Guam and CNMI Underwater Photomosaics

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Time of data collection.

Custom web map app allowing viewing and query of data offshore Guam and Saipan.

This map viewer includes shallow-water (0-50 meter) benthic habitat data collected around Guam and Saipan, Commonwealth of the Northern Mariana Islands (CNMI).

Costa, B., and Sweeney, E. (2024). Characterizing submerged lands around Naval Base Guam, Mariana Islands. NOAA Technical Memorandum NOS NCCOS 329. https://doi.org/10.25923/zwwa-h562

Costa, B., Sweeney, E., and Kraus, J. (2024). Characterizing benthic habitats of western Saipan, CNMI. NOAA Technical Memorandum NOS NCCOS 328. https://doi.org/10.25923/psjm-h924

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This data package contains information and maps showing the geology and biology of select submerged lands (0 to 50 meters deep) around Navy Base Guam (NBG) and Haputo Ecological Reserve Area (ERA) Guam, Mariana Islands. This information and maps were developed using benthic information from underwater photographs, environmental predictor variables derived from satellite imagery and bathymetry, and machine learning modeling approaches.

Costa, Bryan; Sweeney, Edward; Kraus, Jennifer (2024). NCCOS Mapping: Characterizing Benthic Habitats West of Saipan, Commonwealth of the Northern Mariana Islands (CNMI), 2018-11-05 to 2022-04-29 (NCEI Accession 0291792). [indicate subset used]. NOAA National Centers for Environmental Information. Dataset. https://doi.org/10.25921/m0f6-3b26.

This data package contains information and maps showing the geology and biology of select submerged lands (0 to 40 meters deep) offshore of western Saipan, Commonwealth of the Northern Mariana Islands (CNMI). This information and maps were developed using benthic information from underwater photographs, environmental predictor variables derived from satellite imagery and bathymetry, and machine learning modeling approaches.

nccos.data@noaa.gov

The photographs and positioning information were acquired at approximately 668 sites from August 20, 2021 to May 12, 2022. A minimum of 4 square meters of the seafloor was photographed at each site. The process for collecting these overlapping, underwater photographs was identical at each site. A handheld Garmin GPS 76 unit was used to navigate to each site via a small boat. A drop camera system was then lowered to within 1.5 to 2 meters of the seafloor. This drop camera system included: (1) a downward-looking digital single-lens reflex (DSLR) camera (i.e., a Nikon D7500 camera in 2021 and a Sony alpha7 IV mirrorless camera in 2022), (2) two green lasers spaced 10 cm apart, and (3) a Blueprint Subsea SeaTrac ultra-short baseline (USBL) X150 beacon and X010 transponder. In 2022, an oblique-looking GoPro HERO10 Black in a Spot X Squid housing was also included, which provided real-time video topside for situational awareness.

The downward-looking DSLR cameras collected still photographs of the seafloor every 0.5 to 1 s. The camera settings included: focal lengths = 18 mm, white balance = auto, and shutter speed = 1/200 s. Both jpeg and .RAW files were recorded. The photographs overlapped by 60 to 80%. The lasers provided a measurement scale (10 cm) and were visible in some but not all of the photographs. The USBL transponder provided the location and depth (XYZ) of the drop camera every 5 s, and a Trimble GeoXH GPS provided the location of the vessel every 1 s. The Trimble GPS antenna was positioned directly over the USBL transmitter pole to minimize lever arm offsets.

For more information, see:

Costa, B., and Sweeney, E. (2024). Characterizing submerged lands around Naval Base Guam, Mariana Islands. NOAA Technical Memorandum NOS NCCOS 329. https://doi.org/10.25923/zwwa-h562

Costa, B., Sweeney, E., and Kraus, J. (2024). Characterizing benthic habitats of western Saipan, CNMI. NOAA Technical Memorandum NOS NCCOS 328. https://doi.org/10.25923/psjm-h924

Underwater photographs were visually reviewed for quality and color corrected (performed using Adobe Lightroom software). The GPS data were differentially corrected using a Continuously Operating Reference Station on Guam and reprojected to the WGS 1984 UTM 55 North coordinate system (performed using GPS Pathfinder Office software). The USBL data were exported from SeaTrac PinPoint software and matched with the corrected GPS locations using timestamps.

Underwater photographs were georeferenced using these GPSUSBL locations (ESRI, 2023; performed using ArcGIS Pro, Geotagged Photos To Points function). Not all images were georeferenced because sampling frequencies differed among the USBL (approximately 5 s), GPS (approximately 1 s), and cameras (approximately 0.5 to 1 sec). To georeference the remaining photographs, a custom Python script was created to interpolate positions between the GPS-USBL locations. This script also mosaicked and developed 3D models from the resulting georeferenced photographs (Pierce and Winians, 2023; performed using Agisoft Metashape application programming interface).

For more information, see:

Costa, B., and Sweeney, E. (2024). Characterizing submerged lands around Naval Base Guam, Mariana Islands. NOAA Technical Memorandum NOS NCCOS 329. https://doi.org/10.25923/zwwa-h562

Costa, B., Sweeney, E., and Kraus, J. (2024). Characterizing benthic habitats of western Saipan, CNMI. NOAA Technical Memorandum NOS NCCOS 328. https://doi.org/10.25923/psjm-h924

Five to seven substrate and 12 to 14 biological cover types were identified visually in the above georeferenced photographs. The amount of annotated area (four meters squared) was standardized in each photograph so that it matched the spatial resolution (i.e., two x two meter pixels) of the environmental predictors. Multiple substrate and cover types were often present at each site. Percent cover was estimated to the nearest 1% for each habitat type. Percent covers were also converted to presences (1) and absences (0) and used to train or validate the habitat predictions. In Saipan, n =1,109 annotations, where 617 annotations were used for model training and 492 annotations were used for model validation. In Guam, n = 674 annotations, where 346 annotations were used for model training and 328 annotations were used for model validation.

For more information, see:

Costa, B., and Sweeney, E. (2024). Characterizing submerged lands around Naval Base Guam, Mariana Islands. NOAA Technical Memorandum NOS NCCOS 329. https://doi.org/10.25923/zwwa-h562

Costa, B., Sweeney, E., and Kraus, J. (2024). Characterizing benthic habitats of western Saipan, CNMI. NOAA Technical Memorandum NOS NCCOS 328. https://doi.org/10.25923/psjm-h924