News

Staff Highlights: Prof. Chengxiang ZHUGE

The development of smart cities contributes to inclusive growth, resilience, and global sustainability efforts, and thus plays a crucial role in advancing the Sustainable Development Goals (SDGs).   Prof. Chengxiang Zhuge, Assistant Professor from the Department of Land Surveying and Geo-informatics (LSGI) is leading the TIP research group focusing on Technology innovation, Infrastructure planning and Policy making in Smart Cities. They consider cities as complex systems and develop technologies and models to address urban issues based on artificial intelligence, simulation approaches and big data analytics. Recently, they are particularly interested in the TIP-related research topics in the mobility and residential sectors.   Topic 1: Electric Vehicle User Behavior Analysis and Modelling and Infrastructure Planning Many cities are acting actively to electrify their transportation system towards a smart and sustainable mobility system. In 2024, electric vehicle (EV) sales in China surpassed 10 million units, accounting for 61% of global sales. The TIP group focuses on understanding EV user behavior and optimizing the layout and operation of charging infrastructure. From the behavioral perspective, they have developed an EV big data analytical framework based on large-scale real-world trajectory data from over 100,000 EV users. This framework can help to uncover the underlying mechanisms behind EV users’ travel, parking, and charging decisions.   To support short-term charging demand forecasting, the TIP group integrate deep learning techniques with the spatiotemporal patterns of charging demand. Their models enable accurate short-term predictions of charging needs at the station or regional level, thereby supporting more efficient infrastructure operations and management. For infrastructure deployment, the TIP group propose a series of microsimulation-based optimization models considering multiple energy sources, vehicle types, facility types, and stakeholder objectives. These models can help to search for tailored solutions that balance factors such as system cost, carbon emissions, and operational efficiency. The case studies span a range of cities, including Hong Kong, Beijing, Shenzhen, and New York.   Topic 2: Agent-based Urban Simulation Model As a typical complex system, city is composed of multiple interrelated and interdependent subsystems, including transportation, land use, energy, environment, population, and economy. Urban micro-simulation models have been increasingly used as decision support systems to explore such complex dynamic systems, enabling urban planners and policymakers to systematically evaluate the impacts of various planning strategies and policy interventions, anticipate long-term urban development patterns under different scenarios, and provide scientific evidence to support urban planning, policy making, and technology investment.   The TIP group has been developing an open-source agent-based urban simulation model, SelfSim. Compared with existing urban micro-simulation models, SelfSim is focused on simulating the impacts of sustainable technologies, policies, and infrastructures. Its modular framework allows for the integration of various low-carbon technology diffusion models and the social network evolution model. Based on open-source data, the TIP group has applied SelfSim in five global cities: Beijing, Shenzhen, London, Berlin, and New York. These city-scale scenarios allow for the simulation-based appraisal of a wide range of planning and policy strategies, offering decision support for sustainable urban development.   Topic 3: Adoption and Impacts of Low-Carbon Technologies and Services In 2019, the buildings and transport sectors each accounted for 29% of global end-use energy consumption and contributed 19% and 7%, respectively, to direct energy-related greenhouse gas (GHG) emissions. Studies indicate that by 2050, demand-side measures could reduce GHG emissions from buildings and land transport by 66% and 67%, respectively.   The TIP group focuses on the adoption behaviors of low-carbon technologies and services within the transportation and residential sectors. Using urban big data analytics and agent-based simulation methods, the group investigates the mechanisms behind the interlinked adoption of emerging technologies and services, particularly within development of smart cities. These include autonomous vehicles, shared mobility, and new energy vehicles in the transport sector, as well as smart home technologies, smart heating/cooling systems, and energy-efficient lighting systems in the residential sector. Based on the empirical analysis and simulation modeling of adoption behaviors, the TIP group has further developed an integrated framework to assess their impacts from infrastructural, energy, environmental, and social perspectives.

PolyU 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 researchprovides 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-informatics and 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 Chensaid, “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.” More information can be found in the Media Release (PolyU research reveals sharp depletion in soil moisture, driving land water to flow into the oceans and contributing to a rise in sea levels) of PolyU.

LSGI Hosts RICS Accreditation Visit

On 27 March 2025, the Department of Land Surveying and Geo-Informatics (LSGI) welcomed a visit from the Royal Institution of Chartered Surveyors (RICS) for an Accreditation and Reaccreditation review. This visit reflects LSGI’s ongoing efforts to maintain quality education and industry relevance. During the one-day visit, the RICS team toured LSGI’s facilities, including various laboratories and survey equipment store, to understand the resources available for research and teaching. The team also attended a presentation on the unique aspects of LSGI’s programmes, highlighting the department's focus on providing up-to-date education in land surveying and geo-informatics. The visit featured engaging meetings with LSGI staff, students, and industry representatives, offering insights into the collaboration between academia and industry to ensure programmes meet professional standards. The RICS visit underscores LSGI's dedication to high educational standards and strong industry ties. LSGI looks forward to continuing its partnership with RICS to enhance its programmes. For more information about LSGI’s programmes and initiatives, please visit https://www.polyu.edu.hk/lsgi/study/.

Staff Highlights: Prof. Quoqiang Shi

Urbanization brings rapid development but also exacerbates geological and environmental risk, such as land subsidence, infrastructure instability, and landslides. These challenges threaten the safety of millions and demand advanced monitoring solutions. Prof. Guoqiang Shi and his team work on urban remote sensing, leveraging Interferometric Synthetic Aperture Radar (InSAR) to monitor and analyse urban geological vulnerabilities from underground, ground surface, to the built upper ground. By integrating InSAR remote sensing, big data analytics and artificial intelligence (AI), the team aims to provide critical insights for urban resilience, infrastructure maintenance, and sustainable development.   Topic 1: Uneven Settlement in Coastal Reclamations Reclaimed areas, common in land-scarce cities like Hong Kong, are prone to uneven settlement due to soft subsurface layers. Constrained by its steep terrain, Hong Kong has over 25% of its developable land reclaimed from the sea. Using spaceborne InSAR, we detected rapid subsidence at Hong Kong International Airport’s Third Runway, a major reclaimed project. Our high-resolution data revealed soil compression patterns and fill-layer dynamics, offering engineers and policymakers actionable insights for soil reinforcement, infrastructure planning, and future reclamation projects (e.g., the ‘Lantau Tomorrow Vision’). This work underscores the need for continuous monitoring in reclaimed zones to prevent long-term risks.   Topic 2: Groundwater and Urban Land Subsidence Unlike the artificial foundations in Hong Kong, the Yangtze River Delta (YRD) has vast and flat areas of natural sediments. Excessive groundwater extraction has caused severe subsidence in cities like Suzhou, where some areas sank over 2 meters before extraction was banned in 1997. Using InSAR, we quantified the slowdown in subsidence post-ban, demonstrating the policy’s effectiveness. However, traditional geological and surveying methods failed to evaluate the groundwater policy on a city-wide scale. Figure 2 illustrates the post-ban recovery (slowing) of Suzhou’s land subsidence, as captured by satellite InSAR. These findings are vital for groundwater management in vulnerable regions (e.g., the North China Plain), supporting sustainable urban planning and resource policies.   Topic 3: Infrastructure Health and Slope Safety Beyond subsurface risks, InSAR enables large-scale structural and slope safety monitoring. In Hong Kong, we applied it to assess highway stability and generate 3D building point clouds, identifying high-risk structures. Risky slopes/landslides adjacent to buildings/transportations can be surveillance timely and located for accurate mitigation and evacuation planning. As satellite data improves, InSAR is becoming indispensable for smart city platforms, offering precise, real-time diagnostics for next-generation urban resilience solutions.   Photo 2: Reclamation subsidence and soil consolidation of the HKIA 3rd RunwayPhoto 3 & 4: Urban land subsidence recovery in Suzhou City following the implementation of groundwater extractionPhoto 5: InSAR 4D data for infrastructure and slope safety assessment   Welcome to join Prof. Shi’s team! Prof. Shi and his team are advancing InSAR algorithms for complex urban terrains and developing AI-driven models to mine geohazard data. They welcome students from diverse academic backgrounds to join LSGI and join our group. For contact details, please refer to the information below. They are looking forward to collaborating with you!   Personal web: https://guoqiangshi.github.io/ LSGI web: https://www.polyu.edu.hk/lsgi/people/academic-staff/ Email: guoqiang.shi@polyu.edu.hk   References: Jiang Z, Shi G, Wu S, et al. Unveiling multimodal consolidation process of the newly reclaimed HKIA 3rd runway from satellite SAR interferometry, ICA analytics and Terzaghi consolidation theory. Remote Sensing of Environment, 2025, 318: 114561. https://doi.org/10.1016/j.rse.2024.114561 Shi G, Huang B, Leung A K, et al. Millimeter slope ratcheting from multitemporal SAR interferometry with a correction of coastal tropospheric delay: a case study in Hong Kong. Remote Sensing of Environment, 2022, 280: 113148. https://doi.org/10.1016/j.rse.2022.113148 Shi G, Ma P, Hu X, et al. Surface response and subsurface features during the restriction of groundwater exploitation in Suzhou (China) inferred from decadal SAR interferometry. Remote Sensing of Environment, 2021, 256: 112327. https://doi.org/10.1016/j.rse.2021.112327 Shi G, Lin H, Bürgmann R, et al. Early soil consolidation from magnetic extensometers and full resolution SAR interferometry over highly decorrelated reclaimed lands. Remote Sensing of Environment, 2019, 231: 111231. https://doi.org/10.1016/j.rse.2019.111231 Shi G, Lin H, Ma P. A hybrid method for stability monitoring in low-coherence urban regions using persistent and distributed scatterers. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2018, 11(10): 3811-3821. https://doi.org/10.1109/JSTARS.2018.2867832      

Prof. Yang Xu Honored with Outstanding Alumni Award from University of Tennessee, Knoxville

Prof. Yang Xu, Associate Head of Partnership and Associate Professor, has been awarded the prestigious Outstanding Alumni Award by the Department of Geography and Sustainability at the University of Tennessee, Knoxville. This accolade celebrates Prof. Xu's remarkable mid-career achievements and his significant contributions to the field of Geographic Information Science. University of Tennessee, Knoxville (UTK) is a public land-grant research university in the United States. The university is also classified among "R1: Doctoral Universities – Very high research activity" according to the Carnegie Classification of Institutions of Higher Education. This classification highlights the university's emphasis on research excellence and its role in promoting the academic and professional growth of its alumni. Congratulations to Prof. Xu!

LSGI Alumni Appointed as Tenure-Track Assistant Professor at Nanjing University

Dr. Jiaqi Tian, a former Ph.D. graduate from the Department of Land Surveying and Geo-Informatics (LSGI) at the Hong Kong Polytechnic University (PolyU), has been appointed as a tenure-track assistant professor at the International Institute of Earth System Science (ESSI) at Nanjing University. Under the mentorship of Professor Xiaolin Zhu and through his work at the PRIDE (PolyU Remote Sensing Intelligence for Dynamic Earth) Lab, Dr. Tian earned his Ph.D. in 2021 and developed his expertise and research capabilities in his field. ESSI is a leading academic institution in the fields of quantitative remote sensing and terrestrial carbon cycle research. LSGI is honoured by his career milestone.   Congratulations to Dr. Tian on this well-deserved achievement!   Dr Jiaqi Tian’s Personal Web Page: https://scholar.google.com/citations?user=RNCJZEYAAAAJ&hl=en PRIDE Lab: https://xzhu-lab.github.io/

PolyU Achieves Prestigious Global Rankings in Geography and Remote Sensing

The Hong Kong Polytechnic University (PolyU) has achieved impressive global rankings, highlighting its academic excellence. PolyU's Geography programme is ranked 37th in the QS World University Rankings by Subject 2025, and its overall QS ranking has risen to 57th in 2025. The Remote Sensing discipline has also advanced significantly, moving from 38th in 2023 to 15th in the ShanghaiRanking's Global Ranking of Academic Subjects 2024. These accomplishments reflect the Department of Land Surveying and Geo-Informatics (LSGI)’s commitment to excellence in academics, research, and industry partnerships, showcasing our dedication to advancing knowledge in Geography and Remote Sensing. PolyU's achievements affirm its status as a leading institution in the Asia-Pacific region and beyond. By fostering innovation and collaboration, the university attracts top talent and forms strategic partnerships, enhancing its academic and research strengths. LSGI is proud of its contributions to these successes. For more details, you can visit the QS University Subject Rankings for Geography and the ShanghaiRanking's Global Ranking of Academic Subjects 2024 for Remote Sensing.

Feature Talk "Seeing and Unseen Underground Utilities in 3D" at Geospatial Lab

On 22 February 2025, Ir. Prof. Wallace Lai, Associate Head of Department (Teaching) was invited to be the guest speaker for a feature talk "Seeing and Unseen Underground Utilities in 3D" at the Geospatial Lab. The talk attracted 23 participants who attended in person and 30 people participated online. We sincerely thank all participants for their enthusiastic engagement and the support from Geospatial Lab. This presentation explored the intricacies of Hong Kong's underground pipelines, highlighting methods to accurately locate them without excavation. During the interactive session, participants also discovered detection technologies, gaining valuable insights into the measurement and data analysis of the underground world. Click here to read more.

LSGI Joint Research with International Scientists Unveils Ice Sheet Melt Behavior in Greenland Using Satellite Positioning Data

We are thrilled to share that Prof. Jianli CHEN, Professor of the Department of Land Surveying and Geo-informatics (LSGI) together with a team of global researchers, have integrated various modern space geodetic techniques, particularly satellite positioning data, to monitor the subsidence of vertical bedrock and successfully quantify summer water storage in the Greenland ice sheet. This groundbreaking research, published in the prestigious journal Nature, offers new insights and evidence regarding the contribution of ice sheets to global sea-level rise. The Greenland ice sheet, second only to Antarctica in size, plays a crucial role in global sea-level rise. If it were to melt completely, sea levels could rise by an alarming seven meters. Despite its significance, many aspects of how water accumulates, is stored, and is released within the ice sheet remain unclear. Prof. Jianli Chen, collaborated with experts from Hong Kong, Mainland China, the US, the Netherlands, and Belgium, has made significant strides in understanding these processes by integrating advanced satellite positioning data and other space geodetic techniques. The research team focuses on the evolution meltwater storage to gain a deeper understanding of ice sheet melting behavior and its effects on sea-level rise. They have been at the forefront of utilizing the Greenland GPS Network (GNET) and satellite gravity data from NASA’s Gravity Recovery and Climate Experiment. With nearly 22 Global Navigation Satellite System (GNSS) stations positioned around Greenland, they continuously gather positioning data. This has led them to conclude that high summer temperatures could become a regular occurrence in the future. Accurately predicting meltwater storage during these periods is essential for evaluating sea-level rise. Prof. Chen highlighted that the study, which took years of preparation, not only integrated various modern space geodetic techniques but also involved challenging expeditions to some of the most remote areas on Earth. He emphasized that the significant results highlight the importance of extensive international cooperation in addressing climate change challenges. Their research would contribute to achieving accurate model performance for warmer years, which would aid in projecting ice-sheet behavior and its impact on sea-level rise in the coming decades. This research underscores our academic staff's dedication to advancing scientific knowledge and addressing the pressing issue of climate change. Our work is vital for developing accurate models to predict future sea-level changes, particularly in light of anticipated Arctic warming.    Media coverages: 18 Feb 2025 Oriental Daily News (格陵蘭融冰機制 理大以衞星數據解謎) - https://polyu.me/4b2Bzv2 Ming Pao Daily News (理大衛星數據測格陵蘭融水) – https://polyu.me/431denw am730 (理大參與研究格陵蘭冰蓋融化 助預測海平面上升速度) - https://polyu.me/3X3Goyi Ta Kung Pao (理大參與研究格陵蘭冰蓋融化 助預測海平面上升速度) - https://polyu.me/3X17FBB Wen Wei Po (理大與國際專家靠衛星定位數據 揭示格陵蘭冰蓋融化機制)- https://polyu.me/4hGscU6 Hong Kong Commercial Daily (理大與國際專家合作運用衛星定位數據 助預測海平面上升速度) - https://polyu.me/415fWpm Dot Dot News (理大參與研究格陵蘭冰蓋融化 助預測海平面上升速度) - https://polyu.me/4hFRBgV Line Today (理大參與研究格陵蘭冰蓋融化 助預測海平面上升速度) - https://polyu.me/42Zm1WH Hong Kong China News Agency (理大參與研究格陵蘭冰蓋融化 助預測海平面上升速度) - https://polyu.me/4bbDSMj 19 Feb 2025 Wuxi Daily (理大與國際專家合作運用衛星定位數據 揭示格陵蘭冰蓋融化機制) - https://polyu.me/4gNsebR 羊城晚報 (創新採用衛星數據破解冰蓋融化國際難題 理大學者參與研究助預測海平面上升速度) - https://polyu.me/4k1P4iC 南方日報 (理大研究揭格陵蘭冰蓋融化機制 助預測海平面上升速度) - https://polyu.me/41pV6RR Sina (創新採用衛星數據破解冰蓋融化國際難題 理大學者參與研究助預測海平面上升速度) - https://polyu.me/41jxQFX Sohu (理大研究揭格陵蘭冰蓋融化機制 助預測海平面上升速度) - https://polyu.me/3X6cgT6 Zhihu (理大參與研究格陵蘭冰蓋融化 助預測海平面上升速度) - https://polyu.me/4b7ImmY  

PolyU Osaka Study Tour 2025

From 4 to 10 January 2025, a group of 24 LSGI students, led by Prof. Wallace Lai, Prof. Qing Pei, Miss Stella Tse from Department of Land Surveying and Geo-Informatics (LSGI) visited Osaka and Kyoto for a 7-day study tour supported by the university. The aim of this tour was to explore the elements of spatial data science and smart cities.    At the Osaka City Abeno Disaster Prevention Center, students engaged in practical exercises that illustrated the importance of disaster preparedness. They learned why cars should not be used during a tsunami, experienced how an Earthquake shakes the Earth in a simulator, and practiced how to 'crawl' properly amid heavy smoke. Prof. Pei-liang Xu from the Disaster Prevention Institute at Kyoto University provided valuable insights into Japan's earthquake warning system, which utilizes a sophisticated network of spatial data science and technologies, including GNSS, GIS, remote sensing, geodesy, and seismology. He emphasized the philosophical dimension of disaster research, urging students to critically question scientific claims with the challenge: "Don't trust what 'Science' or 'Nature' tells you. If you care, question it and prove it yourself." The exploration of "Disaster" extended to its man-made dimensions through discussions led by Prof. Keiji Yano, Institute of Disaster Mitigation for Urban Cultural Heritage from Ritsumeikan University, who introduced his 20 years of effort on 'Virtual Kyoto'. It aims to preserve the rich Kyoto's cultural heritage from various disasters via technologies like GIS, cartography, aerial photogrammetry, laser scanning, and AI. This initiative highlights the power of a map, which is not just a large piece of paper, but a vivid story-telling vehicle recording our past and present leading us to the future. In a world where heritage is endangered, mitigation and preservation of heritage from disaster are a serious matter of humanity and should be made known to everyone. The students were stunned at how the techs they have been learning in LSGI are so closely related to humanities and heritage conservation, traditionally perceived as separate domains.    The tour also included a visit to the Kyoto Museum for World Peace led by Prof. Keiji Yano. It is a solemn place where facets of war should be presented in a multitude of ways aimed at avoiding it. Ms. Miki Taguwa, the curator of the museum, kindly guided the students through the various peace-making exhibits.  With the assistance of Dr. Pei Qing's excellent Japanese translation, Prof. Wallace Lai was able to explain the discovery of WWII fortification and field positions in his 'Geo-project 1941' originated from the Battle of Hong Kong.    This study tour not only broadened our students' understanding of disaster mitigation but also illuminated the profound interconnectedness of science, technology, and the humanities in addressing the challenges faced by society.