by India Mackinson, Intern, UNC Institute for the Environment, Outer Banks Field Site
With each passing day, new technologies revolutionize yet another field or industry, and the Pappy’s Lane shipwreck project is no exception. While the research team did great work on mapping the wreck through snorkeling and meticulous recording, they got some help from another valuable team member–a drone. Flown by UNC CSI’s director of education and outreach, John McCord, the drone captures high-quality images and video of the wreck that a person on the ground could never get. The images the drone captures goes into three important aspects of the project: outreach, mapping, and 3D modeling.
The drone aerial photographs and videos help the public interact with the project in a way that wouldn’t be possible without it. From the shore, the Pappy’s Lane shipwreck is barely visible with only the stern and sets of flags at either end marking its place rising above the waterline. Even up close, it’s hard to get a good sense of what the wreck used to be before degrading to the brittle, oyster-encrusted skeleton it is today. The drone photographs and footage connect the dots between the wreck resting in the Pamlico Sound and the World War II gunboat that patrolled the Pacific, showing the outline of the wreck that more clearly matches that of a vessel.
While the research team spent weeks thoroughly measuring and recording the wreck to create a complete map of the site, some discrepancies in details are destined to arise during the transfer from the field to the lab, which is where the drone can help. It produces high-quality snapshots that make perfect reference material to answer any arising questions in mapping. The team can consult the images to resolve any conflicting information rather than making the trip to the site in Rodanthe. The up-to-date aerial images also supplied information on the cover and depth of sediment, oysters, and submerged aquatic vegetation on the wreck, which assisted in planning and permitting the project.
The drone’s most innovative application in the project is 3D modeling through photogrammetry. Photogrammetry uses photographs to make a point cloud in virtual space based on the camera’s calibration and pose, which software then connects to form a geometrical mesh. From there, textures are created on the surface of the model using color information from the original photographs, giving you an accurate, detailed model of an object or area.
The drone makes gathering the images for the 3D model straightforward, getting data in its 15 to 25-minute flight that would take weeks otherwise. Programming the flight path beforehand also automates the process and ensures that every point required for the model is captured. For the model of the Pappy’s Lane shipwreck, 400 photos were taken and 164 were used to create it.
While using the drone to create a 3D model is relatively efficient and easy to do, there are limitations that will keep this method from permanently replacing researchers in the field. In general, areas that are dark, shiny, or thin have trouble translating from photographs to a 3D model, requiring extra photographs of that area to correct it. For this project, the weather is also an obstacle. Still wind and flat water create the best results. The Pappy’s Lane shipwreck also lies mostly underwater with low visibility. UNC CSI researchers are experimenting with polarizing lenses on the drone to get greater water penetration and to potentially see more of the site. The polarizing lens can only be fixed to the drone camera at a certain angle, therefore limiting the angle of clear photographs the drone can take.
The research team hopes to make a model that better represents the Pappy’s Lane wreck in the future for both outreach and research purposes. Applications for the 3D model in the field and in this project are only just beginning to be explored, including possibilities in virtual reality immersion. With the 3D model, not only can aspects of the wreck be preserved forever, but more people can see and interact with it than ever before.