Topographic data, aerial imagery, and GPS data collected during uncrewed aircraft system (UAS) operations at Sesuit Marsh, Dennis, Massachusetts, August 12, 2024

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Frequently anticipated questions:

What does this data set describe?

Title:
Topographic data, aerial imagery, and GPS data collected during uncrewed aircraft system (UAS) operations at Sesuit Marsh, Dennis, Massachusetts, August 12, 2024
Abstract:
Small Uncrewed Aircraft Systems (sUAS) were used to collect aerial remote sensing data over Sesuit Marsh in Dennis, MA. Raw data from aerial surveys include aerial images from natural color (RGB) and multispectral cameras and raw lidar data. These datasets were processed to produce high resolution digital elevation models (DEM), image mosaics, and lidar point clouds (LPC) to provide local partners with high resolution imagery and elevation data to monitor and identify vegetation cover of a salt marsh on Cape Cod during peak growing season. A YellowScan Mapper Plus lidar system with integrated RGB camera module were mounted to a DJI Matrice 600 to collect the raw lidar data and true-color imagery. A MicaSense Altum-PT was then mounted to the DJI Matrice 600 to collect the multispectral reflectance imagery. Black and white cross-coded ground control points (GCPs) were surveyed using RTK-GPS and RTK-enabled AeroPoints to georeference the model and orthomosaics during post-processing. This project was supported by grant funding from the Commonwealth of Massachusetts' Executive Office of Energy and Environmental Affairs, Division of Conservation, awarded to Rick Rheinhardt in collaboration with the Cape Cod Conservation District.
Supplemental_Information:
These data were collected by the USGS Coastal and Marine Hazards and Resources Program under USGS field activity number 2024-021-FA. The field activity webpage (https://cmgds.marine.usgs.gov/services/activity.php?fan=2024-021-FA) contains additional information regarding the field activity.
  1. How might this data set be cited?
    Cramer, Jennifer M., Brosnahan, Sandra M., Ackerman, Seth D., Over, Jin-Si R., Millo, Amit, and Rheinhardt, Rick, 20250620, Topographic data, aerial imagery, and GPS data collected during uncrewed aircraft system (UAS) operations at Sesuit Marsh, Dennis, Massachusetts, August 12, 2024: data release DOI:10.5066/P1EPMT7Y, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    Other_Citation_Details:
    Cramer, J.M., Brosnahan, S.M., Ackerman, S.D., Over, J.R., Millo, A., and Rheinhardt, R., 2025, Topographic data, aerial imagery, and GPS data collected during uncrewed aircraft system (UAS) operations at Sesuit Marsh, Dennis, Massachusetts, August 12, 2024: U.S. Geological Survey data release, https://doi.org/10.5066/P1EPMT7Y.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.17597
    East_Bounding_Coordinate: -70.15988
    North_Bounding_Coordinate: 41.74948
    South_Bounding_Coordinate: 41.74145
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/67c9df85d34ed3737708ca1a?name=Landing_browse.jpg&allowOpen=true (JPEG)
    Browse image showing reflectance orthomosaic of Sesuit Marsh in Dennis, MA
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 12-Aug-2024
    Currentness_Reference:
    Ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: digital image, point cloud, raster, and tabular digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 19
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -69.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 0.001
      Ordinates (y-coordinates) are specified to the nearest 0.001
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum of 1983 (National Spatial Reference System 2011).
      The ellipsoid used is GRS_1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    2024021FA_Sesuit_Aug2024_AeroPoints.csv
    Ground control point positions, elevations, and attributes (Source: USGS)
    FAN
    USGS Field Activity Number (Source: USGS)
    ValueDefinition
    2024-021-FAYear, USGS ID, and Field Activity
    Date
    Calendar date of collection (Source: USGS)
    ValueDefinition
    20240812YYYYMMDD
    Point ID
    Unique point identification number. (Source: USGS)
    Range of values
    Minimum:1
    Maximum:6
    Attributes
    Unique identifier for individual AeroPoints. (Source: Processor Defined) Character string.
    Latitude NAD83[2011]
    Post-processed latitude of AeroPoint position (NAD83[2011]). (Source: Processor Defined)
    Range of values
    Minimum:41.74396111
    Maximum:41.74666363
    Units:decimal degrees
    Longitude NAD83[2011]
    Post-processed longitude of AeroPoint position (NAD83[2011]). (Source: Processor Defined)
    Range of values
    Minimum:-70.17038947
    Maximum:-70.16290589
    Units:decimal degrees
    Ellipsoid NAD83[2011]
    Post-processed height in meters of AeroPoint in relation to the NAD83(2011) reference ellipsoid. (Source: Processor Defined)
    Range of values
    Minimum:-27.104
    Maximum:-23.302
    Units:meters
    Northing 19N
    Post-processed interpolated Y-coordinate of AeroPoint in NAD83(2011)/UTM Zone 19N. (Source: Processor Defined)
    Range of values
    Minimum:4622007.393
    Maximum:4622310.671
    Units:meters
    Easting 19N
    Post-processed interpolated X-coordinate of AeroPoint in NAD83(2011)/UTM Zone 19N. (Source: Processor Defined)
    Range of values
    Minimum:402686.736
    Maximum:403307.021
    Units:meters
    Orthometric NAVD88
    Post-processed Z-coordinate of AeroPoint using NAVD88 with Geoid 18 applied. (Source: Processor Defined)
    Range of values
    Minimum:0.878
    Maximum:4.682
    Units:meters
    Xvar mm
    Internal variance in the X-coordinate from post-processing. No data value is NaN. (Source: Processor Defined)
    Range of values
    Minimum:4.0
    Maximum:7.9
    Units:millimeters
    Yvar mm
    Internal variance in the Y-coordinate from post-processing. No data value is NaN. (Source: Processor Defined)
    Range of values
    Minimum:4.2
    Maximum:7.6
    Units:millimeters
    Zvar mm
    Internal variance in the Z-coordinate from post-processing. No data value is NaN. (Source: Processor Defined)
    Range of values
    Minimum:6.8
    Maximum:13.6
    Units:millimeters
    Baseline distance km
    Distance to from the AeroPoint to the correcting base. (Source: Processor Defined)
    Range of values
    Minimum:0.05
    Maximum:17.36
    Units:kilometers
    2024021FA_Sesuit_Aug2024_aPT_ImageLocs.csv
    Comma Separated Value (CSV) file containing data. (Source: Producer Defined)
    SourceFile
    File names of individual images, see the Process Description for file naming convention. (Source: USGS) Character string.
    PreservedFileName
    File names copied from the SourceFile tag to preserve the original file name once image is uploaded to the Imagery Data System (IDS). (Source: USGS) Character string.
    GPSMapDatum
    The EPSG code for the coordinate system of the images. (Source: Processor Defined) Character string.
    GPSLatitude
    Latitude (x) in WGS84 of camera based on time of each image capture. Positive values represent north coordinates. (Source: Processor Defined)
    Range of values
    Minimum:41.7435861
    Maximum:41.7474445
    Units:decimal degrees
    GPSLongitude
    Longitude (y) in WGS84 of camera based on time of each image capture. Negative values represent west coordinates. (Source: Processor Defined)
    Range of values
    Minimum:-70.1731709
    Maximum:-70.1627096
    Units:decimal degrees
    Map Datum (UTM)
    The geographic coordinate system of the image locations transformed to NAD83(2011) UTM coordinates. (Source: Processor Defined) Character string.
    Northing
    Northing coordinate in NAD83(2011) / UTM zone 19N of the image in meters. (Source: Processor Defined)
    Range of values
    Minimum:4621966.924
    Maximum:4622395.190
    Units:meter
    Easting
    Easting coordinate in NAD83(2011) / UTM zone 19N of the image in meters. (Source: Processor Defined)
    Range of values
    Minimum:402453.206
    Maximum:403321.439
    Units:meter
    2024021FA_Sesuit_Aug2024_YSMP_ImageLocs.csv
    Comma Separated Value (CSV) file containing data. (Source: Producer Defined)
    SourceFile
    File names of individual images, see the Process Description for file naming convention. (Source: USGS) Character string.
    PreservedFileName
    File names copied from the SourceFile tag to preserve the original file name once image is uploaded to the Imagery Data System (IDS). (Source: USGS) Character string.
    GPSMapDatum
    The EPSG code for the coordinate system of the images. (Source: Processor Defined) Character string.
    GPSLatitude
    Latitude (x) in WGS84 of camera based on time of each image capture. Positive values represent north coordinates. (Source: Processor Defined)
    Range of values
    Minimum:41.7436
    Maximum:41.74746
    Units:decimal degrees
    GPSLongitude
    Longitude (y) in WGS84 of camera based on time of each image capture. Negative values represent west coordinates. (Source: Processor Defined)
    Range of values
    Minimum:-70.17314
    Maximum:-70.16284
    Units:decimal degrees
    Map Datum (UTM)
    The geographic coordinate system of the image locations transformed to NAD83(2011) UTM coordinates. (Source: Processor Defined) Character string.
    Northing
    Northing coordinate in NAD83(2011) / UTM zone 19N of the image in meters. (Source: Processor Defined)
    Range of values
    Minimum:4621968.431
    Maximum:4622396.813
    Units:meter
    Easting
    Easting coordinate in NAD83(2011) / UTM zone 19N of the image in meters. (Source: Processor Defined)
    Range of values
    Minimum:402455.781
    Maximum:403311.483
    Units:meter
    2024021FA_Sesuit_Aug2024_YSMP_LPC.laz
    YSMP lidar point cloud in .laz file format from flights over the Sesuit Marsh. This georeferenced point cloud was colorized using the natural color RGB orthomosaic and has classified ground points. Total point count is 103,735,392. The point density is 423.08 ppsqm, and point spacing is 0.047 m. (Source: producer defined)
    Elevation
    Surface elevation orthometric height NAVD88 (m) using Geoid 18 in NAD83(2011)/UTM Zone 19N. (Source: YellowScan CloudStation)
    Range of values
    Minimum:-1.243
    Maximum:34.714
    Units:meters
    Intensity
    Lidar intensity is recorded as the return strength of a laser beam during data collection. (Source: YellowScan CloudStation)
    Range of values
    Minimum:0
    Maximum:65,025
    2024021FA_Sesuit_Aug2024_YSMP_DSM_5cm_cog.tif
    A cloud-optimized digital surface model gridded from the "2024021FA_Sesuit_Aug2024_YSMP_LPC.laz" lidar point cloud ground classified points with encoded elevation values. Pixel resolution is 5 cm and elevation units are meters. No data value is -3.4028e+38. (Source: USGS)
    Value
    Surface elevation orthometric height NAVD88 (m) using Geoid 2018 in NAD83(2011) UTM Zone 19N. (Source: producer defined)
    Range of values
    Minimum:-1.227
    Maximum:34.714
    Units:meters
    2024021FA_Sesuit_Aug2024_YSMP_DTM_5cm_cog.tif
    A cloud-optimized digital terrain model gridded from the "2024021FA_Sesuit_Aug2024_YSMP_LPC.laz" lidar point cloud ground classified points with encoded elevation values. Pixel resolution is 5 cm and elevation units are meters. No data value is -3.4028e+38. (Source: USGS)
    Value
    Terrain elevation orthometric height NAVD88 (m) using Geoid 2018 in NAD83(2011) UTM Zone 19N. (Source: producer defined)
    Range of values
    Minimum:-1.227
    Maximum:14.540
    Units:meters
    2024021FA_Sesuit_Aug2024_YSMP_Ortho_5cm_cog.tif
    A cloud-optimized 3-band true-color orthomosaic. Pixel resolution is 5 cm. (Source: producer defined)
    Band_1
    Red wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:255
    Units:none
    Band_2
    Green wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:255
    Units:none
    Band_3
    Blue wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:255
    Units:none
    2024021FA_Sesuit_Aug2024_aPT_Ortho_5cm_cog.tif
    A cloud-optimized 5-band multispectral reflectance orthomosaic. Values can be greater than 1 due to oversaturation. Pixel resolution is 5 cm. No data value is -32,767.0. (Source: producer defined)
    Band_1
    Blue wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:1.332
    Units:none
    Band_2
    Green wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:1.942
    Units:none
    Band_3
    Red wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:1.519
    Units:none
    Band_4
    Rededge wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:3.731
    Units:none
    Band_5
    Near infra-red wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:6.144
    Units:none

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Jennifer M. Cramer
    • Sandra M. Brosnahan
    • Seth D. Ackerman
    • Jin-Si R. Over
    • Amit Millo
    • Rick Rheinhardt
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Jennifer M. Cramer
    U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
    Geographer
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 x2314 (voice)
    jcramer@usgs.gov

Why was the data set created?

Lidar data were collected due to the technology's ability to penetrate vegetation canopy and provide accurate digital terrain models (DTMs). Aerial imagery was collected with appropriate resolution and overlap to permit high-quality photogrammetry and generation of digital surface models (DSM) and orthoimagery. Multispectral imagery was collected to aid in vegetation classification workflows.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 12-Aug-2024 (process 1 of 8)
    RTK-GPS Base Station: A Spectra Precision model SP80 GNSS base station receiving real-time differential corrections from the satellites was set up to collect positions in RINEX format at 1 hz on a known point prior to and for the duration of lidar data surveys. The RTK receiver for base is linked via Bluetooth to a handheld data collector (Carlson CHC LT30 Handheld Terminal running Carlson SurvCE v. 4.06 software under Windows Mobile v. 6.1 Professional operating system). Rover antennas were mounted on 2 m survey rods with bubble levels and 5 cm (2 inch) sand feet. Conversions from satellite coordinates to NAD83(2011) UTM zone 19N (EPSG::6348) and NAVD88 (EPSG::5703) were made by Carlson SurvCE software in the data collector.
    Date: 12-Aug-2024 (process 2 of 8)
    Ground control: AeroPoint targets were emplaced on flat, stable surfaces, with clear view of the sky and left undisturbed, collecting data for at least 2 hours. Aeropoint data was uploaded via a WiFi connection to a user defined account on propelleraero.com. The raw data are processed by Propeller and exported to a CSV file in NAD83(2011) UTM zone 19N (EPSG::6348) for horizontal and NAVD88 (geoid 18) (EPSG::5703) for vertical.
    Date: 12-Aug-2024 (process 3 of 8)
    LiDAR System: A YellowScan Mapper Plus (YSMP) high-density LiDAR system containing a LiDAR sensor and natural color RGB camera module was mounted to a DJI Matrice 600 (M600) uncrewed aircraft system (UAS) to collect low-altitude aerial LiDAR point cloud (LPC) data and simultaneous overlapping true-color (RGB) images. A configuration text file (CONFIG.TXT) is pre-loaded onto the lidar USB thumb drive and was edited to control LiDAR and camera module settings, including the camera triggering height, the camera triggering interval, and the LiDAR scan pattern. For this field area over marsh and forested terrain the scan pattern was set to non-repetitive (spirograph). The flight plans for this project targeted a swath overlap of 50% with the following flight parameters: altitude of 61 m, flight line spacing at 45 m, a velocity of 10 m/s, and a 3-second camera triggering interval. At these parameters, a lidar point density of ~300 points per square meter (ppsqm) and a sidelap and forelap for natural color RGB camera module for colorization of the LPC in post-processing of 50% can be achieved. For every lidar UAS flight, the following steps were followed to properly operate the system and collect data: After powering on the UAS and LiDAR system, the GPS, scanner, and camera module all must initialize. After takeoff, an additional initialization pattern must be manually flown by the pilot to signal to the IMU to begin collecting LiDAR data. This pattern consists of a forward, back, and forward flight path ending with a hook-shaped coordinated turn on the last forward maneuver. It is best practice that this is flown below the camera triggering altitude. Once the maneuver is completed, the UAS is ascended to the camera triggering altitude where the RGB camera module sets the ISO (International Standard Organization), or the camera sensitivity to light,for the entire flight. It is recommended to make this altitude close to the flight plan altitude. The mission is uploaded to the UAS and it begins the automated flight plan. When the data collection is finished or batteries require swapping, the same initialization pattern flown at the beginning is flown again to de-initialize the scanner. The LiDAR data are saved to a 256 GB USB thumb drive in three different files: (1) the IMU+GPS data, decimated for quick post-processing, in binary *.ys format, (2) the scanner data in *.lvx format (~600 MB per minute of data collection), (3) and the complete IMU+GPS data in Applanix (Trimble) binary *.t04 format. The RGB images are saved to a 64 GB microSD card as *.jpeg files. The camera triggering time-interval was determined and set based on the focal length and ground sampling distance (GSD) of the camera as well as the altitude and speed of the UAS in order to achieve ~50% forelap between adjacent photos for colorizing the LiDAR point cloud. The camera triggering interval as determined for the flight plans as well as the altitude at which the camera automatically sets the ISO (usually set at 5 - 10 meters lower than the flight plan altitude) for the scene is written into a configuration file located on a USB stick that is plugged into the YellowScan Mapper Plus system.
    Date: 12-Aug-2024 (process 4 of 8)
    Altum-PT: A Micasense Altum-PT 7-band camera was mounted to the underside of a DJI Matrice 600 UAS using a 4-pin cable and pointed nadir. The camera receives power from the UAS batteries when the UAS is powered on. The camera is operated from the Micasense Web Configuration Page, a webpage accessed through a Wi-Fi signal originating from the camera. The camera is set to record images at a 2-second interval. The SD card is inserted into the camera and reformatted using the Micasense Web Configuration Page before every flight. Just prior to takeoff, a Micasense calibration panel was placed under the camera for several seconds to capture calibration images. Immediately following landing, the Micasense calibration panel was placed under the camera for several seconds to capture more calibration images. After each flight, the UAS is powered off, the SD card is removed, and all images and files relating to the survey are downloaded to a field computer.
    Date: 12-Aug-2024 (process 5 of 8)
    Lidar data processing: After each data collection, lidar files are stored on the USB thumb drive in a folder following a naming scheme of "YS-YYYYMMDD-HHMMSS" where YS is the acronym for YellowScan, YYYYMMDD is the date stamp, and HHMMSS is the time stamp in UTC time (e.g. YS-20230830-171402). Within this folder are the three files containing the IMU+GPS data in .ys and .t04 format and the scanner data in *.lvx format, which follow the same naming scheme as the parent folder. The RGB images are stored on the SD card following a naming scheme of DSC#####.JPG (e.g. DSC00001.JPG). Upon import of the raw scanner data (.ys file) for each flight to YellowScan CloudStation v. 2210.0.0, the sensor's Lidar (.profile) and Camera (.camera) profiles, provided by the vendor, are selected for the project and the project coordinate reference system is defined. CloudStation auto-identifies sensor position trajectories that are to be included in the model based on their length and linearity, but adjustments are usually required as the software will sometimes misidentify trajectories that should not be included, such as the path the UAS took to reach the first waypoint of the mission, or leave out paths that are considered too short. If there is a slight waver in a flight path, the software will sometimes cut off the ends of the flight paths. The .T04 file and base station GNSS RINEX file were used to correct and optimize the sensor position trajectories using the GNSS Inertial Processor and produce a Smoothed Best Estimate of Trajectory (SBET) file in .txt ASCII format, which represents the Post Processing Kinematic (PPK) Solution. The lever arm offsets and boresight angle corrections were applied to the LPC, along with a strip adjustment between transect swaths using CloudStation's "robust" setting. The LPC was then colorized using the images. The Cut Overlap function was applied to remove redundant points based on the closest parallel flight trajectory. The unclassified LPC model was then exported from CloudStation as a version 1.4 LAZ file. The LPCs were brought into Global Mapper (v. 26.0) and manually cleaned by reclassifying or removing points interpreted to be noise, points that were either not classified or incorrectly classified as ground, or were above a reasonable elevation threshold based on the surrounding features. The LPCs were exported as a 1.4 LAZ files. To produce the DSMs, the LPCs are gridded in Global Mapper using maximum values and exported to geotiff format. To produce DTMs, only the ground points are gridded using maximum values and exported to geotiff format. All files were exported in EPSG:6348 NAD83(2011)/UTM zone 19N and the vertical datum in EPSG:5703 NAVD88 height in meters using Geoid 18.
    Date: 12-Aug-2024 (process 6 of 8)
    Imagery processing: Telemetry navigation logs for each flight are exported from the Ignis app in GPX format. These telemetry logs are used to manually geotag the imagery from the YellowScan Mapper Plus camera modules in preparation for photogrammetric processing. Image timestamps must be adjusted to UTC time depending on timezone and daylight savings. These corrections were done using the program ExifTool. ExifTool uses linear interpolation to determine the position of the device at the time recorded in the image. This creates values for tags GPSLatitude, GPS LatitudeRef, GPSLongitude, GPSLongitudeRef, GPSAltitude, GPSTimeStamp, GPSDateStamp. A sample of code used to geotag images: exiftool -v2 -geotag ../../telemetry/Nav_FlightLogs/Flight\ Logs\ GPX/flight_log_2022_10_10_14_02_42_AGL.gpx -geosync=+16 '-geotime<${DateTimeOriginal}-04:00' -P f05XT2c/*.JPG. All images were renamed to ensure unique filenames following the USGS Coastal and Marine Hazards and Resources Program's best practices for image naming convention: "FieldActivityNumber_f##sensorID_YYYYMMDDTHHMMSS_OriginalFilename.tif" (e.g. "2024021FA_f01YSMP_20240812T153124Z_DSC01411.JPG") Field activity number is a unique identifier assigned to the field effort under which the data was collected (e.g. 2024021FA), f## denotes the flight in which the photos were taken (e.g. f07), sensor ID is the sensor or camera used to collect the imagery (e.g. YSMP = YellowScan Mapper Plus, aPT = Altum-PT), 'YYYYMMDD' is the UTC date, 'HHMMSS' is UTC time and the 'T' is used to separate the UTC date from UTC time, and the original filename is appended to the end. To ensure compliance with USGS Coastal and Marine Hazards and Resources Program's best practices for image exif, exif tags were added using a CSV containing header information for each photo. A sample of the code used to edit the image tags using ExifTool version 12.52:
    'exiftool -csv="C:\directory\name\EXIF.csv" C:\directory\name\of\photos *.[ext]
    The following tags were added to the image exif: -IPTC:Credit="U.S. Geological Survey" -IPTC:Contact="WHSC_data_contact@usgs.gov" -EXIF:Copyright="Public Domain" -XMP:UsageTerms="Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty." -EXIF:ImageDescription="https://cmgds.marine.usgs.gov/fan_info.php?fan=2024-021-FA; Low-altitude aerial photograph of Sesuit Marsh, Dennis, Massachusetts, taken with a YellowScan Mapper Plus RGB camera module during USGS field activity 2024-021-FA" -XMP:AttributionURL="https://doi.org/10.5066/P1EPMT7Y" -EXIF:GPSAreaInformation="camera-integrated GPS" -EXIF:GPSMapDatum="EPSG:4326 (WGS 84)" -IPTC:keywords="UAS Aerial Imagery; Sesuit; Dennis; Massachusetts; 2024-021-FA; USGS; YellowScan Mapper Plus" -EXIF:Artist="WHCMSC AIM Group" -XMP:PreservedFilename>Filename.
    The images for this data release have been uploaded to the Imagery Data System (IDS), which renames the images to safeguard from accidental overwriting. A user can restore the preserved filename with ExifTool. It is recommended to test on a single image before running on all images. To test on a single image:
    exiftool "-XMP:PreservedFilename<Filename" filename.tif.
    Once desired output is confirmed, use this code to rename all images in the folder: exiftool "-Filename<XMP:PreservedFilename" -overwrite_original -P *.tif *note that the case of the image extension may matter (e.g. TIF vs tif).
    CSV files corresponding to each sensor set of photos containing image location information was generated using ExifTool version 12.52. A sample of this code and the included tags:exiftool -n -csv -XMP:PreservedFilename -EXIF:GPSMapDatum -EXIF:GPSLatitude -EXIF:GPSLatitudeRef -EXIF:GPSLongitude -EXIF:GPSLongitudeRef *.JPG > 2024021FA_Clearview_Aug2024_YSMP_ImageLocs.csv
    Products generated from the images are standardly exported in NAD83(2011) / UTM coordinates so the original geotagged image coordinates were transformed and then appended to the image locations files to maintain consistent metadata information. ArcGIS Pro v. 3.3.0 was used to transform WGS84 coordinates to NAD83(2011)/UTM zone 19N using the project tool under the Data Management toolbox. In Excel v. 2408 (Build 17928.20512), The UTM Datum, Northing, and Easting Coordinates were appended as 3 additional columns to the image locations files for the Altum and YSMP files.
    Date: 12-Aug-2024 (process 7 of 8)
    Structure-from-motion processing: The SfM products were created in Agisoft Metashape v. 2.0.1 using the following general steps (see Over and others, 2021 for a more detailed methodology explanation): 1. A project was created in Metashape and imagery specific to each sensor and flight area were imported. 2. Photos were aligned at a low accuracy and then GCPs were automatically detected in the point cloud. GCP positions (2024021FA_Sesuit_Aug2024_AeroPoints.csv) were added to the project in the reference systems NAD83(2011)/UTM Zone 19N and NAVD88 (geoid 18). The horizontal and vertical accuracies for the GCPs were set to 0.045/0.055 m, respectively, and the camera positions for the images were turned off. The photos were then re-aligned with high accuracy (the pixels were not subsampled) using a keypoint limit of 60,000 and unlimited tie points. 3. The alignment process matched pixels between images to create point clouds and put the imagery into a relative spatial context using the GCPs. The resultant point clouds were filtered using one iteration of the 'Reconstruction uncertainty' filter at a level of 10, one iteration of the 'Projection accuracy' filter at a level of 3, and eight iterations of the 'Reprojection accuracy' filter to get to a level of 0.3. With each filter, iteration points are selected, deleted, and then the camera model was optimized to refine the focal length, cx, cy, k1, k2, k3, p1, and p2 camera model coefficients. 4. At this point, multiple ‘chunks’ were created so that a high-quality dense cloud with a low-frequency filtering algorithm could be made from the images. The dense point cloud was then edited by visual inspection and Metashape’s confidence filter to remove points with a low confidence near the edges and near water bodies. 5. A DSM is built from the dense point cloud and then an orthomosaic is built from the DSM with refined seamlines. The DSM and orthomosaic are exported in EPSG:6348 NAD83(2011)/UTM19N, the DSM has a vertical reference system in EPSG:5703 NAVD88 (Geoid 18).
    Date: 06-Dec-2024 (process 8 of 8)
    CLOUD OPTIMIZATION: All geoTIFF products were DEFLATE compressed and turned into a cloud-optimized GeoTIFFs (COG) using either the export tool in Global Mapper or gdal_translate with the following command: for %i in (.\*.tif) do gdal_translate %i .\cog\%~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 section. Person who carried out this activity:
    Jennifer M. Cramer
    U.S. Geological Survey, Woods Hole Coastal and Marine Science Center
    Geographer
    U.S. Geological Survey
    Woods Hole, MA

    508-548-8700 x2314 (voice)
    jcramer@usgs.gov
  3. What similar or related data should the user be aware of?
    Over, Jin-Si R., Ritchie, Andrew C., Kranenburg, Christine J., Brown, Jenna A., Buscombe, Daniel D., Noble, Tom, Sherwood, Christopher R., Warrick, Jonathan A., and Wernette, Phillipe A., 2021, Processing coastal imagery with Agisoft Metashape Professional Edition, version 1.6-Structure from motion workflow documentation: Open-File Report 2021-1039, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    This publication includes the general methodology for processing imagery in Metashape to produce digital surface models and ortho products.

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    Lidar point clouds: A YellowScan Mapper Plus high-density LiDAR system, containing a LiDAR sensor, inertial measurement unit (IMU), a GPS/GNSS antenna, and natural color RGB camera module, was mounted to a DJI Matrice 600 uncrewed aircraft system (UAS) to collect low-altitude aerial LiDAR point cloud (LPC) data and simultaneous overlapping true-color color images. GPS/GNSS data from real-time kinematic (RTK) base station collecting positions on a known point at 1-hz for the duration of the lidar surveys is used for post-processing kinematic (PPK) corrections of the lidar system trajectory positions. Accuracy of the point clouds can be influenced by the flight altitude, velocity, positions of satellites, terrain, overlap, and atmospheric conditions. Positional accuracy of the processed point cloud can be assessed using RTK-surveyed ground control points and checkpoints (see ground control and checkpoints section below). Horizontal accuracy can be difficult to assess due to difficulty visualizing the cross-checkered pattern of the ground control targets in the point cloud.
    Ground control and checkpoints: Ground control are highly visible, typically square, cross-checkered black and white (or light gray) targets that can be visible in aerial remote sensing data. RTK-GPS embedded, Wi-Fi enabled grey and black foam Propeller AeroPoints were used to collect continuous location and elevation data as ground control points. To improve visibility in the lidar point cloud, 2x2 meter square vinyl targets, with the same cross-checkered pattern as the AeroPoints were placed underneath the AeroPoints, with grey and black areas aligning.
    Elevation products: The positional accuracy of elevation and image mosaic rasters are typically determined from RTK-surveyed ground control points and check points. Ground control points are surveyed targets visible in aerial imagery that are used to georeference the model, while check points are independent of the model and can be used for post-validation. Ground control and checkpoints were collected at the Clearview Landfill survey location. Accuracy degrades toward the edges of the raster products due to the absence of ground control as well as the lack of overlap along the perimeter of the flight plan and angle of the images where the UAS is making a turn.
  2. How accurate are the geographic locations?
    Lidar data: Determining horizontal positional accuracy using ground control is difficult due to poor visualization of the center location of ground control targets in the LPC. Considering the GNSS reference accuracy of ~5 cm, a conservative horizontal positional error estimate could be considered up to 10 cm.
    Aerial Imagery: YellowScan Mapper Plus camera module images were manually geotagged using the drone telemetry logs (tlogs). The DJI M600 is equipped with a DJI A3 GPS, which receives signals from GPS and GLONASS satellites in WGS84 (EPSG::4326), but is otherwise uncorrected. The Altum-PT contains a u-blox NEO-M8 GNSS module within the DLS sensor, which receives signals from GPS and GLONASS in WGS84/EGM96. Horizontal locations are considered accurate to approximately 0.5 meters, but may be greater than 10 meters due to UAS flight path uncertainty. It is recommended to use the ground control points in the CSV files "2024021FA_Sesuit_Aug2024_AeroPoints.csv" for georeferencing.
    Structure-from-motion (SfM) processing: The RGB orthomosaic and multispectral reflectance orthomosaic have no elevation data associated with them. The horizontal X/Y RMSE of the orthomosaic from the Altum-PT multispectral imagery is 1.35 cm. The horizontal X/Y RMSE of the orthomosaic from the YellowScan Mapper Plus RGB imagery is 10.75 cm. The high error of the YSMP orthomosaic is likely due to poor overlap of images. Due to the flight line spacing being optimized for lidar collection, the images were only able to achieve ~50%.
    GPS Data: Horizontal positions for the AeroPoint targets are determined from the embedded RTK-GPS. The internal theoretical horizontal accuracy is 10 mm. The global horizontal accuracy is calculated using the following equation: global horizontal accuracy (mm) = internal horizontal accuracy (mm) + longest baseline distance (km) * 2. The resultant global horizontal accuracy of Aeropoint positions is 0.045 m.
  3. How accurate are the heights or depths?
    Lidar data: Using the AeroPoint targets as checkpoints, the LiDAR QC tool in Global Mapper v. 26.0 was used to determine the root mean square error (RMSE) of point cloud compared to the checkpoints. The point spacing was set to 3 (~12 cm), which averages the elevation value of points falling within a 3 point buffer from the checkpoint position. The vertical RMSE of the LPC determined from the checkpoint positions was 0.020 cm.
    Aerial Imagery: YellowScan Mapper Plus camera module images were manually geotagged using the drone telemetry logs (tlogs). The DJI M600 is equipped with a DJI A3 GPS, which receives signals from GPS and GLONASS satellites in WGS84 (EPSG::4326), but is otherwise uncorrected. The Altum-PT contains a u-blox NEO-M8 GNSS module within the DLS sensor, which receives signals from GPS and GLONASS in WGS84/EGM96. Vertical locations are considered accurate to approximately 0.5 meters, but may be greater than 10 meters due to UAS flight path uncertainty. It is recommended to use the ground control points in the CSV files "2024021FA_Sesuit_Aug2024_AeroPoints.csv" for georeferencing.
    GPS Data: Vertical positions for the AeroPoint targets are determined from the embedded RTK-GPS. The internal theoretical horizontal accuracy is 20 mm. The global horizontal accuracy is calculated using the following equation: global horizontal accuracy (mm) = internal horizontal accuracy (mm) + longest baseline distance (km) * 2. The resultant global horizontal accuracy of Aeropoint positions is 0.055 m.
  4. Where are the gaps in the data? What is missing?
    Lidar data: Data were collected in one flight over Sesuit Marsh with the YellowScan Mapper Plus system. The resulting data included one each of .ys, .lvx, and .T04 scanner data files. These files were used in the creation of the .laz point cloud file, but are not included in this data release. One LPC was produced for the survey area totaling 1207 MB. A digital surface model (DSM) and digital terrain model (DTM) were generated for Sesuit Marsh, totaling 792 MB.
    Aerial Imagery: Gaps in sequential 2-second photo intervals exist where photos were removed from the collection. Photos may have been removed for reasons including collection outside flight plan bounds, poor photo quality, overexposure, or redundancy. The final image count for the YSMP true-color imagery in this data release is 431 images totaling 3722 megabytes (MB). The final image count for the MicaSense Altum-PT is 5898 totaling 53,137 MB. Images were geotagged either manually or by an integrated GPS in the sensor. Image location information is provided in the CSV files titled "2024021FA_Sesuit_Aug2024_aPT_ImageLocs.csv" and "2024021FA_Sesuit_Aug2024_YSMP_ImageLocs.csv".
    Structure-from-motion (SfM) processing: Images that were collected outside the bounds of the flight plan, had poor photoquality, were overexposed, or were redundant were disabled and excluded from the photogrammetric model processing. Only enabled images that were used in the photogrammetric model were included in this data release. Additional Altum-PT calibration photos for radiometric calibration of the reflectance image were included in the data release and are appended with "_cal" at the end of the file name.
    GPS data: 6 AeroPoints were deployed and are included in the "2024021FA_Sesuit_Aug2024_AeroPoints.csv" dataset.
  5. How consistent are the relationships among the observations, including topology?
    UAS data collection: Most missions require multiple flights to complete due to the battery limitations. Between individual flights, the camera/sensor settings and mission plan specifications are not changed to ensure consistent data/imagery collection. Following each flight, data are downloaded to a field computer, copied to an external storage device, and later uploaded to a data server. For lidar data, the RGB photos are verified and the scanner data is plotted in an offline version of YellowScan CloudStation between each flight to verify the scanner was operating as expected and that there are no areas of missing data. Images are also plotted in a photogrammetry software to verify no missing sections of the flight plan before continuing with the mission.
    GPS data: All RTK-GPS rover data were exported as a single tabular CSV file using Microsoft Excel v. 2208. Aeropoint data are uploaded via a WiFi connection to a user defined account on propelleraero.com.The raw data are processed by Propeller and exported to a CSV file.
    Image Data Management: Aerial images were organized into directories labeled by flight number and then transferred to an external drive and later uploaded to the AIMG server. Images were renamed to include the field activity number (FAN), flight number, camera ID, date and time (UTC), and original filename. Gaps in consecutive flight numbers may be due to a variety of reasons, including no photos being collected during a particular flight, failure to initiate camera, or issues with the imagery during a particular flight. Metadata contained in image file headers were modified for all photos to include standard USGS tags. The true-color images from the YellowScan camera module are not internally geotagged and were manually geotagged using the UAS telemetry logs (tlogs). MicaSense Altum-PT images are internally geotagged and by a downwelling light sensor (DLS 2) with integrated u-blox NEO-M8 GNSS module, which also writes illumination information to the image exif. See the processing steps in Lineage for more information.
    All processing was done by members of the Aerial Imaging and Mapping Group (AIMG) at the USGS Woods Hole Coastal and Marine Science Center (WHCMSC).

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints None
Use_Constraints Public domain (CC0-1.0) data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information. These data are not intended for navigational use.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? Aerial imaging and mapping of Sesuit Marsh in Dennis, MA includes one lidar point cloud, two elevation models, one true-color orthomosaics, one multispectral reflectance orthomosaic, associated imagery, and ground control data.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 20-Jun-2025
Metadata author:
Jennifer M. Cramer
U.S. Geological Survey, Northeast Region
Geographer
U.S. Geological Survey
Woods Hole, MA

508-548-8700 x2314 (voice)
whsc_data_contact@usgs.gov
Contact_Instructions:
The metadata contact email address is a generic address in the event the person is no longer with USGS.
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P1EPMT7Y/2024021FA_Sesuit_Aug2024_Metadata.faq.html>
Generated by mp version 2.9.51 on Fri Jun 20 16:05:52 2025