Beach Profile Data Collected from Isla Verde, Puerto Rico (March 23, 2023)

PLANNING Transects were created using the MathWorks® MATLAB R2024a computing environment. Cross-shore transects were planned perpendicular to the beach by utilizing a measured 2018 lidar shoreline (Doran and others, 2017) to find a shoreline angle. This resulted in 48 cross-shore transects (lines 17 to 64) spaced approximately 10 meters (m) apart and spanning approximately 470 m in the alongshore direction. Five alongshore transects (lines 1 to 5), spanning the length of the study area, were cast approximately 10 m apart in the cross-shore, spanning from the dune toe to the shoreline. Transect line planning was done in a similar way to Brown and others (2018).

ACQUISITION Transect lines were surveyed, on foot, by a person equipped with a GNSS receiver and a GNSS antenna affixed to a SECO© surveying backpack, which was connected to a Windows laptop PC running HYPACK 2022 survey acquisition software. Post-processed kinematic GNSS data were recorded at 5 hertz (Hz) with an Ashtech™ ProFlex™ 500/800 GNSS receiver and an Ashtech™ GNSS geodetic survey antenna for the cross-shore transects and a Spectra Precision SP90 GNSS receiver and antenna for the alongshore transects. The time associated with the beginning and end of surveying each transect line was recorded on the laptop in HYPACK® by the surveyor. These data acquisition steps are similar to those reported by Brown and others (2018). For this survey, 48 cross-shore transects (lines 17 to 64) and 5 alongshore transects (lines 1 to 6; except for line 5) were collected.

GNSS POST-PROCESSING Raw GNSS post-processed kinematic data recorded on the surveying receiver was post-processed using GNSS post-processing software GrafNav (Waypoint Product Group) version 9.0. The GNSS data recorded by the surveying receiver were processed in NAD 83 geographic coordinates to concurrent static GNSS data recorded by a local base station of known position (NAD 83). The base station used was a Trimble® Alloy GNSS receiver and Trimble® TRM115000.00 GNSS geodetic survey antenna at a station within the National Oceanic and Atmospheric Administration's Continuously Operating Reference Stations (CORS) Network at San Juan, Puerto Rico, with site ID N240 (https://geodesy.noaa.gov/CORS/ncn_station_pages/index.html?stationID=N240). The final, differentially-corrected, precise GNSS positions were exported from GrafNav in American Standard Code for Information Interchange (ASCII) text format, with projected horizontal coordinates in NAD 83, UTM Zone 20N, and vertical coordinates in PRVD02, GEOID18. These post-processing steps are similar to those reported in Brown and others (2018).

DATA PROCESSING Beach profile horizontal position and elevation data for each individual transect were extracted from the post-processed GNSS data based on the surveying times recorded with HYPACK® using the MathWorks® MATLAB R2024a computing environment. The elevation data were adjusted by subtracting the elevation of the GNSS antenna above the ground when attached to the surveying backpack during the survey. The antenna height corresponding to lines 1, 2, 4 and 6 is 1.77m and the antenna height corresponding to lines 3 and 17-64 is 1.315m. The data were smoothed in the cross-shore direction to reduce the noisiness of the data, similar to the smoothing method done by Stockdon and others (2009). The noisiness is due to the high temporal sampling frequency and the walking motion of the human surveyor. The choice of a moving 1-m wide Hanning filter (Blackman and Tukey, 1959) was sufficient to reduce noise along the profile while preserving the elevation of the profile. The data were quality-controlled in MATLAB to remove invalid data points by eliminating points with poor GNSS data quality, visually inspecting plots of horizontal positions and discarding points not on the cross-shore beach profile lines (e.g., points just prior to and just after a transect), and visually inspecting plots of elevation and discarding points with erroneous GNSS data (e.g., spikes in the GNSS data). The final beach profile data were written to individual text files (.xyz) in tabular format, with columns representing: 1) Easting (NAD83, UTM Zone 20N), 2) Northing (NAD83, UTM Zone 20N), and 3) Orthometric Elevation (PRVD02, GEOID18).