Seasonal oscillations, caused by both tectonic and non-tectonic reasons, are one of the major components recorded in the Global Navigation Satellite System （GNSS） position time series. A functional model fitting has been widely used to extract seasonal oscillations, but this method requires assuming the model representing a whole time series. In this study, we develop a seasonal adjustment method based on an existing alternative approach that does not rely on a functional model assumption. In the proposed method, an estimation of an episodic component is added to the original method to express abrupt changes in a GNSS time series due to coseismic and postseismic deformations. In a synthetic test, our method successfully extracts a seasonal component from a time series with episodic changes. In addition, we apply the method to an observed GNSS position time series with a large seasonal variation. The regressed line explains the time series better than a functional model fitting. The source code of our method is now available online. We expect it will be utilized in future studies dealing with various types of datasets and crustal deformation.

　The Japan Agency for Marine-Earth Science and Technology （JAMSTEC） has published observation data and sample information obtained by research vessels and submersibles （DARWIN; https://www.godac.jamstec.go.jp/darwin/en/）. These observation data include geophysical, meteorological, physical, and chemical oceanographic data, and have been processed and quality controlled. The marine gravity data observed by shipboard gravimeters constitute one such data set. The relative gravity measurements observed by shipboard gravimeters have been converted to absolute gravity values, and the calculated free-air gravity anomalies can be downloaded from the data site. However, the marine gravity data have only been published on a cruise-by-cruise basis, and no integrated data have been published; in addition, no previous study has integrated JAMSTEC's shipboard gravimeter data. In this study, we constructed the JAMSTEC marine gravity data set for the area around Japan by integrating previously published JAMSTEC shipboard gravimeter data from more than 700 cruises. During the process of the integration, some problems were found in the published data; to deal with these problems, we reprocessed the data to improve the accuracy and reduce the inconsistencies.

　The PIXEL （PALSAR Interferometry Consortium to Study our Evolving Land surface） research group was established in 2005, the year before the launch of ALOS/PALSAR （Daichi-1）. PIXEL has been contributing to the expansion of SAR research in Japan for 20 years through the free sharing of ALOS/PALSAR data and the sharing of data processing technique through software training sessions. The history of PIXEL and its activities are reviewed.

　Results of the experiment on retrieving spatial difference in gravity acceleration by using an iGrav superconducting gravimeter as a portable relative gravimeter are presented. In 2024, we had an opportunity of moving the iGrav （serial number 003） twice, namely from the Zao station （in Miyagi prefecture） to the Fuji station （in Yamanashi prefecture）, and then to the Asama station （in Nagano prefecture）. Absolute gravity values are known for all the three stations. The differences in absolute gravity acceleration are （236.21±0.03） mGal between Zao and Fuji and （37.95±0.10） mGal between Fuji and Asama （1 Gal＝0.01 ms^－2）. In moving the iGrav between the stations, we kept the superconducting currents generating the supporting magnetic field untouched, so that the superconducting sphere was levitated during the transport. The gravity control of the iGrav was temporarily set to Strong Feedback both before the shutdown of the system at the old station and on the startup at the new station. We calibrated instrumental sensitivity of the iGrav using the data of absolute gravity measurements made at the Fuji station. The scale factor was found to be （138.57±0.27） mGal V^－1 for Strong Feedback. Our estimates of gravity difference obtained with iGrav were （237.65±0.46） mGal between Zao and Fuji and （37.05±0.07） mGal between Fuji and Asama. These results have errors of about 1 mGal in the absolute sense and about 1–2％ in the relative sense.

　This article provides an overview of the author’s geodetic research activities since joining the Geodetic Society of Japan in 2011. The primary topics include postseismic processes, interseismic strain accumulation, slow slip events （SSEs）, earthquakes, and volcanic deformation. Highlights include the detection of Earth’s free oscillations using high-rate GNSS data following the 2011 Tohoku-Oki earthquake, and subsequent analyses of postseismic deformation due to afterslip and viscoelastic relaxation. Data-driven approaches using neural networks are also introduced. Interseismic deformation is examined through both block models and continuous strain rate fields, with applications to the Japanese archipelago. Regarding SSEs, research has focused on their spatiotemporal diversity and interactions with seismic and aseismic phenomena, particularly in the Nankai Trough, the Sagami Trough, and the Tonga Trench. The article further discusses stress changes, fluid effects, and ongoing debates on the definition of SSEs. In addition, it introduces studies on gravity-related modulation of seismicity and GNSS-based inverse modeling of volcanic inflation beneath Mt. Fuji. Throughout, the article highlights both the potential and limitations of GNSS for monitoring dynamic and long-term crustal deformation, offering a perspective on current geodetic methodologies and challenges.