USGS CoastCam at DUNEX: Intrinsic and Extrinsic Calibration Data (Camera 1)

The CoastCam (camera 1) was used to take IO photos. This involved laying a printed checkerboard with 2.7-centimeter (cm) squares flat and keeping it stationary, then moving the camera to take images of the checkerboard in various parts of the camera’s field of view. An example image can be found in dunex_c1_calibrationIOEO_exampleImagery.zip. There are a total of 19 IO images (dunex_c1_20210914_IO.zip) used for the intrinsic calibration (Bouguet, 2022). These were used in step A in the Camera Calibration procedures outlined in Bruder and Brodie (2020). The resultant parameters are stored in a YML file located in dunex_c1_20210914_IO.zip. Image file naming format follows “dunex_c1_20210914_IO_##”, where dunex is the site name, c1 is the camera name, 20210914 is the date the images were taken (YYYYMMDD format), IO is Intrinsic Orientation, and ## is the image number out of 19 used in the IO calibration process.

EO calibration GCPs were computed from published survey data (Over and others, 2022). GCPs were collected on 20210918. To place the photos taken by the CoastCam into real world coordinates and to rectify them into a planar view, objects within the field of view of the camera must be located. To do so, the elevation and position of the camera lenses in the CoastCam setup were measured with the RTK GPS. Then, multiple stationary targets were spread through the camera field of view to be used as GCPs, and the location of each was measured with the RTK GPS equipment. The GCPs consisted of large square targets, divided into quadrants and colored white and black, and were either made of fabric and laid flat on the ground (center point on ground was surveyed) or made of wood and propped up to face the CoastCam (bottom-center, between black and white at ground level, was surveyed). When all GCPs were in place, a snapshot was taken with the camera (dunex_c1_20210918_GCP_image_raw.jpg). The survey locations of the GCPs in the CSV file were used to hand label the raw image to generate an annotated image (dunex_c1_20210918_GCP_image_annotated.jpg) so that the targets could be labeled correctly in Step B of the Camera Calibration steps in Bruder and Brodie (2020). The pixel coordinates of each GCP within the raw image (hand-selected), solved in Step B of Bruder and Brodie (2020), the GPS positions from the CSV file, and the IO parameters in the IO YML file were used in Step C of the Camera Calibration steps in Bruder and Brodie (2020) to solve for the EO parameters. The resultant parameters for the EO calibration are stored in a YML file located in “dunex_c1_20210918_EO.zip”.

All intrinsic calibration images were given additional information required by the USGS to the exchangeable image file format (EXIF) and other imagery headers using PyExifTool Python library (https://pypi.org/project/PyExifTool/, version: 0.5.6). The following describes the Python dictionary object used, with each entry in the dictionary being a tag-value pair: tags = { 'Copyright': 'Public Domain', 'CopyrightNotice': 'Public Domain - please credit U.S. Geological Survey', 'Artist': 'USGS SPCMSC', 'Make': 'FLIR', 'Model': 'FLIR BFS-PGE-122S6C-C','UserComment': UserComment, 'GPSLatitude': '35.677189', 'GPSLongitude': '-75.480280', 'GPSMapDatum': 'EPSG:6347 (NAD83_National_Spatial_Reference_System_2011)', 'GPSLatitudeRef': 'N', 'GPSLongitudeRef': 'W', 'Credit': 'U.S. Geological Survey', 'Contact': 'gs-g-spcmsc_data_inquiries@usgs.gov', '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", 'AttributionURL': 'https://doi.org/10.5066/P1GDP4HR', 'Contributor': 'Jenna A. Brown, Margaret L. Palmsten, Eric Swanson', 'XMP-photoshop:Credit': 'U.S. Geological Survey', 'iptcCore:CreatorWorkEmail': 'gs-g-spcmsc_data_inquiries@usgs.gov','Rights': 'Public Domain', ‘ExternalMetadataLink:’, "https://www1.usgs.gov/pir/api/identifiers/USGS:874c9b09-e69e-4d71-a4f3-165573139d24", 'Keywords' : "Pea Island National Wildlife Refuge, Outer Banks, North Carolina", 'ImageDescription': 'This image was captured from a stationary mounted camera at Pea Island National Wildlife Refuge, North Carolina. Field Activity Number: 2021-340-FA (https://cmgds.marine.usgs.gov/fan_info.php?fan=2021-340-FA).’, 'Description': ‘This image was captured from a stationary mounted camera at Pea Island National Wildlife Refuge, North Carolina. Field Activity Number: 2021-340-FA (https://cmgds.marine.usgs.gov/fan_info.php?fan=2021-340-FA).’}. The UserComment EXIF metadata field was used to store the camera intrinsics and extrinsics in the image metadata. The UserComment has a nested dictionary structure. The highest-level dictionary contains two nested dictionaries as well as a note explaining the structure of the UserComment field. One nested dictionary contains the actual intrinsic and extrinsic data variables. The other nested dictionary contains text descriptions for each of the variables in the dictionary of data variables. To read out the imagery header information to a CSV file the command is: 'exiftool -csv *.jpg > allheaders.csv'. Specific tags may be specified with this command, if preferred.

All extrinsic calibration ground control point images were given additional information required by the USGS to the exchangeable image file format (EXIF) and other imagery headers using PyExifTool Python library (https://pypi.org/project/PyExifTool/, version: 0.5.6). All extrinsic photos were given EXIF header information in the directory with all the photos by assigning all the tags in a Python dictionary object to each photo using PyExifTool. The following describes the Python dictionary object with each entry in the dictionary being a tag-value pair: tags = { 'Copyright': 'Public Domain', 'CopyrightNotice': 'Public Domain - please credit U.S. Geological Survey', 'Artist': 'USGS SPCMSC', 'Make': 'FLIR', 'Model': 'FLIR BFS-PGE-122S6C-C','UserComment': UserComment, 'GPSLatitude': '35.677189', 'GPSLongitude': '-75.480280', 'GPSMapDatum': 'EPSG:6347 (NAD83_National_Spatial_Reference_System_2011)', 'GPSLatitudeRef': 'N', 'GPSLongitudeRef': 'W', 'Credit': 'U.S. Geological Survey', 'Contact': 'gs-g-spcmsc_data_inquiries@usgs.gov', '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", 'AttributionURL': 'https://doi.org/10.5066/P1GDP4HR', 'Contributor': 'Jenna A. Brown, Margaret L. Palmsten, Eric Swanson', 'XMP-photoshop:Credit': 'U.S. Geological Survey', 'iptcCore:CreatorWorkEmail': 'gs-g-spcmsc_data_inquiries@usgs.gov','Rights': 'Public Domain', ‘ExternalMetadataLink:’, "https://www1.usgs.gov/pir/api/identifiers/USGS:874c9b09-e69e-4d71-a4f3-165573139d24", 'Keywords' : "Pea Island National Wildlife Refuge, Outer Banks, North Carolina", 'ImageDescription': 'This image was captured from a stationary mounted camera at Pea Island National Wildlife Refuge, North Carolina. Field Activity Number: 2021-340-FA (https://cmgds.marine.usgs.gov/fan_info.php?fan=2021-340-FA).’, 'Description': ‘This image was captured from a stationary mounted camera at Pea Island National Wildlife Refuge, North Carolina. Field Activity Number: 2021-340-FA (https://cmgds.marine.usgs.gov/fan_info.php?fan=2021-340-FA).’}. The UserComment EXIF metadata field was used to store the camera intrinsics and extrinsics in the image metadata. The UserComment has a nested dictionary structure. The highest-level dictionary contains two nested dictionaries as well as a note explaining the structure of the UserComment field. One nested dictionary contains the actual intrinsic and extrinsic data variables. The other nested dictionary contains text descriptions for each of the variables in the dictionary of data variables. To read out the imagery header information to a CSV file the command is: 'exiftool -csv *.jpg > allheaders.csv'. Specific tags may be specified with this command, if preferred.