Time Series of Structure-from-Motion Products - Point Clouds: Little Dauphin Island and Pelican Island, Alabama, September 2018 to April 2019

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How might this data set be cited?
   Kranenburg, Christine J., Brown, Jenna A., Bosse, Stephen T., and Dalyander, P. Soupy, 20210610, Time Series of Structure-from-Motion Products - Point Clouds: Little Dauphin Island and Pelican Island, Alabama, September 2018 to April 2019: U.S. Geological Survey Data Release doi:10.5066/P9I6BP66, U.S. Geological Survey, St. Petersburg, Florida.

   Online Links:

   • https://doi.org/10.5066/P9I6BP66

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -88.12889537
   East_Bounding_Coordinate: -88.10731142
   North_Bounding_Coordinate: 30.28187897
   South_Bounding_Coordinate: 30.23092080
   

3. What does it look like?
4. Does the data set describe conditions during a particular time period?

   Calendar_Date: 12-Sep-2018

   Currentness_Reference:

   ground condition

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: vector digital data
   

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point
   2. What coordinate system is used to represent geographic features?
      

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:

      UTM_Zone_Number: 16N
      Transverse_Mercator:

      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -87
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0
      

      Planar coordinates are encoded using coordinate pair
      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.
      The ellipsoid used is Geodetic Reference System 80.
      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?

   yyyy-mm-IslandName-ptcloud.laz

   Compressed LAS version 1.2 file, in .laz format, containing topographic elevation point cloud data for each survey. Points are unclassified. The point cloud files are named with the following convention: yyyy-mm-Islandname-ptcloud.laz, where ‘yyyy-mm’ represents the survey date as year (yyyy) and month (mm); ‘IslandName’ can have a value of either LittleDauphinIsland (Little Dauphin Island, AL) or PelicanIsland (Pelican Island, AL); and ‘ptcloud’ is used to designate the dataset as a point cloud. (Source: U.S. Geological Survey)

   X

   Easting in meters (Source: NAD83 (2011), UTM Zone 16N) Varying value range

   Y

   Northing in meters (Source: NAD83 (2011), UTM Zone 16N) Varying value range

   Z

   Altitude in meters (Source: NAVD88, orthometric height) Varying value range

   Entity_and_Attribute_Overview:

   The point cloud data are exported as a compressed LAS file, with a .laz file extension. This file consists of topography elevation data available for each survey. Data were generated from aerial photographs using Agisoft Photoscan software. The photogrammetry process was controlled through application of GCPs. Points are unclassified.

   Entity_and_Attribute_Detail_Citation: U.S. Geological Survey
   

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Christine J. Kranenburg
   • Jenna A. Brown
   • Stephen T. Bosse
   • P. Soupy Dalyander
2. Who also contributed to the data set?

   Data collection was funded by the U.S. Geological Survey. We would like to thank the following people for their contribution to the data collection efforts: Nicholas Enwright, Brett Patton, Chelsea Stalk, Nancy DeWitt and Sara Zeigler of the USGS, and Spencer Stelly of Stelly Consulting.

3. To whom should users address questions about the data?
   Christine J. Kranenburg

   U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

   600 4th Street South

   St. Petersburg, FL
   

   USA

   727-502-8000 (voice)

   ckranenburg@usgs.gov

Why was the data set created?

These SfM products were produced from aerial images collected at Little Dauphin and Pelican Islands, Alabama, from September 2018 to April 2019, in order to develop integrated models linking geomorphology, habitat characteristics, and non-breeding shorebird species usage.

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: 27-Aug-2019 (process 1 of 1)

   The SfM products were created for each UAS survey date individually, using the RGB digital negative (DNG) photos (Kranenburg and others, 2021). The complete set of photos was imported into Agisoft Photoscan (versions 1.3.5 - 1.5.5), along with corresponding GCP reference information, and each flight was put into separate camera calibration groups. Photos were aligned at high accuracy, with a keypoint limit of 50,000 and unlimited tiepoints. Camera positions and the lens model were refined using three statistical metrics: reconstruction uncertainty, projection accuracy, and reprojection error with threshold values of 10, 2.6-3.0, and 0.3 respectively. Once the photo positions and lens models were optimized, dense point clouds were generated with Photoscan (Goncalves and Henriques, 2015) using the high quality and moderate filtering settings. Person who carried out this activity:
   

   Christine J. Kranenburg

   U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

   Cartographer

   600 4th Street South

   St. Petersburg, FL
   

   USA

   727-502-8000 (voice)

   ckranenburg@usgs.gov

3. What similar or related data should the user be aware of?
   Kranenburg, C.J., Brown, J.A., Sturdivant, E.J., Stalk, C.A., Pendleton, E.A., and Ackerman, S.D., 2021, Time Series of True Color Aerial Imagery from Small Unmanned Aircraft Systems: Little Dauphin Island & Pelican Island, Alabama, September 2018 – April 2019: U.S. Geological Survey Data Release Unknown.

   Online Links:

   • Unknown

   Goncalves, J.A., and Henriques, R., 2015, UAV photogrammetry for topographic monitoring of coastal areas: ISPRS Journal of Photogrammetry and Remote Sensing vol. 104.

   Online Links:

   • https://doi.org/10.1016/j.isprsjprs.2015.02.009

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

1. How well have the observations been checked?
   Point cloud data are provided in American Society for Photogrammetry and Remote Sensing (ASPRS) lidar classified laser (LAS) format, (version 1.2). Header and point attributes for the LAS files can be found on the ASPRS website at, https://www.asprs.org/wp-content/uploads/2010/12/asprs_las_format_v12.pdf. The horizontal and vertical measurements of the surface models were compared against global positioning system measurements of fixed features covered by the survey.
2. How accurate are the geographic locations?
   The SfM-based geospatial products have an overall horizontal root-mean-square error (RMSE) of 3.4 cm, determined by comparing the horizontal position of the surveyed temporary check points (4-square, black and white, checkerboard targets) and the corresponding horizontal positions digitized in the orthomosaic, for all surveys.
3. How accurate are the heights or depths?
   The SfM-based geospatial products have an overall vertical root-mean-square error (RMSE) of 3.3 cm, determined by comparing the surveyed check point elevations and the corresponding elevations in the DEM, for all check points from all surveys.
4. Where are the gaps in the data? What is missing?
   This dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
5. How consistent are the relationships among the observations, including topology?
   All data fall within expected ranges, except points near and offshore of the waterline and in internal lagoons. Data in the point cloud near the waterline and over water bodies can be noisy and may result in erroneous measurements in the point cloud.

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:

USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator of the dataset and in products derived from these data.

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

   Attn: SPCMSC Data Management Group

   600 4th Street South

   St. Petersburg, FL
   

   USA

   727-502-8000 (voice)

   gs-g-spcmsc_data_inquiries@usgs.gov
2. What's the catalog number I need to order this data set? These data are available in compressed LAS format contained in a single ZIP file of SfM products per UAS survey. The point cloud files are named with the following convention: yyyy-mm-Islandname-ptcloud.laz where yyyy-mm represents the survey date as year (yyyy) and month (mm); IslandName can have a value of either LittleDauphinIsland or PelicanIsland.
3. What legal disclaimers am I supposed to read?

   This publication was prepared by an agency of the United States Government. Although these data were processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:

     The .zip file contains SfM products per UAS survey, including the point cloud data saved as a .laz file. in format LAZ

     Network links:

     https://coastal.er.usgs.gov/data-release/doi-P9I6BP66/data/201809_PelicanIsland_SfMProducts.zip https://coastal.er.usgs.gov/data-release/doi-P9I6BP66/data/201811_PelicanIsland_SfMProducts.zip https://coastal.er.usgs.gov/data-release/doi-P9I6BP66/data/201812_PelicanIsland_SfMProducts.zip https://coastal.er.usgs.gov/data-release/doi-P9I6BP66/data/201902_PelicanIsland_SfMProducts.zip https://coastal.er.usgs.gov/data-release/doi-P9I6BP66/data/201904_PelicanIsland_SfMProducts.zip https://coastal.er.usgs.gov/data-release/doi-P9I6BP66/data/201812_LittleDauphinIsland_SfMProducts.zip https://coastal.er.usgs.gov/data-release/doi-P9I6BP66/data/201903_LittleDauphinIsland_SfMProducts.zip

   • Cost to order the data: None.

Who wrote the metadata?

Dates:

Last modified: 24-May-2021

Metadata author:

Christine J. Kranenburg

U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center

Cartographer

600 4th Street South

St. Petersburg, FL

USA

727-502-8000 (voice)

ckranenburg@usgs.gov

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)