News

RILS researchers use novel satellite laser ranging technique to reveal accelerated global average sea-level rise with 90 mm surge over past 30 years

The rise in global mean sea level (GMSL) is a critical indicator of climate change. The Hong Kong Polytechnic University (PolyU) researchers have utilised advanced space geodetic technologies to deliver the first precise 30-year (1993-2022) record of global ocean mass change (also known as barystatic sea level), revealing its dominant role in driving GMSL rise. Their research further indicates that GMSL has been increasing at an average rate of approximately 3.3 mm per year with a notable acceleration observed, highlighting the growing severity of climate change. The research findings have been published in the Proceedings of the National Academy of Sciences. GMSL is primarily driven by two factors: the thermal expansion of seawater — as the oceans absorb around 90% of the excess heat in the Earth’s climate system — and the increase in global ocean mass, which is mainly caused by the influx of freshwater from melting land ice. Therefore, long-term monitoring of global ocean mass change is essential for understanding present-day GMSL rise. A research team led by Prof. Jianli CHEN, Chair Professor of Space Geodesy and Earth Sciences of the PolyU Department of Land Surveying and Geo-Informatics (LSGI) and a core member of the PolyU Research Institute for Land and Space, together with Dr Yufeng NIE, Research Assistant Professor of LSGI and the lead and corresponding author of the research, has, for the first time, provided direct observations of global ocean mass estimates between 1993 and 2022 by utilising time-variable gravity field data derived from satellite laser ranging (SLR). In the past, scientists have relied on long-term observations from satellite altimetry to project sea-level rise. Barystatic sea level records based on satellite gravimetry only became available with the launch of the Gravity Recovery and Climate Experiment in 2002. SLR is a traditional space geodetic technique used to accurately measure the distance between satellites and ground stations via laser ranging. However, fundamental constraints of SLR, such as the limited number of satellites and ground stations, the high altitude of the satellites (which means SLR-derived gravitational changes capture only the longest wavelengths) and the low-degree gravitational measurements, have restricted its direct application in estimating ocean mass change. To effectively utilise SLR-derived gravitational fields for accurate estimates of ocean mass change, the research team implemented an innovative forward modelling technique that tackles spatial resolution limitations by incorporating detailed geographic information of ocean-land boundaries. This approach enables long-term monitoring of global ocean mass changes. The research revealed that an increased rate of GMSL resulted in a global average sea-level rise of approximately 90 mm between 1993 and 2022, with about 60% of this rise attributable to ocean mass increase. Since around 2005,  the rise in GMSL has been primarily driven by the rapid increase in global ocean mass. This overall increase is largely driven by the accelerated melting of land ice, particularly in Greenland. Throughout the entire study period, land ice melt from polar ice sheets and mountain glaciers accounted for over 80% of the total increase in global ocean mass. Prof. Jianli CHEN said, “In recent decades, climate warming has led to accelerated land ice loss, which has played an increasingly dominant role in driving global sea-level rise. Our research enables the direct quantification of global ocean mass increase and provides a comprehensive assessment of its long-term impact on sea-level budget. This offers crucial data for validating coupled climate models used to project future sea-level rise scenarios.” Dr Yufeng NIE said, “The research showed that the ocean mass changes derived from SLR analysis align well with the total sea level changes observed by satellite altimeters, after accounting for the effect of ocean thermal expansion. This demonstrates that the traditional SLR technique can now serve as a novel and powerful tool for long-term climate change studies.”

Prof. WENG Qihao publishes comment article on urban visual-spatial intelligence

Prof. WENG Qihao, Associate Director of the Research Institute for Land and Space (RILS), Director of the Research Centre for Artificial Intelligence in Geomatics (RCAIG), Chair Professor of Geomatics and Artificial Intelligence and Global STEM Scholar in the Department of Land Surveying and Geo-Informatics, together with his research team has recently published an article titled “Urban visual-spatial intelligence: linking human and sensor perception for sustainable urban development” in npj Urban Sustainability.   The article points out that UVSI integrates human perception with advanced sensor technologies, moving beyond traditional smart city models that prioritise technology alone. By combining data from sources such as satellite imagery, IoT sensors, mobile devices, and social media, UVSI provides a real-time, multi-dimensional understanding of urban environments.   A central feature of UVSI is its collaborative framework, ensuring continuous feedback between residents, technology, and urban spaces. This adaptive approach supports dynamic urban management and aligns with the United Nations Sustainable Development Goals, particularly SDG 11 for sustainable cities. UVSI informs policy-making, infrastructure planning, disaster monitoring, and climate action, while upholding privacy and public trust.   Nonetheless, challenges persist, especially the integration of diverse types of data across geographical contexts and addressing associated biases. The research team believes that future research will focus on open-source models, digital twins, and ethical, AI-driven urban planning.   As cities expand, UVSI’s holistic method promises more resilient, inclusive, and liveable urban environments by bridging technology and human experience, ensuring urban development remains responsive to the needs of all communities.   Read the full paper: https://www.nature.com/articles/s42949-025-00256-2

Ir LAM Sai-hung, IAC Chairman of RILS, honoured as Justice of the Peace

We are pleased to announce that Ir LAM Sai-hung, the International Advisory Committee (IAC) Chairman of RILS and former Secretary for Transport and Logistics, has been appointed as a Justice of the Peace (JP) with effect from 1 July 2025. This prestigious appointment recognises Ir Lam's exceptional contributions to public service and his distinguished career in transportation and logistics. In his new role, Ir Lam will continue to play a vital part in shaping the future of RILS, working closely with IAC members to advance research and development in land and space. His expertise and leadership will remain invaluable to the RILS community, and we look forward to his continued collaboration and guidance in driving innovation and excellence in our research endeavors.

RILS Public Lecture was successfully held at PolyU on 11 June 2025

The RILS Public Lecture, held on 11 June 2025 at The Hong Kong Polytechnic University (PolyU), featured Prof. Yan LIU, Professor of Geographical Information Science at Department of Geography and Resource Management, The Chinese University of Hong Kong, who delivered an enlightening talk on "Advancing Computational and Spatial Social Sciences in the Era of Big Data: Opportunities and Challenges". The lecture was chaired by Prof. Qihao WENG, Associate Director of RILS, Director of RCAIG and Chair Professor of Geomatics and Artificial Intelligence. This successful event was jointly organised by the Research Institute for Land and Space (RILS), Department of Land Surveying and Geo-Informatics (LSGI), Research Centre for Artificial Intelligence in Geomatics (RCAIG), China Harbour – PolyU Joint Research Centre for Land Development, and PolyU-Yangjiang Laboratory Joint Research Centre for Offshore Wind Power of PolyU. Prof. LIU drew on her research at the University of Queensland to showcase the diverse applications of spatial data and analytical models in unveiling urban and social changes, including modelling urban growth, human social interactions, public transport policies, and population health. She also discussed contemporary issues and challenges in spatial social science research, such as data security, privacy and accessibility, and highlighted the need for new methodologies, including AI and machine learning, to handle big data sources. The lecture concluded with Prof. LIU sharing her thoughts on future opportunities in the emerging field of Computational and Spatial Social Sciences, inspiring attendees to explore the vast potential of this interdisciplinary field.

RILS study revealing Malacca heritage with cutting-edge geospatial technologies

A project named “Antiquity and Heritage Lost, Found and Revealed: Promotion of 21st Century Geo-spatial Technologies” led by Prof. Wallace LAI Wai-lok, Member of the Research Institute for Land and Space (RILS), Associate Head (Teaching) and Professor of the Department of Land Surveying and Geo-informatics, has been granted HK$3.22 million from the General Support Programme under the Innovation and Technology Fund (ITF-GSP) of the Innovation and Technology Commission of the HKSAR Government. This two-year project, in collaboration with the Hong Kong Baptist University and local amateur war historians, aims to uncover and document the city’s concealed historical sites using advanced geospatial technologies. By employing techniques such as geo-referencing, airborne and terrestrial laser scanning, and geophysical technologies, the team is capturing detailed images of buried wartime relics and antiquities, bringing these lost historical relics back to light. To foster community involvement in STEAM (science, technology, engineering, arts, and mathematics) education, the team will organise public programmes such as guided visits to cultural and wartime heritage sites, STEAM-focused seminars, interactive workshops, and immersive exhibitions. The team has collaborated with wide stakeholders including government bodies, universities and industry partners, science magazines, non-government organisations and local village community to enhance public engagement and advance the application of geospatial innovations in uncovering Hong Kong’s hidden historical stories. In May 2025, the team expanded the study scope to Malacca, Malaysia, where they conducted 3D scanning and mapping of historic structures, including the Porta de Santiago and St. Paul’s Church. By integrating digitised historical maps with modern scanning technologies, the team identified remnants of long-buried colonial fortifications. Further expeditions to other regions in Malaysia and Indonesia are planned.   Press release: https://www.polyu.edu.hk/tc/media/media-releases/2025/0604_polyu-study-uncovering-hong-kong-s-hidden-history-with-cutting-edge-geospatial-technologies/ Online coverage: HK01 - https://polyu.me/4mNd5LL Bastille Post - https://polyu.me/4ktud7O Dot Dot News - https://polyu.me/4ksFCEP hkong.hk- https://polyu.me/4kR8y9a Hong Kong Economic Times - https://polyu.me/45eqdTL (subscription required) Bauhinia - https://polyu.me/43Jt84w

RILS co-organised The Third ACOWS Workshop at PolyU

The third Workshop on Atmospheric and Coastal Observations for Weather Servicing (ACOWS 2024) was hosted by Prof. George LIU, Professor at the Department of Land Surveying & Geo-Informatics (LSGI) and member of Research Institute for Land and Space (RILS), at The Hong Kong Polytechnic University (PolyU) during 2-3 April 2025. This year’s theme, “Data Assimilation for a Better Weather Forecasting”, brought together experts to explore cutting-edge advancements in weather prediction methodologies. Renowned scientists from Mainland China were invited to attend this Workshop and present their work. They are Prof. Jianhua SUN from the Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing; Prof. Yaodeng CHEN from the School of Atmospheric Sciences, Nanjing University of Information Science and Technology; Dr Yerong FENG, Director, from the Guangdong–Hong Kong–Macao Greater Bay Area Weather Research Centre for Monitoring Warning and Forecasting, Shenzhen; Dr Yuanfu XIE, Chief Scientist, from the Guangdong–Hong Kong–Macao Greater Bay Area Weather Research Center for Monitoring Warning and Forecasting, Shenzhen; Prof. Donghai WANG from the School of Atmospheric Sciences, Sun Yat-sen University; and Dr Chunqing SHANG, the Huawei Technologies Company.   Presentations focused on innovative approaches to “Forecasting of Heavy Rainfall using multi-source PWV data assimilation and ensemble prediction”, a work package being led by Prof LIU. Discussions highlighted the integration of multi-source data to enhance predictive accuracy and address climate resilience challenges. The Workshop fostered interdisciplinary collaboration, bridging academic research with operational weather servicing needs.

RILS research reveals sharp depletion in soil moisture, driving land water to flow into the oceans and contributing to a rise in sea levels

The increasing frequency of once-in-a-decade agricultural and ecological drought has underscored the urgency of studying hydrological changes. A research team from the Department of Land Surveying and Geo-informatics of The Hong Kong Polytechnic University (PolyU) has collaborated with international experts to analyse the estimated changes in land water storage over the past 40 years by utilising space geodetic observation technology and global hydrological change data. This innovative method has revealeda rapid depletion in global soil moisture, resulting in a significant amount of water flowing into the oceans, leading to a rise in sea levels. The research provides new insights into the driving factors behind the alarming reduction in terrestrial water storage and rise in sea levels. The findings have been published in the international journal Science. Since polar motion reflects mass redistribution within the Earth system, integrating models and observations across the atmosphere, hydrosphere and lithosphere is crucial. However, previous challenges in measuring terrestrial water storage, particularly groundwater and root zone soil moisture, limited understanding of hydrological depletion at continental scales. Prof. Jianli CHEN, Professor of the PolyU Department of Land Surveying and Geo-informaticsand core member of the Research Institute for Land and Space and the international team employed satellite altimetry and gravity missions, including the Gravity Recovery and Satellite Experiment (GRACE), and GRACE Follow-On, to enable continental-scale observations of terrestrial water storage variations. By integrating this with global mean sea levels and polar motion data, the team has explored terrestrial water storage depletion patterns. Notably, this study introduced novel methods for estimating global soil moisture, which improves the accuracy of continental and global scale modeling to enable a more effective understanding of soil moisture variations under climate change. The melting of Greenland’s ice sheet is recognised as the largest single contributor to the rise in global sea levels, adding approximately 0.8mm annually. This study reveals that between 2000 and 2002, the global terrestrial water storage significantly declined, with a total of 1,614 billion tons of water lost to the oceans, which is twice as much as resulting from the current melting of Greenland ice, and equivalent to a 4.5mm rise in sea levels. Since then, the rapid loss of terrestrial water storage has been followed by a more gradual but continuous depletion, with no signs of recovery. In addition, compared to the period from 1979 to 1999, a notable decline in global average soil moisture was observed from 2003 to 2021. Between 2003 and 2011, the Earth’s pole shifted 58cm toward 93° East Longitude, demonstrating that the continued decline in soil moisture is leading to a reduction in terrestrial water storage. The team also pointed out that precipitation deficits and stable evapotranspiration caused by global warming, changing rainfall patterns and increasing ocean temperaturesare likely the key factors for the abrupt decline in terrestrial water storage. The ERA5-Land soil moisture data of the European Centre for Medium-Range Weather Forecasts’ corroborates these findings, showing substantial terrestrial water storage losses in Africa, Asia, Europe, and South America. In Asia and Europe, the affected areas expanded from northeastern Asia and eastern Europe to broader regions across East and Central Asia, as well as Central Europe, following the sharp water storage depletion observed between 2000 and 2002. With increasing agricultural irrigation in regionssuch as northeast China and the western United States, and global greening, soil moisture may further diminish in semi-arid areas with intensive agriculture and high levels of greening. The team suggests the need for improved land surface models which consider these factors for a more comprehensive understanding of long- term changes in terrestrial water storage. Prof. Jianli CHEN said, “Sea level change and Earth rotation serve as indicatorsof large-scale mass changes in the Earth system. Accurately measured sea level change and variation in Earth rotation provide a unique tool for monitoring large-scale mass changes in the global water cycle. By integrating multiple modern space geodetic observations, it enables comprehensive analysis of the driving factors behind changes in terrestrial water storage and sea level rise. This, in turn, provides reliable data for climate and Earth system science experts to further investigate drought issues, aiding authorities in formulating water resource management and climate change mitigation strategies to address new challenges posed by climate change.”

RILS co-organises workshop on sustainable urban development and ecological conservation

The Hong Kong Polytechnic University (PolyU) and China Innovative Urban-Rural Governance Research Network (CIURG) co-hosted a workshop under the theme of Sustainable Urban Development and Ecological Conservation on 2 April 2025.  The workshop took place in the Mai Po Nature Reserve, a wetland listed as a “Ramsar site” for its international importance. Located in Yuen Long, the Mai Po Nature Reserve is hailed as paradise for migratory birds, providing diverse habitats such as gei wai, mangroves, intertidal mudflats, reedbeds and many more to local wildlife species including waterbirds, aquatic fauna and insects.  The sanctuary is facing ecological challenges as the Northern Metropolis project includes filling fish ponds and removing woodland in the Reserve to construct part of the San Tin Technopole, a new hub for clustered innovation and technology development. Against this background, the workshop brought together 31 leaders and representatives across different sectors and institutions, including universities, government bodies and non-governmental organisations, to explore actionable strategies for nature conservation for sustainable development.  The activity was co-organised by several PolyU units, including the Research Institute for Land and Space (RILS), the Research Centre for Nature-based Urban Infrastructure Solutions (RNUS), the Research Institute for Sustainable Urban Development (RISUD), and the Department of Civil and Environmental Engineering (CEE), together with CIURG. It included technical sessions and guided tour around the Reserve.  The technical sessions, chaired by Prof. DING Xiaoli, Director of RILS, and Prof. WANG Yuhong, Director of RNUS, covered multiple topics related to the workshop theme.  These included: the Northern Metropolis development plan; digital tourism; the plan, development, and protection of Hengshui Lake National Nature Reserve; sustainable blue economy; wildlife and plants conservation; and nature-based solutions in urban design. Other guest speakers included: Ms LEUNG Kar Yee, Carrie, Chief Engineer of North Development Office at the Civil Engineering and Development Department, HKSAR; Mr SU Wansheng, Chief Executive Officer of Fujian Ticket Payment Information Technology Co., Ltd.; Mr LIU Guangning, Director of Hengshui Lake National Nature Reserve; Ms Martin KATE, Consultant at Financing Marine Conservation; Ms. Camilla ZANZANAINI, Founder and Chief Executive Officer of Nature Makers Lab; Mr David STANTON, Executive Director of Ecology and Biodiversity-Hong Kong, Aurecon; Prof. CHEN Hongyue, Professor of South China Agricultural University; Prof. LUO Chunling, Professor of Guangzhou Institute of Geochemistry, Chinese Academy of Sciences; Prof. DENG Xiaomei, Associate Professor at Tsinghua University; Dr. NAZEER Majid, Research Assistant Professor at PolyU; Prof. HUANG Shuping, Associate Professor at Fujian University of Technology.  Participants had fruitful discussions and were guided through various natural habitats during the tour, enjoying an immersive experience in nature and rethinking the human-nature relationship. This workshop is funded by the Public Policy Research Funding Scheme of the Chief Executive’s Policy Unit, HKSAR.  RILS would like to thank all parties including participants, the World Wildlife Fund Hong Kong (WWF HK) and sponsor, for supporting this meaningful event.  

RILS cohosts thematic seminar on hydrographic survey

The Research Institute for Land and Space (RILS) of The Hong Kong Polytechnic University (PolyU), together with the Hong Kong Institute of Surveyors (HKIS) and the Royal Institution of Chartered Surveyors (RICS), under the support of the Civil Engineering and Development Department (CEDD), has previously launched “The New Era of Hydrographic Survey”, a dedicated event series aimed at providing engineering professionals across universities, government bodies and industry with comprehensive insights into the latest advancements in the hydrographic surveying technology of CEDD, particularly the new survey vessel “Port Works 5” (PW5) of the department.   The second event of the series, a Joint Continuing Professional Development (CPD) Seminar on the theme, was successfully held on 26 March 2025, and was attended by over 100 participants.   Prof. DING Xiaoli, Director of RILS, opened by seminar by extending a warm welcome to all participants and highlighting the growing importance of hydrographic surveying in marine infrastructure development and climate resilience as well as the critical role of interdisciplinary collaboration and innovation in advancing geospatial science.   The seminar featured presentations by representatives from several HKSAR government departments.  Speakers included: Sr CHEUK Yuet Wai, Tim, Assistant Hydrographer of the Marine Department; Sr CHENG Tsz-yan, Tess, Land Surveyor of the Lands Department; and Sr LEUNG Ching-hung, Cherry, Land Surveyor of CEDD.  Their sharing covered multiple areas related to PW5 and hydrographic survey services, including the design features that enable the vessel to operate in diverse marine environments and support a wide range of survey missions, the challenges faced during the construction of PW5, and the need for adaptability, innovation and continuous professional development in the field to meet evolving engineering and surveying industry demands.   A panel discussion, moderated by Dr KWAN Shun-hang, Julian, Assistant Director (Technical) of CEDD, followed, spurring conversation among participants on the challenges and opportunities in hydrographic survey.  All members had a fruitful exchange of views, acknowledging the importance of capacity-building in the field through cross-sectoral knowledge sharing and collaboration, thus contributing professional expertise to Hong Kong’s smart and sustainable city development.

Associate Director of RILS shares research on floating solutions at Consul General Talk

The 6th Consul General Talk organised by the Policy Research Centre for Innovation and Technology (PReCIT) and supported by the Faculty of Applied Social Sciences, Global Engagement Office and Research Institute for Land and Space (RILS) of PolyU, successfully concluded on 25 March 2025 on campus. The talk featured Mr Maurits TER KUILE, Consul General of the Kingdom of the Netherlands to Hong Kong and Macau, who shared his experiences and insights in Dutch diplomacy. The Netherlands is a pioneer in developing floating solutions, presenting an exemplary model of new generation water-based architecture and public space. Taking this opportunity, Prof. Xiao Lin ZHAO, Associate Director of RILS, presented some examples of floating structures in the Netherlands, the vision of floating cities and research at RILS in this exciting field.