Hydrographic and Oceanographic Researches
    The Hydrographic and Oceanographic Department, Japan Coast Guard (JHOD) installed an acoustic transducer on the bottoms of the S/V Meiyo (550 tons) in March 2008, the S/V Takuyo (2,400 tons) in February 2010, the S/V Kaiyo (550 tons) in March 2012, and the S/V Shoyo (3,000 tons) in November 2012 and started sailing GNSS-Acoustic (GNSS-A) observations. The JHOD also installed a seafloor geodetic observation system on the New S/V Heiyo (4,000 tons) in January 2020 for more efficient and precise seafloor positioning. In this report, we discuss the outline of the seafloor crustal movement observation system installed in the S/V Heiyo, the position measurement method and the measurement results of the GNSS antenna and the transducer, and the results of the test observation
  • Historical nautical charts published by the Japanese Navy during the Meiji era and owned by domestic and overseas libraries and museums.

    Sato, Satoshi; Yoritaka, Miwako (2021)
    Report of Hydrographic and Oceanographic Researches
    We surveyed the Japanese nautical charts published in the Meiji era in the collections of domestic and overseas libraries and museums in 2019. As a result, we found the following new facts.The Tokyo National Museum has in its holdings the charts exhibited at the first and third National Industrial Exhibitions held in 1877 and 1890. The Leiden University Libraries in Netherlands own two volumes of the Dai-Nippon Kaigan Jissokuzu, the atlas of Japanese nautical charts that the Japanese Hydrographic Office compiled based on its own hydrographic surveys in its founding period.While it is known that the Kyoto University Museum owns many charts that were published in the Meiji era and stamped with “Donated by the Navy”, some documents of the National Archives revealed that these charts were donated by the Japanese Imperial Navy in 1911, upon request from the Kyoto Imperial University.
  • Coverage of a tide gauge for water level reduction.

    Tsuchiya, Chikara; Sato, Satoshi (2021)
    Report of Hydrographic and Oceanographic Researches
    In this study, we proposed criterion for the “same” tidal variation as a means of determining the acceptable range of the water depth error based on the water level reduction. The proposed criterion is 9 cm of the standard deviation of the difference between the observed tidal levels and the tidal levels in the survey area. In order to investigate the geospatial coverage where the criterion is acceptable, the standard deviation of the tidal level difference from 2013 to 2017 using the tide gauge data from the Japan Oceanographic Data Center was calculated. In most areas along the coast of the Japan Sea from Susa to Wakkanai, the standard deviation of the difference of the tidal level between the two adjacent tide gauges is less than 9 cm. However, this does not apply to the Tsugaru Strait and the Pacific Ocean from Shibushi to Hanasaki or the area where the Kurosio gets closer to the coast, or when the difference of the astronomical tide is large. This criterion can be interpreted as being within the permissible range of the water depth required for the Special Order of hydrographic surveys. In these areas, data from the reliable permanent tide gauge nearest to the survey area, instead of a temporary tidal observation just in front of the survey area, should be used for water level reduction.
  • The time of lower low water.

    Nakamura, Azusa; Tsuchiya, Chikara; Horinouchi, Ryoichi (2021)
    Report of Hydrographic and Oceanographic Researches
    In many waters around Japan, it is well known that, among the low tides that occur twice a day during the spring tide, the tide level is lower in the middle of the night in the winter and in the daytime in the summer. We pointed out the approximate time of the lower low tide and showed its spatial distribution in Japan using the tide prediction equation. It is shown that, on the Pacific coasts, the lower low tide of the spring tide appears in the winter nighttime and in the summer daytime, although on the Japan Sea coasts, the lower low tide of the spring tide appears in the winter daytime and in the summer nighttime. It is also shown that this tendency does not depend on the year.

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