In recent years, climate change has emerged with serious consequences in many regions of the world. Materials released into the ocean by human activities are diversifying, and the abundance in the ocean continues to increase. In such a changing marine environment, technological innovations in oceanographic observation are progressing rapidly. On the other hand, it is required to share these technologies properly in the community and provide data that guarantees traceability and comparability. It is also essential to hand down these technologies and the basic knowledge to the oceanographers of the next generation.
The Oceanographic Society of Japan (JOS) has established an editorial committee for Guideline of Ocean Observations to capture the latest trends in ocean observation and provide the community with state-of-the-art guidelines. JOS decided to make this guideline both in Japanese and English, so that not only ocean scientists in Japan but in other countries can share those knowledges.

The first edition of Guideline of Ocean Observations was published in September 2015 with an overview of oceanographic observations and the latest oceanographic and analytical methods. After that, two revisions were made, and by April 2018, a total of 10 volumes and 40-chapter guidelines were arranged. In this 4th edition, 12 chapters are newly added, and the contents of almost all chapters are satisfied. In addition, two chapters have been updated in this edition. For this guidelines, 44 authors working on a broad area of oceanography are involved in the writing. We hope that these guidelines will be used by many researchers around the world and contribute to the advancement of oceanography.

Editor in chief for 4th edition
Guideline of Ocean Observations
Shigeyoshi Otosaka