Nepal is a historical and geographical marvel with a rich natural and cultural heritage. The country stands out in all aspects of natural and cultural richness, whether it is the towering Himalayas, unmatched art and architecture, or impressive ethnic and cultural diversity. This small mountain haven is blessed with astonishing and unique sites within an area of just over 147,000 sq km. Nepal holds a considerably high number of places recognized by UNESCO (United Nations Educational Scientific Cultural Organization) as ‘World Heritage Sites.’ There are ten World Heritage Sites in Nepal, seven of which are in the Kathmandu Valley.
Kathmandu Valley, an ancient cultural and administrative hub, houses hundreds if not thousands of temples, monuments, and palaces with outstanding architecture and historical importance, making it a global attraction to date. UNESCO declared the valley a World Heritage Site in 1979 under criteria iii, iv, and vi of UNESCO’s operational guidelines among nine criteria [Department of Archaeology (DoA), 2007]. The valley was listed in the UNESCO World Heritage Site as a single site comprising seven monument zones. These include three historical places of Malla kings, namely Hanuman Dhoka Durbar Square (Kathmandu), Patan Durbar Square, Bhaktapur Durbar Square, two Buddhist shrines, i.e., Boudhanath and Swayambhu Mahachaitya, and two Hindu shrines, i.e., Changunarayan and Pashupatinath. Besides, the cluster of vernacular houses, open spaces, urban landscape, and other edifices like stone waterspouts, open platforms, and traditional rest houses made the valley an epitome of historic and artistic achievements and ancient civilization.
Though there is plenty of art and architectural work within the valley which depicts the glorious history of Kathmandu, efforts in proper record keeping, data collection and management of these heritages in a digital environment have been minimal. The problem was highlighted during the reconstruction of the historic sites devastated by the 2015 earthquake in Nepal. The challenge was to reconstruct the original structures as there were no references to look at besides some good quality photos of the heritage sites for preserving the essence of these sites with proper restoration and reconstruction.
Nepal Earthquake 2015, also called the Gorkha earthquake, took nearly 9,000 lives, injured more than 22,000 people, and damaged or destroyed about 750,000 houses. Kathmandu Valley alone suffered a lot of damage. In regard to heritage and architectural sites, dozens of heritage sites were completely destroyed, and hundreds suffered significant damage.
Changunarayan Temple, the oldest temple in Kathmandu Valley and one of seven world heritage sites in Nepal, faced the devastating effects of the earthquake. The Changunarayan temple in Changunarayan Municipality dates back to around the 5th Century—the Changunarayan Temple. The temple has great significance due to its architectural style, composition, and ambiance around the complex. As most of the monuments, temples, and structures of this area date way back, the main challenge during the reconstruction efforts of heritage after the 2015 earthquake was to preserve the physical presence, integrity, and architectural aesthetics of the structures. Recent studies show that, with the frequent earthquakes and the subsequent aftershocks, most of the historical buildings and cultural sites in Nepal, along with the ones in Changunarayan Municipality, have taken heavy amounts of damage, making the structures fragile and vulnerable over the period of time.
Nepal Flying Labs, a local innovation hub that has been working on the application of drones in disaster management and humanitarian action, was working on detailed municipal mapping activities. Based on the request from the municipality and other local stakeholders, Nepal Flying Labs designed an idea to map the heritage site in high resolution and share the data with relevant authorities to convince them about the benefits of creating a digital inventory of all these heritage sites. In the course of executing the idea, Nepal Flying Labs reached out to WeRobotics with the project idea. Thanks to Skydio, the leading U.S. drone manufacturer and technology partner at WeRobotics, Nepal Flying Labs received support to work on this concept and deliver a usable output. The plan was to use Skydio’s state-of-art autonomous drones with Skydio 3D scan technology for 3D mapping of Changunarayan Temple, which can, in turn, be used as a learning model for mapping other heritage sites.
The project involved the following major stages:
Permissions for Drone Operations
The temple is a UNESCO World Heritage site, and the involvement and interest from DoA were very crucial for the project to have all the necessary permissions secured to fly drones over a Changunarayan Temple heritage site. Nepal Flying Labs, in collaboration with the municipality, prepared a number of recommendations and support documents from relevant authorities and brought DoA on board to grant the required permissions to commence with the project. Likewise, the project team also liaised with the District Administrative Office, Bhaktapur, the Changunarayan Temple Preservation Committee and the Armed Police Force, and the local stakeholders, who were extremely cooperative in helping the field survey team carry out the project activities in a smooth manner.
Data Capture: 3D Scanning of the Temple
The project area, located in the heart of Bhaktapur, is crowded throughout the day with devotees, locals and religious visitors and tourists. So capturing crowd-free images was a great challenge for the team. To capture high-resolution images, the drone needed to fly autonomously at a low altitude and close to the structure, which caused another challenge and forced us to make extra efforts to secure the area and prioritize the safety of everyone around. Thanks to the security officials and members of the heritage committee, the team adopted high-caution procedures, completed the task within a very short time and conducted the flight operations during the time with a minimum rush around the temple.
The drone flight for the 3D Scan using Skydio took about two days after all the necessary permissions were secured. Due to cloudy weather conditions during the second half of the day, we performed a few more follow-up flights after the main scan days to ensure full coverage of the complex surfaces of the temple. With the cooperation and support of local security officials in the supervision of representatives from the Nepal Archaeological Department, we were able to accumulate complete 3D scan data. This was followed by image processing.
After the data capture was complete, the technical team began the processing phase. The team experimented with a number of different software packages. After iterative cycles using several software solutions, we concluded that for this 3D model in particular, the result produced using the Bentley processors had the best level of detail, optimisation, and refinement. It was this model, along with orthomosaics of the heritage site, that was shared with the Changunarayan Municipality and Department of Archaeology as project deliverables.
After necessary data processing and preparation of maps, and 3D models, a one-day dissemination workshop was organized at the Department of Archaeology (DoA), inviting all local stakeholders (representatives from the Municipality office, UNESCO, local heritage development trust, etc.).
This project contributed to the sustainable development goal 11.4 – Strengthening efforts to protect and safeguard the national heritage by identifying, collecting, and documenting the existing heritage site, trails, monuments, or landscapes in Changunarayan through developing a high-resolution image of the heritage site. Likewise, the collaboration between Skydio and Nepal Flying Labs aligned with Sustainable Development Goal 17, which emphasizes global partnerships for achieving the Sustainable Development Goals.
This project laid a foundation for the idea of digitally archiving heritage sites in a digital environment and accurately capturing their complex architecture and fine details. One of the major learnings from the project is that having an accurate digital database can provide a very good reference to the authorities in charge of heritage management activities while conducting any sort of upgrading or reconstruction activities. Though drones provided considerably good results, these results can be further expanded in the future through the use of technology such as LiDAR. The use of LiDAR sensors and image-based modeling and visualization makes it possible to gather highly detailed and accurate data for any geographical object. In the future, using drones with LiDAR sensors or ground-based LiDAR sensors can help further improve the accuracy of heritage models.
While working with heritages, the sentiments of the local communities need to be well understood and critically evaluated. Therefore, forming a consortium of relevant ministries, government authorities, and local stakeholders and receiving consent from relevant stakeholders for data acquisition is very crucial for heritage mapping and documentation. Besides, understanding the local culture and practices, the sensitivity of the heritage data, and the preservation of heritage sites’ integrity with regular consultation involving authorities responsible for preserving any heritage is vital in such projects.
Since 3D modeling of heritage sites is a relatively new concept, more sensitization events need to be organized in the future to make authorities understand the importance of digital data collection and maintaining a digital database using technologies like drones. This particular case of Changunarayan Temple could be an example for future reference.
Nepal Flying Labs would like to sincerely thank WeRobotics and Skydio for believing in us to be one of the grantees to the “Become a Skydio first-mover 2021 microgrant”. It was the backing up and confidence placed in our expertise by WeRobotics and Skydio that made us committed to making this microgrant project a success. We would also like to express our sincere thanks to the District Administrative Office (Bhaktapur), Mr. Siddhant Neupane – IT Officer at Changunarayan Municipality, and the overall leadership at the Changunarayan Municipality Office for the support letters and recommendations to the authorities that helped us to secure the necessary permissions and coordinate with the local stakeholders to facilitate the entire project. Also, sincere thanks to Skydio Technical Team for the continuous technical support and guidance throughout the project.
Our sincere thanks to the Department of Archaeology (DoA) for believing in the purpose of the project and coordinating with us on and off the field to ensure the project outcomes were obtained in time. We are highly grateful that the DoA has a strong belief that such projects could add a lot of value to the current reconstruction efforts of cultural heritage sites of Nepal and is willing to consider future partnerships in making such projects a regular thing.
Sincere thanks to the local communities, Temple Preservation Committee, and APF Security Officials we worked with during the 3D capture for cooperating with us during the entire course of this project and bearing with the inconveniences. Last but certainly not least, sincere thanks to NAXA Pvt. Ltd. for the technical support and resources during the processing stage to prepare the final 3D model.
Thanks to the cooperation of the overall consortium, community participation, and the municipality’s strong leadership, the project proved to be a success: The Government of Nepal is now interested in replicating this project in different parts of Nepal.