Structure from motion GCPs, digital surface model, and orthomosaic representing Marconi Beach, Wellfleet, MA on March 22, 2024

The ground control points were processed with the following steps:
1. Ten AeroPoint 2s were deployed evenly spaced across the survey area. AeroPoint 2s were left on for ~3 hours to collect GNSS data.
2. Once connected to Wifi, the AeroPoint 2 data were uploaded and run through a post-processing kinematic algorithm of the CORS network to get a global accuracy. The data were exported with xyz variances in the horizontal datum NAD83(2011) to produce latitude, longitude, and ellipsoid heights, and then UTM19N and NAVD88 using Geoid 18 was used to produce orthometric heights. These are exported to a CSV file and named 2024-016-FA_Marconi_GCPs.csv.

DSM and orthomosaic was created in Agisoft Metashape Pro v. 2.1.0 using the following general steps (see Over and others, 2021 for details):
1. Metashape project was created with imagery (located in larger work citation 2024-016-FA_Marconi_imagery.zip). Photos were aligned at a low accuracy and then GCPs were automatically detected in the point cloud. The ten GCPs were located and location information added using the CSV file from the previous step.
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 (2024-016-FA_Marconi_DSM_UTM19N_NAVD88_5cm.tif).
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_5cm.tif).
7. Products were Adobe deflate compressed and cloud optimized using gdal_translate with the following command: for %i in (.\*.tif) do gdal_translate %i .\%~ni_cog.tif -of COG -stats -co BLOCKSIZE=256 -co COMPRESS=DEFLATE -co PREDICTOR=YES -co NUM_THREADS=ALL_CPUS -co BIGTIFF=YES (v. 3.1.4 accessed October 20, 2020 https://gdal.org/), where i is the name of each GeoTIFF.