Orthomosaic representing Head of the Meadow Beach, Truro from images collected during field activity 2021-014-FA on February 4, 2021

The orthomosaic was created in Agisoft Metashape v. 1.7.2 using the following general steps (see Over and others, 2021 for a more detailed methodology explanation): 1. The project was created and imagery (located in larger work citation 2021014FA_Truro_f1.zip) and positions (located in larger work citation 2021014FA_Truro_f1_photolocations.csv) were imported using the NAD83(2011) datum. 2. Accuracies for the ground control points (GCPs) were set 0.05 m and accuracies for the camera positions were set to 1 m. The photos were aligned with high accuracy (the pixels are not subsampled for increased processing speed) using a keypoint limit of 50,000 and unlimited tie points. 3. Ten GCPs (2021014FA_Truro_nav_AeroPoints.csv located in the larger work citation) were added to the project in NAD83(2011) and manually placed on the images as markers. 4. The alignment process matches pixels between images to create point clouds and puts the imagery into a relative spatial context using the photo positions and GCPs. Then, Metashape software refined and optimized, using least squares, the camera positions and lens model using gradual selection and optimization parameters of: Ru = 15, Pa = 5, and Re = 0.5 to minimize the reprojection error or the distance between the measured points and the software created points. 5. A dense point cloud was generated using the high quality setting (images were not subsampled) and a low frequency filtering algorithm. The total camera position error was 5 m (XYZ: 2.16, 4.25, 0.99) and the total GCP error was 0.019 m (XYZ: 0.010, 0.010, 0.012). The dense point cloud was then edited to remove noise by filtering by point confidence before generating an interpolated digital elevation model (the software calls all models elevation models, but technically it is a surface model because it includes vegetation/canopy returns, a terrain model would be only bare earth returns). 6. The digital surface model was used to build an orthomosaic, which was then exported from the software at a resolution of 10 cm and in NAD83(2011)/UTM Zone 19N (ESPG:6348) and GEOID 18B NAVD88 in meters.

Update the publication date to 'go live' date. Modified browse graphic name to be the URL to the browse graphic. This work done on 20220307. Added PID to metadata (20220411). Any edits to the metadata also include an update to the metadata date.