Understanding Complex Landscapes and Revealing Hidden Ground Features

The project “Antiquity and Heritage Lost, Found and Revealed: Promotion of 21st Century Geo-spatial Technologies” led by Prof. Wallace Wai Lok LAI of the Department of Land Surveying and Geo-Informatics at The Hong Kong Polytechnic University aims to uncover hidden and buried wartime relics, cultural antiquities, and heritage sites across Hong Kong by utilizing advanced geospatial technologies. The LiDAR datasets were processed using Red Relief Image Mapping (RRIM), a visualization technique that reveals subtle terrain features even under dense vegetation canopies. The first dataset was acquired using a RIEGL airborne LiDAR system (ALS) flown by helicopter at approximately 2,000 to 3,000 feet, while the second dataset was captured using a RIEGL UAV sensor (ULS) flown at around 90 meters above ground level on a drone. 

Despite the substantial differences in acquisition altitude and platform, both datasets successfully revealed the underlying terrain morphology. The comparison highlights the complementary strengths of ALS and ULS approaches: airborne LiDAR provides efficient, large‑area coverage, while UAV‑based LiDAR delivers high‑resolution detail and operational flexibility for targeted project areas. 

The airborne dataset originates from a territory-wide LiDAR capture conducted with a RIEGL VQ‑1560i system (a predecessor of the RIEGL VQ-1560 III-S), already demonstrating strong vegetation penetration capabilities. Building on this foundation, the team acquired more detailed UAV datasets using the RIEGL VUX‑120²³, further enhancing terrain detail at a finer spatial resolution. Together, these datasets show how combining ALS and ULS can provide a more complete understanding of complex landscapes and reveal ground features invisible in conventional aerial imagery.

With the high-resolution dataset captured by the VUX-120²³, the team directly assessed differences in terrain representation, clarity, and level of detail. According to Prof. Wallace LAI, the results clearly demonstrate how LiDAR, as a cutting-edge technology, can capture ground terrain in ways that no other capture method can match, helping to uncover and preserve cultural legacies.

Expanding the Reach: The Melaka Project

This work also forms part of a broader research trajectory. Following the successful identification of wartime pillboxes, hidden tunnels, and other historical structures in Hong Kong, Prof. Wallace Lai’s team applied similar approaches of using state-of-the-art geospatial technologies to heritage research in Malaysia. This included a project in the historic region of Melaka (formerly Malacca), a UNESCO World Heritage city. These subsequent efforts build on experience gained from utilizing airborne and UAV LiDAR data to identify areas of interest, followed by detailed documentation using the RIEGL VZ-600i Terrestrial Laser Scanner. The results demonstrate how RIEGL technology supports both methodological evaluation and real‑world heritage applications across Southeast Asia. 

The Melaka project further illustrates how advanced geospatial technologies can support heritage research by revealing historical features that would otherwise remain hidden. By integrating laser scanning, historical records, and geophysical techniques, researchers can reconstruct lost landscapes and provide new perspectives on cultural heritage. 

As the study expands to additional regions in Malaysia, Indonesia, and the United Kingdom, the work led by Prof. Wallace Wai-Lok LAI underscores the growing importance of modern geospatial technologies in heritage discovery, documentation, and education across Southeast Asia. 

In collaboration with GPS Lands Malaysia, RIEGL’s local distribution partner, the PolyU team produced a documentary at the Melaka project showcasing how cartography, maps, and modern laser scanning technologies are integrated into a broader framework of geospatial education and public engagement.

Watch their YouTube video and explore how geo-spatial science brings Malacca history back to life!

From wide area aerial data capture to documenting every brick and column of the historical building, RIEGL systems empower researchers, surveyors, and historians to tailor data acquisition strategies to their needs – revealing what would otherwise remain hidden and forgotten beneath the canopy. 

About the Department of LSGI at The Hong Kong Polytechnic University

Established in 1982, the Department of Land Surveying and Geo-Informatics (LSGI) at The Hong Kong Polytechnic University (PolyU) is the only academic unit in Hong Kong providing comprehensive education and research in geomatics, land surveying, and GIS. Focusing on smart cities and spatial data, it offers accredited undergraduate and postgraduate programs, preparing professionals for surveying, mapping, and urban informatics careers.

The department is known for its applied research that addresses real-world industrial and community needs. Key research areas and facilities include: 

• Space & Space Exploration:
  LSGI scholars contribute to national space missions, including planetary mapping and aerospace technology innovation.
• Smart Cities & AI:
  The Laboratory for Smart City and Spatial Data Analytics uses VR/AR and big data to develop solutions for urban challenges.
• Underground Utilities:
  Specialized research into non-invasive technologies for inspecting and managing underground infrastructure and heritage sites.
• Environmental Monitoring:
  Research on global climate issues, such as the impact of Arctic wildfires on snow cover and studies on the Earth's rotational axis (Chandler wobble). 

LSGI currently uses RIEGL terrestrial, UAV-based, and mobile laser scanning equipment.

RIEGL Asia Pacific is also proud to have contributed to the university’s first LiDAR course through a “guest lecture” and the use of RIEGL training modules.

www.polyu.edu.hk/lsgi/