Tandoc Drone Photo 6

In July 2022, the team arrived in Tamban port with Father Eric, the Bicol Archaeological Project’s (BAP) primary community contact and a representative of the Catholic Church, and Earl Hernandez, a Bikolano and fellow BAP researcher. We did a survey of the town and took GPS points for a large concrete slab that was a component of the old rail platform and for a concrete foundation of a crane that was used to load and unload logs. Both structures were nestled between and beneath people’s homes and businesses. From an interview with Annie Cabral, captain of the barangay—head of the smallest political unit in the Philippines—we learned about the status of land reclamation in Tamban and subsequent erosion on the opposite bank, as well as the ongoing challenges facing development efforts in the barangay: expanding settlement, erosion, and flooding. We also learned that the rail line used to run along the river and bring in lumber from Lagonoy. Tebbe’s (1967) account corroborates the existence of a port at this location, near the first Cadwallader-Gibson logging camp, Camp Isarog, so named for its views of Mount Isarog. We conducted one drone flight over Tamban. The lidar data were not as clean as we would have liked due to the high humidity and visible water vapor in the air, but this scan still produced a detailed elevation model.

It is important to rely on local people’s definition of flooding, because the risk associated with seasonally rising waters can be subjective. Cabral indicated the elevation below which flood waters put homes and businesses at risk. The extent of flood risk became clearer when we combined this community-sourced flood elevation with the elevation model derived from the lidar scan. Using aerial photos and the orthomosaic of the town in ArcGIS, we calculated the total area of the town that included modern buildings and then the percentage of that area lying below the elevation at risk of flooding. We found that the flood plain extends to endanger 28.5% of the occupied area of Tamban.

Two days after our arrival in Tamban, Hernandez, Father Eric, and Meyer-Lorey visited Tandoc. We met up with local Catholic priest Father Serafin Amaro and conducted a ground survey, taking 32 GPS points of concrete and iron structures that belonged to Jacob Chetvernia’s Woodworks plywood operation. We circled the two artificial freshwater lakes built by the plywood company and examined the pier, which once was a wooden rail platform and is now a concrete promontory.

This project used remote-sensing techniques (satellite imaging, historical aerial photography, drone lidar, and drone photography); ethnography (interviews, place-name analysis, and community input); ground survey; mapping; and historical research. Yet, “low-impact” and “nondestructive” methods do not necessarily mean “nondisruptive” methods; even low-impact methods involve some level of communication with stakeholders. Being part of an archaeological project with significant existing community partnerships helped a great deal in creating positive attitudes toward drone flights and the deliverables they produced. 

Remote sensing was our method of choice not only because it is low impact but also because it is practical: an inexpensive drone equipped with a camera or a lidar sensor can gather data for use in monitoring forests, tracking human ecological impacts, gauging land use, and finding archaeological sites (Anderson et al. 2019).

Our archaeological applications of remote sensing were informed by Chase and colleagues’ (2011) use of lidar for studying land modification; Acabado and coworkers’ (2019) use of photogrammetry for 3D mapping to display the extent of modern rice terraces in Ifugao, Hammer and Ur’s (2019) use of archival aerial photos for landscape archaeology, and Larrain and colleagues’ (2021) approach using local high school students to aid researchers in mapping Inka architecture. With collaboration from Partido State University and local community members, we used a combination of these approaches to facilitate data collection.

The Zenmuse L1 lidar sensor mounted to a Matrice 300 RTK drone with an Emlid Reach RS+ RTK base station enabled high-resolution aerial photography of the long-term effects of deforestation, with photogrammetry and lidar data targeted at 3D mapping of specific points of interest: defunct rail lines, lumber-processing factories, and workers’ settlements. Lidar data were processed through DJI Terra, LiDAR360, and ArcGIS Pro. Photogrammetry was processed using Agisoft Metashape. At Tamban we flew a combined lidar and photogrammetry mission at 200 m. Rain caused minor interference with the lidar data. At Tandoc we flew two lidar missions to map the barangay (ward or district) and detect industrial remains through tree cover. We then flew one photogrammetry mission to generate an orthomosaic of the nearby barangay Homestead and generated two orthomosaics from RGB data collected during lidar flights over Tandoc. We determined that, given the scale of the route, satellite imaging and interviews would be more efficient for investigation of the road and the settlements along it.

We conducted several drone flights over Tandoc and the nearby settlement of Homestead. We took aerial photos of Homestead and Tandoc and did two lidar scans of Tandoc, one to cover the whole settlement and one low, slow flight targeted on the center of the industrial remains. These photos show the extent of the artificial freshwater lakes, factory structures, and current buildings through tree cover. The effects of deforestation and cash cropping are visible as well: after clear-cutting, rapid erosion from rains leaves thin clayey soil that can no longer support larger trees like hardwoods. There are now stretches of reddish soil, low grasses, or palm  lantations established to produce profitable crops—bananas, coconuts, copra, palm oil, and abaca fiber—from depleted soil.