Lidar point cloud, elevation models, GPS data, and imagery and orthomosaics from multispectral and true-color aerial imagery data, collected during UAS operations at Marsh Island, New Bedford, MA on October 26th, 2023

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Frequently anticipated questions:

What does this data set describe?

Title:
Lidar point cloud, elevation models, GPS data, and imagery and orthomosaics from multispectral and true-color aerial imagery data, collected during UAS operations at Marsh Island, New Bedford, MA on October 26th, 2023
Abstract:
Small Uncrewed Aircraft Systems (sUAS) were used to collect aerial remote sensing data over Marsh Island, a salt marsh restoration site along New Bedford Harbor, Massachusetts. Remediation of the site will involve direct hydrological and geochemical monitoring of the system alongside the UAS remote sensing data. On October 26th, 2023, USGS personnel collected natural (RGB) color images, multispectral images, lidar, and ground control points. These data were processed to produce a high resolution lidar point cloud (LPC), digital elevation models (surface and terrain), and natural-color and multispectral reflectance image mosaics. Data collection is related to USGS Field Activity 2023-025-FA and this release only provides the UAS portion.
Supplemental_Information:
For more information about the WHCMSC Field Activity, see https://cmgds.marine.usgs.gov/services/activity.php?fan=2023-025-FA. Images can be viewed or downloaded on the USGS Imagery Data System here https://doi.org/10.5066/P14MGKBY. Note that the bounding coordinates are for the entire area and not individual files.
  1. How might this data set be cited?
    Over, Jin-Si R., and Cramer, Jennifer M., 20241220, Lidar point cloud, elevation models, GPS data, and imagery and orthomosaics from multispectral and true-color aerial imagery data, collected during UAS operations at Marsh Island, New Bedford, MA on October 26th, 2023: data release DOI:10.5066/P19TLXVG, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Over, Jin-Si R., Cramer, Jennifer M., Brosnahan, Sandra M., Ackerman, Seth D., and Ganju, Neil Kamal, 2024, Topographic, multispectral, and GPS data collected during uncrewed aircraft system (UAS) operations at Marsh Island, New Bedford, Massachusetts: data release DOI:10.5066/P19TLXVG, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Over, J.R., Cramer, J.M., Brosnahan, S.M., Ackerman, S.D., and Ganju, N.K., 2024, Topographic, multispectral, and GPS data collected during uncrewed aircraft system (UAS) operations at Marsh Island, New Bedford, Massachusetts: U.S. Geological Survey data release, https://doi.org/10.5066/P19TLXVG.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.91839811
    East_Bounding_Coordinate: -70.91319555
    North_Bounding_Coordinate: 41.65346253
    South_Bounding_Coordinate: 41.64995665
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/66a3d7f1d34ef465b882216d?name=2023-025-FA_MI_data_browse.JPG&allowOpen=true (JPEG)
    Data and products of Marsh Island: multispectral imagery, lidar point cloud, orthos, and DEM.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 26-Oct-2023
    Currentness_Reference:
    Ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: 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?
    2023025FA_MI_ImageryLocations.csv
    The CSV file contains the approximate position of the YSMP and aPT images at the moment of each capture. Note that the positions for each of the six band images is the same, so only the information for one band is provided. (Source: producer defined)
    ImageName
    File names of individual images, see the Process Description for file naming convention. (Source: USGS) Character string.
    GPSDateTime
    Date and UTC time in YYYY:MM:DD HH:MM:ss. (Source: Processor defined) Character string.
    Latitude NAD83[2011]
    Latitude (x) of UAS based on time of each image capture. Positive values represent North coordinates. (Source: USGS)
    Range of values
    Minimum:41.65071944
    Maximum:41.65334400
    Units:decimal degrees
    Longitude NAD83[2011]
    Longitude (y) of UAS based on time of each image capture. Negative values represent West coordinates. (Source: USGS)
    Range of values
    Minimum:-70.91864700
    Maximum:-70.91315000
    Units:decimal degrees
    Altitude NAVD88
    Altitude of the UAS position at the time of each image capture. (Source: None)
    Range of values
    Minimum:12.196
    Maximum:127.596
    Units:meters
    2023025FA_MI_AeroPoints.csv
    Ground control point positions, elevations, and attributes (Source: USGS)
    FAN
    USGS Field Activity Number (Source: USGS)
    ValueDefinition
    2023-025-FAYear, USGS ID, and Field Activity
    Date
    Calendar date of collection (Source: USGS)
    ValueDefinition
    20231026YYYYMMDD
    Point ID
    Unique point identification number. (Source: Processor defined)
    Range of values
    Minimum:1
    Maximum:11
    Attributes
    Unique identifier for ground control points. Prefix AP-### refers to AeroPoint and the last 3 digits of its identifying code. (Source: producer defined) Character string.
    Latitude NAD83[2011]
    Post-processed latitude of AeroPoint position (NAD83[2011]). (Source: USGS)
    Range of values
    Minimum:41.65027441
    Maximum:41.65262461
    Units:decimal degrees
    Longitude NAD83[2011]
    Post-processed longitude of AeroPoint position (NAD83[2011]). (Source: None)
    Range of values
    Minimum:-70.91777486
    Maximum:-70.91403656
    Units:decimal degrees
    Ellipsoid NAD83[2011]
    Post-processed height in meters of AeroPoint in relation to the NAD83(2011) reference ellipsoid. (Source: None)
    Range of values
    Minimum:-27.515
    Maximum:-23.547
    Units:meters
    Northing 19N
    Post-processed interpolated X-coordinate of AeroPoint in NAD83(2011)/UTM Zone 19N. (Source: USGS)
    Range of values
    Minimum:4612721.245
    Maximum:4612978.652
    Units:meters
    Easting 19N
    Post-processed interpolated Y-coordinate of AeroPoint in NAD83(2011)/UTM Zone 19N. (Source: USGS)
    Range of values
    Minimum:340307.590
    Maximum:340618.819
    Units:meters
    Orthometric NAVD88
    Post-processed Z-coordinate of AeroPoint using NAVD88 with Geoid 18 applied. (Source: USGS)
    Range of values
    Minimum:1.647
    Maximum:5.622
    Units:meters
    Xvar mm
    Variance in the X-coordinate from post-processing (Source: producer defined)
    Range of values
    Minimum:2.6
    Maximum:26.6
    Units:millimeters
    Yvar mm
    Variance in the Y-coordinate from post-processing (Source: producer defined)
    Range of values
    Minimum:2.2
    Maximum:13.7
    Units:millimeters
    Zvar mm
    Variance in the Z-coordinate from post-processing (Source: producer defined)
    Range of values
    Minimum:3.2
    Maximum:22.6
    Units:millimeters
    Baseline distance km
    distance of AeroPoint from nearest used processing network base station (Source: Propeller)
    Range of values
    Minimum:0.1
    Maximum:9.6
    Units:kilometers
    2023025FA_MI_YSMP_LPC.laz
    UAS lidar point cloud in .LAZ file format. This georeferenced point cloud was colorized using natural color RGB image values and is not classified. Point density is 347.03 points per square meter and point spacing is 0.054 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:-0.62
    Maximum:26.23
    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
    2023025FA_MI_YSMP_DSM_5cm.tif
    A cloud-optimized digital surface model created from the lidar point cloud with encoded elevation values. Pixel resolution is 5 cm. 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:-0.621
    Maximum:26.231
    Units:meters
    2023025FA_MI_YSMP_DTM_5cm.tif
    A cloud-optimized digital surface model created from the ground points of the classified lidar point cloud with encoded elevation values. Pixel resolution is 5 cm. 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:-0.628
    Maximum:14.662
    Units:meters
    2023025FA_MI_aPT_5Band_Ortho_5cm.tif
    Multispectral (B, G, R, Re, NIR) 32-bit floating point cloud optimized GeoTIFF of Marsh Island. Values have been transformed from digital numbers into reflectance values (unitless). Pixel resolution is 5 cm. No-data value is -32767. (Source: producer defined)
    Band_1
    Blue wavelength band reflectance (Source: Agisoft Metashape)
    Range of values
    Minimum:0.000
    Maximum:2.334
    Units:reflectance
    Band_2
    Green wavelength band reflectance (Source: Agisoft Metashape)
    Range of values
    Minimum:0.000
    Maximum:2.621
    Units:reflectance
    Band_3
    Red wavelength band reflectance (Source: Agisoft Metashape)
    Range of values
    Minimum:0.000
    Maximum:2.589
    Units:reflectance
    Band_4
    Red-edge wavelength band reflectance (Source: Agisoft Metashape)
    Range of values
    Minimum:0.000
    Maximum:3.193
    Units:reflectance
    Band_5
    Near infrared wavelength band reflectance (Source: Agisoft Metashape)
    Range of values
    Minimum:0.000
    Maximum:3.332
    Units:reflectance
    2023025FA_MI_YSMP_RGBavg_Ortho_5cm.tif
    True-color (RGB) cloud optimized GeoTIFF of Marsh Island. (Source: USGS)
    Band_1
    Red wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:255
    Band_2
    Green wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:255
    Band_3
    Blue wavelength band (Source: Agisoft Metashape)
    Range of values
    Minimum:0
    Maximum:255
    Entity_and_Attribute_Overview:
    The filenames are formatted as "2023025FA_MI_sensor/product_resolution.*** ", where 2023025 is the USGS Field activity ID, location is Marsh Island (MI), where sensors are Altum-PT (aPT), YellowScan Mapper Plus (YSMP), AeroPoints and products include orthomosaics (ortho), digital surface and terrain models (DSM and DTM), and lidar point cloud (LPC). The horizontal coordinate reference system for all products is NAD83(2011)/UTM19N, the vertical coordinate reference system (VCRS) is NAVD88 using geoid 18.
    Entity_and_Attribute_Detail_Citation: USGS Field Activity 2023-025-FA

Who produced the data set?

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

    508-548-8700 x2297 (voice)
    jover@usgs.gov

Why was the data set created?

The elevation and imagery products were produced to help the sites conservation partnership evaluate the baseline conditions of the site, with future data collections planned to monitor landscape change from remediation efforts and potential storm impacts.

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: 26-Oct-2023 (process 1 of 6)
    GROUND CONTROL: Eleven AeroPoint GCPs were spaced out over the field site and left on for at least two hours to collect GNSS data. After collection and connected to Wifi, the AeroPoint 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 were exported to a CSV file and named 2023025FA_MI_AeroPoints.csv.
    Date: 26-Oct-2023 (process 2 of 6)
    UAS FLIGHTS: The lidar sensor is a 905 nm wavelength Livox Avia with a 70.4/ 4.5 degree horizontal and vertical field of view (FOV). The lidar scanner has two scan pattern options, repetitive and non-repetitive. The repetitive scan pattern moves the sensor linearly along the primary axis and is optimal for unvegetated areas. The non-repetitive scan pattern moves the sensor in spirograph (flower) motion and, though less accurate than the repetitive scan pattern, is optimal for vegetated areas as it can capture more angles by surveying in front and behind the sensor. The camera module is a SONY UMC - 10RC, a 20.4 megapixel (MP). The system also consists of a Trimble AV18 GNSS antenna mounted to the top of the UAS and connected to the lidar system via GNSS cable. The lidar data is 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 micro SD card as *.jpeg files. A configuration text file (CONFIG.TXT) is pre-loaded onto the USB thumb drive and can be edited to control lidar and camera module settings, including the camera triggering height, the camera triggering interval, and the lidar scan pattern.
    The Altum-PT has 7 sensors with global shutters: 5 multispectral bands, blue (443-507 nm), green (533-587 nm), red (652-684 nm), red edge (705-729 nm), and near-infrared (NIR) (785-899 nm), 1 panchromatic band (171.5 nm - 1098 nm), and 1 long-wave infrared (LWIR) thermal band (4.5 - 16.5 microns). The LWIR band images were not used in any processing workflows and were excluded from this data release. The multispectral bands have a focal length of 8 mm and acquires images at 3.2 megapixels, 2064 x 1544 pixel resolution, and a 12-bit depth. The panchromatic band has a focal length of 16.3 mm and acquires images at 12 megapixels, 4112 x 3008 pixel resolution, and 12-bit depth. The sensor apertures are f/1.8 for the spectral bands, f/4.5 for the panchromatic band, and f/1.1 for the LWIR thermal band. Sensor properties are automatically written to the image exif. Images are saved to a CF Express type B SD card in TIFF format. *Note that because most 3rd-party software supports 16-bit images, the 12-bit images are output to TIFF files in a 16-bit container with the last four bits filled with zeros. Both sensors (YSMP and aPT) were attached to an DJI Matrice 600 Pro UAS with approved government edition firmware. Two 1x1 m Group 8 Technology reflectance calibration tarps with reflectance values of 0.48 and 0.12 were staked out within the UAS survey area for validation of post-processed aPT reflectance products. The YSMP lidar data was collected with the UAS flying at 5 m/s at 100 meters above ground level with north-south and east-west transect passes. The scan method was set to repetitive. The camera module was set to take images every 2 seconds. After the flight the lidar data were taken off the sensor. The aPT data was collected with the UAS flying at 8 m/s at 100 meters above ground level with north-south and east-west transect passes that achieve ~80% forelap and sidelap. Image sets were taken every 2 seconds. The Altum-PT received power from a connection to the UAS. The downwelling light sensor was attached and measured ambient light for each of the spectral bands captured by the camera. For each camera shutter trigger, camera settings (focal length, ISO, etc), spectral irradiance, roll, pitch, yaw, gain, exposure time, and GPS position data were automatically incorporated into the Exif data for each image. Just prior to takeoff and landing, a Micasense calibration panel (RP06-2224002-OB) was placed under the camera for several seconds to capture calibration images. After the flight, the UAS was powered off, the SD card was removed, and all images and files relating to the survey were downloaded to a field computer. Note, the Altum-PT geotagged positions embedded in the exif information are in WGS84 and Geoid EGM96 and for the YSMP photos its WGS84 and ellipsoid height, this is how the data are collected. The positions have been converted to NAD83(2011) and NAVD88 geoid 18 in the imagery locations file (2023025FA_MI_ImageryLocations.csv) and is accounted for when transforming to NAD83(2011)/UTM19N and NAVD88 Geoid 18 in the products.
    Date: 20-Jul-2024 (process 3 of 6)
    LIDAR DATA: The YSMP lidar data were processed in YellowScan CloudStation software integrated with Trimble POSPac UAV 9.0. Base station GNSS data were downloaded from CORS station MADA (https://geodesy.noaa.gov/UFCORS/) for the time the UAS was flying. Raw scanner data (.ys file) was imported into YellowScan CloudStation, the sensor (.profile) and camera (.camera) profiles, provided by the vendor, were selected for the project and the project coordinate reference system is set. CloudStation flight trajectories are adjusted manually to select the desired data to be processed. The .T04 file and base station GNSS rinex file were used to correct and optimize the sensor position trajectories 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 classified in CloudStation using a bare-ground classification scheme (0-Created, never classified; 2-Ground) with the settings Object inner size = 55 m, Steepness = 0.05 m, minimal object height = 0.50 m, and a point cloud thickness of 0.15 m. The LPC was colored by the YSMP camera based on the photo timestamp. The classified LPC is used to export a DTM of the mean values of just the classified ground points (2023025FA_MI_YSMP_DTM_5cm.tif). The classification is then cleared in Global Mapper (v 26.0) so all points are unclassified. Points are also deleted in Global Mapper that are interpreted to be noise or are above a reasonable elevation threshold based on the surrounding features. The clean LPC is exported as a zipped laz file (v 1.4) (2024004FA_MI_Apr_YSMP_LPC.laz). A DSM using maximum values of all points is exported (2023025FA_MI_YSMP_DSM_5cm.tif). All files were exported in EPSG:6348 (NAD83(2011)/UTM zone 19N and the vertical datum in EPSG:5703 (NAVD88 height in meters).
    Date: 20-Jul-2024 (process 4 of 6)
    RAW IMAGERY: The aPT images are automatically geotagged from the UAS GPS, the YSMP images were geotagged in Emlid Studio using the lidar .T04 file and MADA base rinex files. Both the aPT and YSMP images were processed to add additional information required by the USGS to the EXIF headers using ExifTools (https://exiftool.org/, version: 12.06), and the files were renamed to a unique identifier using Namexif (http://www.digicamsoft.com/softnamexif.html, version 2.1) to avoid any possibility of duplicate names. These steps are described here. Note that in the commands below .*JPG was used for YSMP images and *.tif was used for the aPT images) 1. ExifTools was used to tag each photo headers following the Imagery Data System EXIF Guidance. Attributes (e.g. Credit, Copyright, UsageTerms, ImageDescription, Artist, etc) were stored in a csv file and written to each image with the command:' exiftool -csv="C:\directory\name\EXIF.csv" C:\directory\name\of\photos *.JPG ' To read out the photo information to a csv when in the directory with the photos the command is: exiftool -csv *.JPG > directory/name/allheaders_out.csv 2. All the images were renamed with Namexif (https://us.digicamsoft.com/softnamexif.html v 2.2 accessed April 2020) to ensure unique filenames and compliance with the USGS Coastal and Marine Hazards and Resources Program's best practices for image naming convention. Images were renamed with the field survey ID prefix; flight number, and ID that distinguishes USGS cameras by make/camera number, the image acquisition date, coordinated universal time (UTC) in ISO8601 format, and a suffix with the original image name. For example, image name '2023025FA_f01YSMP_20231026T165822Z_IMG_####_#', 2023025FA is the field activity ID, f01 is the flight number, YSMP is the camera on the YellowScan Mapper Plus and aPT is the altum-PT, 20231026 is the UTC date in the format YYYYMMDD, and a 'T' is used to separate UTC date from UTC time in format HHMMSS followed by a Z. The IMG_####_# is the original raw photo name appended to the end of the new filename; for the aPT there are images with the same time and photo name distinguished by the band number _#.
    Date: Jun-2024 (process 5 of 6)
    PHOTOGRAMMETRY: The two ortho products were created in Agisoft Metashape v. 2.0.1 using the following general steps (see Over and others, 2021 for a more detailed SfM methodology explanation, https://support.micasense.com/hc/en-us/articles/4416696717847-Pan-sharpening-processing-data-from-Altum-PT-and-RedEdge-P-cameras-in-Agisoft-Metashape for processing the aPT images, and https://support.skydio.com/hc/en-us/articles/27236378437019-Scan-reconstruction-best-practices-with-Skydio-X10 for processing the SX10 images): 1. For each sensor (YSMP and aPT) a project was created and imagery was imported. 2. Photos were aligned at a low accuracy and then GCPs were automatically detected in the point cloud. For the aPT images, the Panchromatic band images were used to identify tie points. GCP positions (2023025FA_MI_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 0.01/0.02 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 12, one iteration of the 'Projection accuracy' filter at a level of 3, and three 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 independent high quality dense clouds with a low-frequency filtering algorithm could be made from the YSMP and aPT images. The dense point clouds were 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 YSMP orthomosaic is a 3-band RGB-averaged orthomosaic exported at 5 cm resolution (2023025FA_MI_RGBavg_5cm.tif). The aPT ortho product was transformed so that the bands were all divided by the reflectance normalization factor 32768 (half of the available digital number range or 100% reflectance for each band for 16-bit images). The normalization process produces values that are a unitless reflectance value between 0 and 1, where 1 would be 100% reflectance, i.e. lighter. This 5-band product was exported at 5 cm resolution (2023025FA_MI_aPT_5band_Ortho_5cm.tif).
    Date: 30-Jul-2024 (process 6 of 6)
    CLOUD OPTIMIZATION: All geoTIFF products were DEFLATE compressed and turned into a cloud-optimized GeoTIFFs (COG) using 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:
    Jin-Si R. Over
    U.S. Geological Survey, Woods Hole Coastal and Marine Science Center
    Geographer
    U.S. Geological Survey
    Woods Hole, MA

    508-548-8700 x2297 (voice)
    jover@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?
    The horizontal and vertical accuracy of the products (2023025FA_MI_YSMP_LPC.laz, 2023025FA_MI_YSMP_DSM_5cm.tif, 2023025FA_MI_YSMP_DTM_5cm.tif, 2023025FA_MI_YSMP_RGBavg_5cm.tif, 2023025FA_MI_aPT_5Band_Ortho_5cm.tif) were assessed using the AeroPoint ground control points (GCPs). It should also be noted that accuracy estimates of the products are for areas of bare ground or low vegetation where GCPs were placed. Lidar and lidar products do not have data where water was present. The spectral accuracy of the multispectral 5-band ortho product was determined by comparing the reflective value of two reflectance calibration tarps that are visible in the imagery to their established value. The two radiometrically calibrated reflective tarps visible in the ortho image have known values of 0.48 (light) and 0.12 (dark). The average value of each tarp was evaluated by extracting all the values for each band within the area of each tarp in the 5-band products. The average values of the light tarp, from band 1 to 5, were 0.422, 0.473, 0.468, 0.457, 0.443. The average values of the dark tarp, from band 1 to 5, were 0.138, 0.132, 0.121, 0.121, and 0.117. The RGB orthoimage produced by the YSMP imagery was not checked in this manner. Additional sources of error, such as moving objects, may cause accuracy estimates to exceed estimates in localized portions of the products. The accuracy of the lidar classification that produced the digital terrain model (DTM) was not assessed, users are advised to do their own quality control. Misclassification may cause gaps in the DTM.
  2. How accurate are the geographic locations?
    The aPT xy information was acquired from an internal GPS receiver and has an average horizontal accuracy of 0.88 meters; individual image xy accuracies are embedded in the exif information. The YSMP images were geotagged with the post-processed lidar .T04 file and base station data and have an average xy accuracy of 0.02 m. The lidar point cloud, and by association the DSM and DTM, horizontal accuracy was assessed against positions of the AeroPoints and the USGS 3DEP stable structures such as buildings, and the photogrammetry orthomosaics. The horizontal accuracy is variable and within 20 cm. The orthomosaics were spatially georeferenced using AeroPoints and created using photogrammetry. The 11 GCPs were used as control points during SfM photogrammetry processing, where the horizontal root mean square error (RMSE) of the check points as reported from the Metashape projects are xy 0.024/0.015 m.
  3. How accurate are the heights or depths?
    The aPT z information was acquired from an internal GPS receiver and has an average vertical accuracy of 1.50 meters; individual image z accuracies are embedded in the exif information. The YSMP images were geotagged with the post-processed lidar T04 file and base station data and have an average z accuracy of 0.02 m. The lidar point cloud was assessed against the USGS 3DEP surface, and the vertical difference is within 10 cm. The lidar based digital surface model was assessed against the elevations of the AeroPoints, and the RMSE (n=10) was 0.04 m. The lidar based DTM was not vertically assessed due to the subjectivity of the classification. The orthomosaics do not have a vertical component.
  4. Where are the gaps in the data? What is missing?
    Imagery: Once turned on the aPT and YSMP cameras triggered every 2 seconds. The aPT took 7 individual images each time, distinguished by a suffix of _1 to _7. All images with a suffix of _7 were removed from this dataset; these are the thermal (LWIR) images that did not have a calibration check source nor are relevant to the goals of the field activity. One to five sets of the MicaSense Calibration panel at the beginning and end of each flight were kept and given the suffix _calib, but additional sets of images were removed for redundancy and space. Images at take-off and landing for the aPT and YSMP were also removed for space. All of these removed images can account for the non-consecutive original file names and results in a total of 3,996 aPT images and 350 YSMP images. Products: GeoTIFF products are cloud-optimized. One AeroPoint is not within the extent of the lidar products.
  5. How consistent are the relationships among the observations, including topology?
    There were two M600 UAS flights and eleven AeroPoint GCPs. The first flight (26 min) used the micasense altum-PT (aPT) to collect multispectral imagery (7-bands) and was used to produce the 5-band orthomosaic. The second flight (14 min) used the YellowScan Mapper+ (YSMP) to collect lidar data and RGB images and produced the lidar point cloud (LPC), digital terrain model (DTM), digital surface model (DSM), and the true-color (RGBavg) orthomosaic. All data fall into expected elevation ranges of a low-lying coastal marsh.

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 Marsh Island includes the Altum-PT imagery and multispectral orthomosaic, the YellowScan Mapper Plus lidar point cloud, elevation models, imagery and true-color orthomosaic, and AeroPoint ground control points.
  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. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Not for navigational use.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 20-Dec-2024
Metadata author:
Jin-Si R. Over
U.S. Geological Survey, Northeast Region
Geographer
U.S. Geological Survey
Woods Hole, MA

508-548-8700 x2297 (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_P19TLXVG/2023025FA_MI_meta.faq.html>
Generated by mp version 2.9.51 on Fri Dec 20 15:45:42 2024