Greig Street point cloud from low-altitude aerial imagery from unmanned aerial systems (UAS) flights over of the Lake Ontario shoreline in the vicinity of Sodus Bay, New York in July 2017 (LAZ file)

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What does this data set describe?

Title:
Greig Street point cloud from low-altitude aerial imagery from unmanned aerial systems (UAS) flights over of the Lake Ontario shoreline in the vicinity of Sodus Bay, New York in July 2017 (LAZ file)
Abstract:
Low-altitude (80-100 meters above ground level) digital images were obtained from a camera mounted on a 3DR Solo quadcopter, a small unmanned aerial system (UAS), along the Lake Ontario shoreline in New York during July 2017. These data were collected to document and monitor effects of high lake levels, including shoreline erosion, inundation, and property damage in the vicinity of Sodus Bay, New York. This data release includes images tagged with locations determined from the UAS GPS; tables with updated estimates of camera positions and attitudes based on the photogrammetric reconstruction; tables listing locations of the base stations, ground control points, and transect points; geolocated, RGB-colored point clouds; orthomosaic images; and digital elevation models for each of the survey regions. Collection of these data was supported by the Federal Emergency Management Agency, the State of New York Departments of State and Environmental Conservation, and the USGS Coastal and Marine Geology Program and was conducted under USGS field activity number 2017-042-FA.
Supplemental_Information:
For more information about this field activity, see https://cmgds.marine.usgs.gov/fan_info.php?fan=2017-042-FA.
  1. How might this data set be cited?
    U.S. Geological Survey, 2018, Greig Street point cloud from low-altitude aerial imagery from unmanned aerial systems (UAS) flights over of the Lake Ontario shoreline in the vicinity of Sodus Bay, New York in July 2017 (LAZ file): data release DOI:10.5066/P9XQYCD0, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Sherwood, Christopher R., Brosnahan, Sandra M., Ackerman, Seth D., Borden, Jonathan, Montgomery, Ellyn T., Pendleton, Elizabeth A., and Sturdivant, Emily J., 2018, Aerial imagery and photogrammetric products from unmanned aerial systems (UAS) flights over the Lake Ontario shoreline at Sodus Bay, New York, July 12 to 14, 2017.: data release DOI:10.5066/P9XQYCD0, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Sherwood, C.R., Brosnahan, S.M., Ackerman, S.D., Borden, Jonathan, Montgomery, E.T., Pendleton, E.A., and Sturdivant, E.J., 2018, Aerial imagery and photogrammetric products from unmanned aerial systems (UAS) flights over the Lake Ontario shoreline at Sodus Bay, New York, July 12 to 14, 2017: U.S. Geological Survey data release, https://doi.org/10.5066/P9XQYCD0.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -76.986433
    East_Bounding_Coordinate: -76.969400
    North_Bounding_Coordinate: 43.273290
    South_Bounding_Coordinate: 43.265003
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5b1ee15be4b092d965254a53/?name=2017042FA_GreigSt_PointCloud_browse.jpg (JPEG)
    Browse image of a portion of the point cloud generated from photogrammetry and low-altitude aerial images obtained with unmanned aerial systems (UAS).
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 14-Jul-2017
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: LAZ binary 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 (252,454,437)
    2. What coordinate system is used to represent geographic features?
      The map projection used is Universal Transverse Mercator.
      Projection parameters:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -75.00000
      Latitude_of_Projection_Origin: 0.000
      False_Easting: 500000.0000
      False_Northing: 0.0000
      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 6378137.000000.
      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 (NAVD88)
      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?
    Entity_and_Attribute_Overview:
    The attribute information associated with point cloud follows the LAZ file standard. Attributes include location (northing, easting, and elevation in the NAD83/UTM zone 18N (EPSG::26918) horizontal and NAVD88 vertical coordinate systems), color (red, blue, and green components), intensity, and classification. All points are classified as 0 (unclassified).
    Entity_and_Attribute_Detail_Citation:

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Sandra Brosnahan
    Physical Scientist
    384 Woods Hole Road
    Woods Hole, Massachusetts

    508-548-8700 x2265 (voice)
    508-457-2310 (FAX)
    sbrosnahan@usgs.gov

Why was the data set created?

These points provide the calculated XYZ (horizontal and vertical) coordinates and RGB (red-green-blue) values of the land surface during a mid-day low-tide on 14 July, 2017 in the Greig Street study area. The product was created to demonstrate the use of structure-from-motion (SfM) for coastal research and may be used to develop further datasets, such as the digital elevation models, geomorphic feature mapping, and land cover classification.

How was the data set created?

  1. From what previous works were the data drawn?
    geotagged images (source 1 of 2)
    U.S. Geological Survey, unpublished material, Field geotagged aerial imagery (or whatever title you want).

    Type_of_Source_Media: raster digital images
    Source_Contribution:
    These are the images geotagged in the field and used to produce the subsequent photogrammetric products. The images available from the larger work citation of this data release have updated geotag information.
    GCPs (source 2 of 2)
    U.S. Geological Survey, 2018, Ground control point and transect locations associated with images collected during unmanned aerial systems (UAS) flights over The Lake Ontario shoreline in the vicinity of Sodus Bay, New York in July 2017.

    Other_Citation_Details:
    available from the Larger Work citation of this dataset (Suggested citation: Sherwood, C.R., Brosnahan, S.M., Ackerman, S.D., Borden, Jonathan, Montgomery, E.T., Pendleton, E.A., and Sturdivant, E.J., 2018, Aerial imagery and photogrammetric products from unmanned aerial systems (UAS) flights over the Lake Ontario shoreline at Sodus Bay, New York, July 12 to 14, 2017: U.S. Geological Survey data release, https://doi.org/10.5066/P9XQYCD0.)
    Type_of_Source_Media: text data files
    Source_Contribution:
    The ground control points (GCPs; not transect points -- see metadata for more information) were used to geolocate the photogrammetric products
  2. How were the data generated, processed, and modified?
    Date: Sep-2017 (process 1 of 2)
    Images imported into Photoscan (Agisoft Photoscan Professional v. 1.3.2) for the Lake Ontario projects were geotagged using Mission Planner Software (version 1.3.49). Point Clouds for the Lake Ontario projects were constructed using photogrammetry software (Agisoft Photoscan Professional v. 1.3.2) and digital images taken approximately 80 and 100 m above the ground on July 10 - 14, 2017, with a Ricoh GRII digital camera mounted in a 3DR Solo quadcopter operated the U.S. Geological Survey. This point cloud is the product from one of several photogrammetry projects from field activity 2017-042-FA. Four projects were used for flights in the vicinity of Sodus Bay on July 12, 13, and 14, 2017 (Lake Bluffs, Charles Point, Sodus North, and Greig Street). The projects combined images with ground control points to produce geolocated, colored (red-green-blue schema) point clouds. This point cloud, for the Lake Bluffs project, was created using a standard processing flow as described in the processing step below. Person who carried out this activity:
    U.S. Geological Survey, Woods Hole Coastal and Marine Science Center
    Attn: Christopher R. Sherwood
    Research Oceanographer
    384 Woods Hole Road
    Woods Hole, Massachusetts
    U.S.A.

    508-548-8700 x2269 (voice)
    508 457 2310 (FAX)
    csherwood@usgs.gov
    Date: 13-Sep-2017 (process 2 of 2)
    The following steps make up the processing flow for creating this point cloud:
    1. Geotagged images (see source citation) containing useful imagery from the survey area were imported into Agisoft Photoscan Professional v. 1.3.2 software using the “Add photos…” tool. Photos taken before and immediately after takeoff, photos taken immediately prior to and after landing, and photos with 100% water were not loaded into the project. Project coordinate system is set to EPSG::7660 WGS84 (G1150) geocentric coordinate system.
    2. Using ”Convert”, the coordinate system of the images (called “cameras” in Photoscan) was converted from native latitude/longitude WGS84 (G1150) coordinate system to meters in NAD83/UTM zone 18N (EPSG::26918).
    3. The photos were processed through an initial alignment and optimization procedure using the following settings: Alignment - Accuracy: “High”; Pair selection: “Reference”; Key point limit: 80,000; Tie point limit; 0 (unlimited). Adaptive camera model fitting option was selected. Optimization - Lens-calibration parameters f, cx, cy, k1, k2, k3, p1, and p2 were included; b1, b2, and higher-order parameters k4, p3, and p4 were not.
    4. The sparse point cloud (also known as tie points; created as a result of photo alignment and optimization) was edited using an iterative error-reduction procedure to filter the data. This was done in several iterations of a process called "Gradual Selection" to first to reduce reconstruction uncertainty (to a unitless value of 10) and then projection accuracy (to a weighted value of 3).
    5. Ground control points were created by first by letting the software automatically detect markers where it finds all of the 4-ft square black/white targets deployed (false targets that are sometimes detected were manually deleted). The automatically-generated marker labels were manually changed to match the names in the survey notes and GCP location files.
    6. "Import markers” was used to load the GCP location files, which assigned coordinates (northing, easting, and elevation in UTM Zone 18 North meters in NAD83 and NAVD88 coordinate systems) from the location file to the detected markers. The locations of auto-detected markers were retained.
    7. Another round of "Gradual Selection" was done to reduce the reprojection error (to a value of 0.3 pixels, unless more than 10% of the points would be removed).
    8. A dense point cloud was then created with the parameters "High" quality and “Aggressive” depth filtering.
    9. The dense point cloud was exported in LAZ format (2017-07-10_GreigSt_POINTS.laz) and was then both were renamed to the AIM data release filenaming standard (e.g. 2017042FA_GreigSt_PointCloud.laz). Person who carried out this activity:
    U. S. Geological Survey, Woods Hole Coastal and Marine Science Center
    Attn: Christopher R. Sherwood
    Research Oceanographer
    384 Woods Hole Road
    Woods Hole, Massachusetts
    U.S.A.

    508-548-8700 x2269 (voice)
    508 457 2310 (FAX)
    csherwood@usgs.gov
  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?
    Horizontal positions of individual points for the point cloud were calculated by photogrammetric software and ground control points. There are several sources of potential error that affect the horizontal accuracy:
    1. The horizontal error estimate provided by Agisoft Photoscan for the Greig Street project as a result of alignment, optimization, and ground control processing procedures is 9.91 cm. This value is an RMS estimate of positional error at discrete locations within the orthomosaic.
    2. Ground control points were collected using a Spectra model SP80 GNSS receiver set to record XY locations with the national adjustment of 2011 (NAD83(2011) UTM zone 18N EPSG::6347), which differs from the Photoscan project coordinate system (NAD83/UTM zone 18N (EPSG::26918)). This difference may introduce an average additional 0.9 cm horizontally at the 95% confidence level according to the National Geodetic Survey (https://www.ngs.noaa.gov/web/surveys/NA2011/).
    3. Additionally, an assessment of repeated survey sites including transect points and ground control points, using the same equipment by the USGS Aerial Imagery and Mapping (AIM) group estimates an accuracy of the ground control point locations of 1.76 cm (horizontal) and 0.54 cm (vertical).
    The combination of the potential horizontal error is on the order of 12.35 cm for the Greig Street products. Although some portions of the map may contain much larger errors, greater than 2 m horizontally, especially along the boundary of the project that are far from a ground control point, and across water bodies. The horizontal coordinate system for the Charles Point Point Cloud, DEM and Orthomosaic is NAD83/UTM zone 18N (EPSG::26918).
    It is also important to note: The UAS image locations are derived from a mRo GPS (u-Blox Neo-M8N / 3DR SOLO Upgrade), located on the UAS, which receives signals from GPS and GLONASS satellites in WGS84 (G1150) EPSG::7660. This location information is used by the Photoscan software to help with the initial alignment, however after photo alignment, these location data have no bearing on the project or the derivative product. Therefore the positional accuracy and potential errors of the GPS data attached to the input photographs is not propagated to the Photoscan project and therefore does not contribute to the overall horizontal accuracy of the products (Point Cloud, DEM and Orthomosaic).
  3. How accurate are the heights or depths?
    Vertical positions of individual points for the point cloud were calculated by photogrammetric software and ground control points. There are several sources of potential error that affect the vertical accuracy:
    1. The vertical error estimate provided by Agisoft Photoscan for the Greig Street project as a result of alignment, optimization, and ground control processing procedures is 7.23 cm. This value is an RMS estimate of positional error at discrete locations within the orthomosaic.
    2. Ground control points were collected using a Spectra model SP80 GNSS receiver that was receiving real-time differential corrections from a GNSS base station established in Sodus Bay NY. The Z heights were reference to the NAVD88 vertical datum. An assessment of repeated survey sites using the same equipment by the USGS Aerial Imagery and Mapping group estimates a potential accuracy error of the ground control point locations of 1.76 cm (horizontally) and 0.54 cm (vertically).
    The combination of the potential vertical error is on the order of 2.0 cm for the photogrammetric products. Although some portions of the map may contain much larger errors, greater than 20 m vertically, especially along the boundary of the project that are far from a ground control point, and across water bodies. The vertical datum for the Greig Street Point Cloud, DEM and Orthomosaic is NAVD88 (meters).
    It is also important to note: The UAS image locations are derived from a mRo GPS (u-Blox Neo-M8N / 3DR SOLO Upgrade), located on the UAS, which receives signals from GPS and GLONASS satellites in WGS84 (G1150) EPSG::7660. This location information is used by the Photoscan software to help with the initial alignment, however after photo alignment, these location data have no bearing on the project or the derivative product. Therefore the positional accuracy and potential errors of the GPS data attached to the input photographs is not propagated to the Photoscan project and therefore does not contribute to the overall vertical accuracy of the products (Point Cloud and DEM).
  4. Where are the gaps in the data? What is missing?
    This point cloud was constructed from 1235 of the 1640 loaded images from successful flights over the Greig Street survey area that were imported into the Greig Street photogrammetry project. Some images were eliminated automatically by the Agisoft Photoscan software during processing because they contained insufficient numbers of reliable tie points relating them to ground features visible in adjacent images. Many of the eliminated images contain views of mostly water or oblique views that included the horizon. All of the points generated by the software to form a dense cloud have been included in this data release. That includes points that likely do not represent ground features, but are instead artifacts generated by moving water surfaces and or erroneous tie points. These points are commonly eliminated through either automatic or manual classification, but have been retained to allow experimentation with point classification methods. The fully processed Photoscan project for Greig Street (used to create the subsequent DEM and orthomosaic) used 1235 of the original 1640 images and the dense point cloud contains more than 252 million points.
  5. How consistent are the relationships among the observations, including topology?
    Coordinates recorded for each point describe discrete positions in space and the visual reflectance at the time of capture. Photoscan software determines the photos used in the construction of the products (Point Cloud, DEM and Orthomosaic) based on the ability to align the photo and the usability of valid tie points within an image. A tie point represents a point that the software determine to be common from one photo to the next. The camera locations CSV file (available in the larger work citation) indicates which photos were used to create the final products. This final point cloud was checked for accuracy only by rotating the point cloud to view from multiple angles to ensure that obvious spurious points do not cause artifacts in the derivative products (DEM and Orthomosaic). Although some outlying points were manually eliminated, there are still many points that likely do not represent ground features, but are instead artifacts generated by moving water surfaces and/or erroneous tie points. Photographs (available in the larger work citation) are the source for the photogrammetric products and are grouped according to region and flight number. Flights 23-27 were acquired on July 12 and are used in the Lake Bluffs project. Flights 28-35 were acquired on July 13. However, flights 27-30 are included in the Charles Point project, and flights 31-35 are in the Sodus North Project. Flights 36-40 were acquired on July 14 and are used in the Greig Street Project.

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 data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.
  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? This data release contains point cloud data in LAZ format (2017042FA_GreigSt_PointCloud.laz) and a browse graphic (2017042FA_GreigSt_PointCloud_browse.jpg). FGDC CSDGM metadata (2017042FA_GreigSt_PointCloud.xml) accompanies the data.
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    This file requires software capable of opening binary LAZ files.

Who wrote the metadata?

Dates:
Last modified: 11-Jun-2018
Metadata author:
U.S. Geological Survey
Attn: Sandra Brosnahan
Physical Scientist
384 Woods Hole Road
Woods Hole, Massachusetts

508-548-8700 x2265 (voice)
508-457-2310 (FAX)
sbrosnahan@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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