Elwha PlaneCam - aerial imagery and derivatives from Elwha River (WA) flight on July 25th, 2017

Acquisition -- Aerial imagery was collected using a DOI-contracted aircraft operated by Rite Bros. Aviation. Cameras were mounted in wing inspection plates and triggered with internal software intervalometers to capture imagery. Images were acquired in jpg format. Any position data are added in post-processing and not natively collected, derived through photogrammetry and/or ground-control.

Image renaming -- Raw Images are renamed using Phil Harvey's EXIFTOOL with the following command: exiftool -P -r -f -api missingtagvalue="000" -d %Y%m%d%H%M%S "-filename<${DateTimeOriginal}_SN${SerialNumber;$_=substr($_,-3)}_${PreservedFileName;s/\.\w*$//}.%e" -ext jpg . files follow the following naming convention: {YYYYMMDDHHMMSS}_{SN###}_{PreservedFileName}.jpg, where {YYYYMMDDHHMMSS} is the image acquisition time in {YearMonthDayHourMinuteSecond} expressed in 24-hour time, as recorded by the camera’s internal clock or subsequently adjusted and written to the DateTimeOriginal field in the image EXIF data, {SN###} is the last 3 digits of the camera serial number OR 000 in the case the camera doesn't have a serial number, preceded by the letters “SN”, and {PreservedFileName} is the original filename recorded at the time the image was captured. For example, 20120319123426_SN000_IMG_1082.JPG would be the filename for an image with a DateTimeOriginal EXIF time/date stamp of March 19th, 2012, at 12:34:26 pm in Pacific Standard Time (PST) - See attribute accuracy report in platform metadata for details on time accuracy.

Image QA/QC -- original and renamed images are counted, and the beginning and end of the survey are reviewed to cull extraneous images such as images before takeoff and after landing (see logical consistency section for details). Corruped images are identified using ImageMagick with GNU Parallel. #example command to identify corrupt images: find . -iname "*.jpg"| parallel magick identify -regard-warnings {} >> magick_log.txt 2>>magic_err_log.txt If corrupted images are found, they are replaced from backup sources created when downloading imagery if possible. If corrupted images are not recoverable (for example, original imagery is corrupt) the images are deleted. Note that images of water and sky captured on turns are typically retained in this dataset.

Position data processing -- because source data are not georeferenced, position data are only derived through ground control (GCPs), or 4D SfM when imagery is coaligned with imagery containing GNSS coordinates (Such as the PCMSC PlaneCam). When collected, GNSS data are post-processed to derive the precise position of ground control points, check points, and/or the GNSS antenna at the time of image acquisition. If necessary for rapid processing, approximate (PROVISIONAL) positions are produced from rapid ephemeris data. After precise ephemerides are available, GNSS data are post-processed to calculate GNSS trajectory, and precise positions are derived from station occupations or event marks recorded with precision timing, placed along the GNSS trajectory. Processing workflows, accuracy estimates, software and version are detailed in GNSS metadata. Camera and ground control positions are post-processed together with images, camera lever arm data and photogrammetric software to derive accurate camera position and pose.

Photogrammetric Processing -- 3D or 4D structure-from-motion (SfM) processing, as described in Over and others (2021) and Warrick and others (2017), is used to derive camera positions for surveys missing position data if necessary. This processing is done with reduced accuracy to provide approximate location only.

Imagery EXIF coordinates reconciliation -- Note that EXIF camera positions are not intended to be suitable accuracy for precise photogrammetric surveys, but they are used to populate the EXIF metadata field and locate the image in space relative to other images for reference purposes. GNSS/SfM position data published separately from images should be used for SfM reconstruction if available. CAMERA POSITIONS ARE NOT NECESSARILY PRESENT OR ACCURATE IN EXIF DATA. For this platform, no positions are recorded initially, and if added, the positions may not be the definitive set. Depending on availability of position data, coordinates for image EXIF position data are recorded as follows, with the appropriate indicator written to the EXIF:GPSAreaInformation tag: 1) If no position data are calculated, the EXIF:GPSAreaInformation tag will be blank/absent 2) If image positions have been calculated using 4D_sfm- or GCP-derived photogrammetry, EXIF:GPSAreaInformation="structure-from-motion" 3) If a sequence of images are unaligned from photogrammetry, but can be interpolated (for example, on a turn between lines), EXIF:GPSAreaInformation="interpolated" 4) If a sequence of images are unaligned from photogrammetry at the beginning or end of a flight, they will be extrapolated to the estimated takeoff location, EXIF:GPSAreaInformation="interpolated"

Image EXIF annotation -- Additional information was added to individual image EXIF tags using the command-line 'exiftool' software with the following command, as appropriate: #tags for provisional data exiftool ^ -P ^ -IPTC:Credit="U.S. Geological Survey" ^ -IPTC:Contact="pcmsc_data@usgs.gov" ^ -EXIF:Copyright="Public Domain" ^ -XMP:UsageTerms="These data are preliminary or provisional and are subject to revision. They are being provided to meet the need for timely best science. The data have not received final approval by the U.S. Geological Survey (USGS) and are provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the data." ^ -overwrite_original *.JPG #tags for approved data exiftool ^ -P ^ -IPTC:Credit="U.S. Geological Survey" ^ -IPTC:Contact="pcmsc_data@usgs.gov" ^ -EXIF:Copyright="Public Domain" ^ -XMP: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." ^ -EXIF:ImageDescription="[single_image_EXIF_desc]" ^ -XMP:AttributionURL="https://doi.org/10.5066/P9M3NYWI ^ -EXIF:GPSAreaInformation="[position_method]" ^ -EXIF:GPSMapDatum="EPSG:4326 (WGS 84)" ^ -overwrite_original *.JPG tags were then duplicated to XMP headers to increase tag compatibility for image viewing software with the following exiftool command #tag duplication per phil harvey exiftool ^ -P ^ "-XMP-photoshop:Credit<IPTC:Credit" ^ "-XMP-iptcCore:CreatorWorkEmail<IPTC:Contact" ^ "-XMPdc:Rights<EXIF:Copyright" ^ "-XMP-dc:Description<EXIF:ImageDescription" ^ "-XMP-exif:all<GPS:all" ^ "-XMPexif:GPSLatitude<Composite:GPSLatitude" ^ "-XMP-exif:GPSLongitude<Composite:GPSLongitude" ^ "-XMPexif:GPSDateTime<Composite:GPSDateTime" ^ "-XMP-photoshop:DateCreated<EXIF:DateTimeOriginal" ^ "-XMPxmp:ModifyDate<EXIF:ModifyDate" ^ "-XMP-dc:Creator<EXIF:Artist" ^ "-XMP-tiff:Make<EXIF:Make" ^ "-XMPtiff:Model<EXIF:Model" ^ -overwrite_original *.JPG