SfM digital surface model and orthomosaic representing Head of the Meadow Beach, Truro, MA on March 20, 2024

DSM was created in Agisoft Metashape v. 2.1.0 using the following general steps (see Over and others, 2021):
1. Metashape project was created with imagery (located in larger work citation 2024-011-FA_HOM_f1.zip). Photos were aligned at a low accuracy and then GCPs were automatically detected in the point cloud. Nine GCPs (2024-011-FA_HOM_GCPs.csv) were located.
2. GCP horizontal and vertical accuracy was set to 0.01/0.02 m. The photos were re-aligned with high accuracy (the pixels are not subsampled for increased processing speed) using a keypoint limit of 40,000 and unlimited tie points.
3. Metashape software refined and optimized, using least squares, the camera positions, GCPs, and lens model using gradual selection and optimization parameters of: Reprojection uncertainty = 20, Projection accuracy = 5, and Reprojection error = 0.3 to minimize the distance between the measured points and the software created points (see Over and others, (2021) for a detailed discussion on these parameters).
4. A dense point cloud was generated using high-quality (images are not subsampled) and a low frequency filtering algorithm. The dense point cloud was then edited by hand to remove erroneous points before generating a DSM with interpolation disabled.
5. The DSM was then exported (2024-011-FA_HOM_DSM_UTM19N_NAVD88_10cm) from the software at a resolution of 10 cm in NAD83(2011)/UTM Zone 19N and NAVD88 (m)
6. A second DSM with interpolation enabled was created and from that surface an orthomosaic using the RGB averaged method was created. The orthomosiac was then exported ((2024-011-FA_HOM_RGBavg_UTM19N_10cm) from the software at a resolution of 10 cm in NAD83(2011)/UTM Zone 19N.