Guy Van Rentergem offers a fascinating behind-the-scenes look at the 3D scanning of Borneo’s legendary caves – with valuable insights and techniques that others in the field can learn from. Guy is a dedicated caver who specialises in cave surveying and scientific research. He also runs his own small business, GVR 3D TECH, focusing on bathymetric surveying in GPS-denied environments, as well as T-Lidar scanning and visualisation of caves and other structures.
Connect with Guy on LinkedIn.
Niah National Park – The Famous Caves
We have returned from a successful 3D scanning campaign of the two main caves in Niah National Park in Sarawak, Malaysia: Niah Great Cave and Painted Cave.
Niah Great Cave is renowned for the discovery of a 38,000-year-old human skull in 1958, as well as for the spectacular harvesting of edible swiftlet nests.
Editor’s note: If you’re like me, you’re probably saying, “What?! An edible nest?? Did I read that right?” Well yes, actually — these nests are made of solidified saliva, which is the main ingredient in bird’s nest soup, a delicacy of Chinese cuisine. My amazement continues…but on to the scanning!
Painted Cave boasts stunning rock art and boat-shaped coffins, which are over 2,000 years old.
Both caves are open to visitors.
Top view of Painted Cave. The point cloud has been rendered with ambient occlusion. The part in red is where the rock art and boat-shaped coffins are located.
A Legacy of Exploration: Wilford’s 1964 Cave Maps
The existing cave maps, which are still in use today, were published in the 1964 book The Geology of Sarawak and Sabah Caves by Gerald Edward Wilford. Wilford was an active field geologist who worked for the Geological Survey Department of Malaysia. These maps were drawn mainly using compass-pace and compass-tape traverses. The height of the cave passages was estimated. I can only marvel at the work that was done. These caves were surveyed at a time when Borneo was still known as the “Green Hell.” The equipment was also not up to modern standards and must have been cumbersome and heavy. Nowadays, visitors park their air-conditioned cars at the visitor center, stroll along a comfortable boardwalk for an hour, and then enter the caves. Not these guys though — respect!
Our Mission: High-Resolution Base Models for Science and Management
Our scanning project aimed to create detailed base models for scientific research. The park’s management also requested a simplified work map, which presents a new challenge for me.
Tools in the Field: The Faro Focus M70
During the project, we used a Faro Focus M70 scanner. While it’s not the top of the range, it is very suitable for scanning caves. This robust machine has survived many challenging trips to caves in the tropics and elsewhere.
Efficiency Underground: Balancing Resolution, Safety, and Speed
Scanning caves presents its own challenges. As caves are inherently dangerous environments, it is important to maximize the number of scans performed during a field day. This often requires compromises in resolution and scan time. With settings of 1/4 resolution and 1/2 quality, a point cloud of 43.7 million points can be captured in under two and a half minutes. On a good day, in a cave with few obstacles, this results in up to 80 new scans.
Why We Don’t Scan in Colour
To save even more time, we usually scan without colour — except when we need colour information, such as for rock art.
So why no colour?
There is no light in caves. This means we are completely dependent on the lights we bring with us. As cave photographers know, lighting a cave properly is challenging. This problem is made even harder by the need for consistent lighting across all scans — from the smallest passageways, which tend to be overexposed, to the largest halls, which often become underexposed. Also, bringing that many lights — and keeping them charged — in remote parts of the world can be difficult.
Geology in Grayscale: A Better View of Cave Structure
Colour can also camouflage geological features of interest, such as distinct rock layers and fractures. Using only grayscale and ambient occlusion rendering greatly enhances the geological structure of the 3D model.
Speed and Safety: Skipping the Reference Spheres Another time saver is that we don’t use reference spheres. This eliminates the time spent discussing where to place the next one — and the risk of venturing into dangerous areas to position them in the ideal spot. Instead, we ensure there is sufficient overlap between the scans and then carry out a cloud-to-cloud registration on the computer. The software aligns the point clouds remarkably well.
Detail of the rock art in Painted Cave scanned in colour with the Faro Scene M70.
Ready to Explore More?
Animation of Niah Great Cave Animation of the Grottes de Hotton Thanks for reading! Please subscribe below to receive more content like this from Lidar News.
