Precision Airborne Camera (PAC) System - Field data from periodic and event-response surveys of the U.S. Atlantic and Gulf Coasts

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Frequently anticipated questions:


What does this data set describe?

Title:
Precision Airborne Camera (PAC) System - Field data from periodic and event-response surveys of the U.S. Atlantic and Gulf Coasts
Abstract:
The U.S. Geological Survey (USGS) Remote Sensing Coastal Change (RSCC) project collects aerial imagery along coastal swaths with optimized endlap/sidelap and precise position information to create high-resolution orthomosaics, three-dimensional (3D) point clouds, and digital elevation/surface models (DEMs/DSMs) using Structure-from-Motion (SfM) photogrammetry methods. These products are valuable for measuring topographic and landscape change, and for understanding coastal vulnerability and response to disturbance events. This is an ongoing collection of nadir (vertical) aerial imagery surveys of coastal environments. Low-altitude digital aerial imagery is acquired with a manned, fixed-wing aircraft using the "Precision Airborne Camera (PAC)" system. The system is operated by C.W. Wright and consists of a mounted digital camera fitted with a prime lens, along with a custom integrated survey-grade Global Navigation Satellite System (GNSS) receiver.
Supplemental_Information:
The USGS RSCC Simple Data Distribution Service is designed to release data using a standardized workflow in support of timely best science while maintaining USGS Fundamental Science Practices (FSP) and meeting the high-quality data standards of the USGS. The data service includes big data (up to hundreds of thousands of digital images) and related derivative data products, and serves as a digital data repository for manual, semi-automated, and fully automated retrieval of published data. The data service is structured in a folder (directory) hierarchy with subfolders corresponding to individual data collection platforms (DCPs) or groups of DCPs, which in turn contain folders with products grouped by collection effort. For more information on the RSCC Simple Data Distribution Service, refer to Ritchie and others (2023), https://doi.org/10.5066/P9M3NYWI.
  1. How might this data set be cited?
    Kranenburg, Christine J., Brown, Jenna A., Ritchie, Andrew C., Over, Jin-Si R., Sherwood, Christopher R., and Warrick, Jonathan A., 20231006, Precision Airborne Camera (PAC) System - Field data from periodic and event-response surveys of the U.S. Atlantic and Gulf Coasts: data service DOI:10.5066/P9M3NYWI, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

    Other_Citation_Details:
    Suggested Citation: Kranenburg, C.J., Brown, J.A., Ritchie, A.C., Over, J.R., Sherwood, C.R., and Warrick, J.A., 2023, Precision Airborne Camera (PAC) System - Field data from periodic and event-response surveys of the U.S. Atlantic and Gulf Coasts, in Remote Sensing Coastal Change Simple Data Distribution Service: U.S. Geological Survey data service, accessed [MMMM d, YYYY], at https://doi.org/10.5066/P9M3NYWI. [Data directly accessible at https://cmgds.marine.usgs.gov/data-services/rscc/PrecisionAirborneCameraSystem/]
    This is part of the following larger work.

    Ritchie, Andrew C., Triezenberg, Peter J., Warrick, Jonathan A., Hatcher, Gerald A., and Buscombe, Daniel D., 20230221, Remote Sensing Coastal Change Simple Data Distribution Service: data service DOI:10.5066/P9M3NYWI, U.S. Geological Survey - Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -180
    East_Bounding_Coordinate: 180
    North_Bounding_Coordinate: 90
    South_Bounding_Coordinate: -90
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 30-Nov-2017
    Ending_Date: Present
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: application/service
  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?
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    This metadata record describes characteristics of the Precision Airborne Camera (PAC) system data collection platform (DCP) and the organization and processing steps for data collected from that platform. The images are downloadable as JPEGs (.jpg) and correspond to a single 3-band, 24-bits per pixel, RGB image with imagery header metadata locating the image in space and time and describing acquisition parameters (including but not limited to: camera model, camera settings, lens information, and image conversion parameters). Datasets are organized by directory with each directory (folder) corresponding to a single collection effort. Product types (raw imagery, derivatives, and any ancillary products) for each collection effort are organized in subfolders with associated metadata and are populated as data are processed. In some cases, multiple versions or formats of a product may be released, including emergency and provisional data subject to change. Process steps in the collection-level metadata for each product describe naming conventions, methods, and disclaimers. Directory structure for each survey uses the following naming convention: {State[-State]}_{Region/Coast}_{YYYYMMDD[-YYYYMMDD]}_{Event}, where {State[-State]} is the two-letter abbreviation for the state[-s] (in alphabetical order) where the survey event occurred, {Region/Coast} is a unique name for the specific survey location (for example, "Atlantic" or "Gulf" for Florida coastal surveys), {YYYYMMDD[-YYYYMMDD]} is the abbreviation for the date[-s] the survey occurred, and {Event} describes a response to a specific event (when applicable) such as "preIan" and "postIan" for pre- and post-Hurricane Ian surveys.
    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
    • Andrew C. Ritchie
    • Jin-Si R. Over
    • Christopher R. Sherwood
    • Jonathan A. Warrick
  2. Who also contributed to the data set?
    Data collection was funded by the U.S. Geological Survey. The authors would like to thank pilot Wayne Wright of C.W. Wright Consulting (https://lidar.net) for data acquisition and systems expertise.
  3. To whom should users address questions about the data?
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
    SPCMSC Data Management Group
    600 4th St South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    gs-g-spcmsc_data_inquiries@usgs.gov

Why was the data set created?

These data are provided to record ground conditions at a high temporal and spatial resolution, and after high-magnitude disturbance events, to improve our understanding of earth surface processes (natural hazards) affecting coastal resources.

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: Not complete (process 1 of 7)
    IMAGE & POSITION ACQUISITION -- C. W. Wright Consulting operates the Precision Airborne Camera (PAC) system to conduct nadir (vertical) aerial imagery surveys along coastal swaths in shore-parallel lines with optimized endlap/overlap to facilitate SfM processing (Westoby and others, 2012). The PAC system is comprised of a high-resolution digital camera fitted with a prime lens, along with a custom integrated survey-grade Global Navigation Satellite System (GNSS) receiver aboard a Piper P28A aircraft. The camera is triggered by a microcontroller that is synchronized to the pulse-per-second (PPS) signal from the survey-grade GNSS. An event mark is then captured from the flash shoe, timestamped by the GNSS and recorded by the microcontroller. The dataset received from the vendor is comprised of the raw imagery, raw dual-frequency carrier phase GNSS data and photo flash event time data. GNSS positions record the phase center of the GNSS antenna at the moment an image is captured (see Positional_Accuracy metadata element for uncertainty discussion). Lever arm distances are used to translate the position from the nodal point of the camera lens to the GNSS antenna reference point (for more details see Over and others, 2021); these are recorded relative to the camera coordinate system, where the camera is 0,0, and the axes run as follows: X axis runs from left (negative) to right (positive) Y axis runs from bottom (negative) to top (positive) Z axis runs from front of lens (negative) to back of camera (positive) The PAC system hardware is updated as new technological advances are available, which may include a new camera and/or new GNSS system, which may also change the lever arm distances; estimated uncertainties in the lever arm distances are 5 cm in each direction. Below are the specifications of the different PAC system versions and the dates they were in use: VERSION 1.1 Survey Dates Valid: 20171130 - 20180807 Camera Model: Ricoh GRII GNSS Survey Equipment: GPS-only system Lever Arm Distances: 0.44 m, -0.31 m, and 1.25 m (x, y, z) VERSION 1.2 Survey Dates Valid: 20180808 - 20180907 Camera Model: Sony A7R 36 Megapixel GNSS Survey Equipment: GPS-only system Lever Arm Distances: 0.44 m, -0.31 m, and 1.25 m (x, y, z) VERSION 2 Survey Dates Valid: 20180908 - Present Camera Model: Sony A7R 36 Megapixel GNSS Survey Equipment: GPS & GLONASS system Lever Arm Distances: 0.1 m, -0.15 m, and 1.25 m (x, y, z) Data sources produced in this process:
    • raw imagery
    • raw GNSS
    • event marks
    Date: Not complete (process 2 of 7)
    IMAGE RENAMING -- Images received from the vendor (in raw image file format, ARW) are renamed using IrfanView software to conform to the following naming convention: yyyy-mmdd-hhmmss-DSCnnnnn-N7251F.ARW, where yyyy_mmdd represents the year (yyyy), month (mm) and day (dd) of capture; hhmmss is the time of capture as hours (hh), minutes (mm), seconds(ss) in Universal Coordinated Time (UTC); DSCnnnnn represents a sequential image identifier (ID) generated by the camera; and N7251F is the tail number of the aircraft used for acquisition. The following pattern string is used in the batch renaming tool to rename the images from their raw name format (DSCnnnnn) to the naming convention defined above: $E36868(%Y-%m%d-%H%M%S)-$N-N7251F Data sources used in this process:
    • raw imagery
    Data sources produced in this process:
    • renamed imagery
    Date: Not complete (process 3 of 7)
    IMAGE CONVERSION -- Renamed images are batch-converted to a format compatible with photogrammetry processing software using Adobe Photoshop Camera Raw and applying the Camera Neutral Profile (Joint Photographic Experts Group format, JPEG) and saving at quality 12 (max) using sRGB color space at 8 bits/channel. Software versions, conversion date, and other parameters are recorded in individual imagery header metadata. Data sources used in this process:
    • renamed imagery
    Data sources produced in this process:
    • jpg imagery
    Date: Not complete (process 4 of 7)
    IMAGE QA/QC -- Original and converted images are counted, and the beginning and end of the survey are reviewed to cull extraneous images (such as camera testing or inadvertently triggered images). A multi-page contact sheet of images is created to allow quick review ensuring that (a) conversion was successful with no corrupted imagery, and (b) "extra" imagery not capturing the intended view is culled. If corrupted converted images are found, imagery is re-converted until a collection of valid images remains. Note that in some cases, water-only images may be retained if there are visible or potentially visible bathymetric features, aquatic vegetation, and/or objects in the scene that may be useful for future data applications. Data sources used in this process:
    • populated imagery
    Data sources produced in this process:
    • publication-ready imagery
    Date: Not complete (process 5 of 7)
    AIRCRAFT NAVIGATION PROCESSING -- Raw GNSS data received by the antenna mounted atop the aircraft were recorded at 1 hertz (Hz) by a dual-frequency survey-grade GNSS receiver, which is post-processed and differentially corrected with as many continuously operating reference stations (CORS) within 30 kilometers (km) of any part of the trajectory, or locally-established base station(s) if necessary, using NovAtel's GrafNav software to produce 1-Hz aircraft trajectories. Trajectories are produced using precise ephemerides unless the flight level metadata clearly describes the dataset as PROVISIONAL, in which case a lower accuracy ephemeris is used. This is sometimes necessary if the imagery is collected to rapidly assess damage from natural disasters. The aircraft trajectories, in combination with precisely recorded image capture (flash event) times, are used to generate aircraft GNSS antenna positions at the moment of each image capture and is provided for each collection. Images with missing positions are reconciled through direct interpolation based on the image and GNSS time stamps. The positions in the aircraft positions file represent the position of the aircraft GNSS antenna, not the position of the camera or features photographed. To determine actual image positions, photogrammetric software such as Agisoft Metashape can be used to apply the lever arm offsets (in the camera frame of reference) from the GNSS antenna reference point to the camera lens. Data sources used in this process:
    • raw GNSS
    • event marks
    • jpg imagery
    Data sources produced in this process:
    • picture positions
    Date: Not complete (process 6 of 7)
    IMAGERY HEADERS -- Georeferencing, copyright, and other relevant information is added to the imagery headers of each image using Phil Harvey's ExifTool. To extract the information from the image headers using ExifTool, the following command can be used: exiftool -n -csv *.jpg > allheaders.csv The -csv flag writes the information out in a comma-delimited format. The -n option formats the latitude and longitude as signed decimal degrees. Data sources used in this process:
    • jpg imagery
    • picture positions
    Data sources produced in this process:
    • populated imagery
    Date: Not complete (process 7 of 7)
    KMZ CREATION -- In order to provide a visual map of the survey extent with example images throughout the survey domain, and to aid in completing the geospatial information in the collection-level metadata, a clickable Keyhole Markup Language Zipped file (.kmz) is created for each collection using ExifTool. Data sources used in this process:
    • populated imagery
    Data sources produced in this process:
    • kmz
  3. What similar or related data should the user be aware of?
    Westoby, Matthew J., Brasington, James, Glasser, Neil F., Hambrey, Michael J., and Reynolds, John M., 20121215, 'Structure-from-Motion' photogrammetry: A low-cost, effective tool for geoscience applications: Geomorphology vol. 179, Elsevier, Amsterdam, Netherlands.

    Online Links:

    Other_Citation_Details: pages 300-314
    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: U.S. Geological Survey Open-File Report 2021-1039, U.S. Geological Survey, Reston, VA.

    Online Links:


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

  1. How well have the observations been checked?
    The accuracy of the position data is based on the accuracy and precision of the GNSS equipment, camera timing, number and length of baselines, and atmospheric conditions, and is listed in the collection-level metadata. Note that the positions in the imagery headers are aircraft GNSS antenna positions and are limited to six decimal places. Whereas the positions in the external navigation file are accurate to ten decimal places and are therefore highly recommended for use in SfM photogrammetric processing to produce the highest quality derived products. No effort is made to optimize exposure through post-processing. These data represent raw aerial imagery, as collected, and subsequently used in SfM photogrammetric processing workflows.
  2. How accurate are the geographic locations?
    Horizontal positions are provided in the aircraft positions files (.txt) and generally have an estimated 2-sigma horizontal accuracy of 10 centimeters (cm). The accuracy of the positions in the imagery headers are reduced due to field size limitations for storing latitude/longitude. Any variations in positional accuracy are described in the collection-level metadata record.
  3. How accurate are the heights or depths?
    Vertical positions are provided in the aircraft positions files (.txt) and generally have an estimated 2-sigma vertical accuracy of 15 cm. Any variations in positional accuracy are described in the collection-level metadata record.
  4. Where are the gaps in the data? What is missing?
    This is an ongoing collection of nadir (vertical) aerial imagery surveys of coastal environments. Some images may lack position information in their imagery header metadata resulting from a momentary disruption in GNSS signals but in most cases, interpolated positions were applied to these images.
  5. How consistent are the relationships among the observations, including topology?
    RGB (red, green, blue) values are 8-bits per band, generally not saturated or underexposed. In a few cases of high or low light conditions, some imagery may be over or underexposed. GNSS values are checked for consistency and outliers. Bad data are discarded, and missing data are interpolated based on GNSS timestamps.

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)
    SPCMSC Data Management Group
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
    600 4th St. 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? yyyy-mmdd-hhmmss-DSCnnnnn-N7251F.jpg
  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?

Who wrote the metadata?

Dates:
Last modified: 03-Oct-2023
Metadata author:
U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
Attn: SPCMSC Data Management Group
600 4th St. South
St. Petersburg, FL
USA

727-502-8000 (voice)
gs-g-spcmsc_data_inquiries@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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