{
    "tag": 14445,
    "title": "Refraction-corrected bathymetric point cloud from the UAS survey of the coral reef off Waiakane, Molokai, Hawaii, 24 June 2018",
    "pubdate": "20220321",
    "sername": null,
    "series_name": null,
    "issue": "DOI:10.5066\/P9XZT1FK",
    "publish": null,
    "publisher_name": null,
    "onlink": "https:\/\/cmgds.marine.usgs.gov\/catalog\/pcmsc\/DataReleases\/ScienceBase\/DR_P9XZT1FK\/Waiakane_2018-06-24_refraction_corrected_point_cloud_metadata.faq.html",
    "format": null,
    "email": null,
    "descript": "This portion of the data release presents a bathymetric point cloud from an unoccupied aerial system (UAS) survey of the coral reef off Waiakane, Molokai, Hawaii, on 24 June 2018. The point cloud has been corrected for the effects of refraction using the techniques described in Dietrich (2017a). The point cloud was created from structure-from-motion (SfM) processing of aerial imagery collected using a UAS with a Ricoh GR II digital camera fitted with a circular polarizing filter. During the survey, a pressure sensor was deployed in the survey area to gain an accurate measurement of the water surface elevation (WSE). After a preliminary dense point cloud was derived from SfM processing, the WSE was used to calculate apparent water depths. These apparent depths along with the estimated camera positions and orientations were used as inputs for the multi-view refraction correction python script (py_sfm_depth.py) described in Dietrich (2017b). The refraction-corrected point cloud showed a substantial improvement in accuracy over the uncorrected point cloud. When compared to the 2013 U.S. Army Corps of Engineers Topobathy Lidar for the area in the central portion of the data set the vertical RMSE for the refraction-corrected point cloud was 0.241 meters with a mean residual of -0.010 meters, whereas the vertical RMSE for the uncorrected point cloud was 0.426 meters with a mean residual of -0.334 meters (see the Vertical Positional Accuracy Report in the metadata for a complete description of the accuracy analysis). For this data release, the final refraction-corrected point cloud is presented in the LAZ format (LAS 1.2 specification). The point cloud has 35,083,205 points with an average point spacing of 0.07 meters. Each point in the point cloud contains an explicit horizontal and vertical coordinate and red, green, and blue (RGB) color values. References Cited: Deitrich, J.R., 2017a, Bathymetric Structure-from-Motion: extracting shallow stream bathymetry from multi-view stereo photogrammetry: Earth Surface Processes and Landforms, https:\/\/doi.org\/10.1002\/esp.4060. Deitrich, J.R., 2017b, py_sfm_depth: Github online repository, https:\/\/github.com\/geojames\/py_sfm_depth.",
    "lang": null,
    "journal": null,
    "pwid": null,
    "originator": [
        {
            "name": "Logan, Joshua B.",
            "role": "Author"
        },
        {
            "name": "Storlazzi, Curt D.",
            "role": "Author"
        }
    ],
    "index_term": [
        {
            "thcode": 2,
            "code": "15",
            "name": "aerial photography",
            "scope": "The process of taking pictures with a camera from an aircraft. Use for both the process of photography from the air and the images produced by the process."
        },
        {
            "thcode": 2,
            "code": "468",
            "name": "geomorphology",
            "scope": "Branch of geology dealing with surface land features and the processes that create and change them."
        },
        {
            "thcode": 2,
            "code": "474",
            "name": "geospatial datasets",
            "scope": "Collections of related digital information that are geographically referenced."
        },
        {
            "thcode": 2,
            "code": "2046",
            "name": "image mosaics",
            "scope": "Composite images formed by overlapping existing images, typically arranged to achieve greater spatial coverage."
        },
        {
            "thcode": 2,
            "code": "981",
            "name": "remote sensing",
            "scope": "Acquiring information about a natural feature or phenomenon, such as the Earth's surface, without actually being in contact with it. USGS remote sensing is usually carried out with airborne or spaceborne sensors or cameras."
        },
        {
            "thcode": 2,
            "code": "2265",
            "name": "structure from motion",
            "scope": "Mathematical analysis, using photogrammetric principles, of multiple images that depict the same subject from different angles to derive geometrical information and relationships in three-dimensional space that are not inherent in any single image. Often used for deriving land elevation or large scale orthoimagery from a collection of aerial photographs."
        },
        {
            "thcode": 2,
            "code": "1749",
            "name": "topographic maps",
            "scope": "Maps depicting the elevation and relief of the land surface or depth of a water body (bathymetry) in an area, usually shown using contour lines.  Typically these maps include manmade features and administrative boundaries as well as vegetation and hydrographic features."
        },
        {
            "thcode": 2,
            "code": "1176",
            "name": "topography",
            "scope": "Configuration of the land surface and sea floor."
        },
        {
            "thcode": 15,
            "code": "006",
            "name": "elevation",
            "scope": "Height above or below sea level, for example altitude, bathymetry, digital elevation models, slope, derived products, DEMs, TINs"
        },
        {
            "thcode": 15,
            "code": "008",
            "name": "geoscientificInformation",
            "scope": "Information pertaining to earth sciences, for example geophysical features and processes, geology, minerals, sciences dealing with the composition, structure and origin of the earth's rocks, risks of earthquakes, volcanic activity, landslides, gravity information, soils, permafrost, hydrogeology, groundwater, erosion"
        },
        {
            "thcode": 23,
            "code": "22",
            "name": "Bathymetry and Elevation",
            "scope": "Includes measures of the height of a location above or below a reference surface. Bathymetry is the elevation of the Earth's surface beneath a body of water, especially the ocean, typically determined by measurements of depth from the water surface at mean lower low water. Distributions are topographic maps and bathymetric charts based on collected data and also include smoothed or gridded maps of bathymetry and elevation from observational data or other associated factors. Assessment data types include models of ecological value, economic value, or current rates of alterations due to erosion, accretion, climate change, and other stressors (for example, wetland habitat loss). Predictions are the results of models or projections of future distributions, values, or ecological impacts of bathymetry, including predicted changes due to natural and human forces such as erosion, deposition, sea-level rise, and dredging activities; predictions also include the results of scenario-based models of bathymetry changes under different management strategies."
        },
        {
            "thcode": 61,
            "code": "450",
            "name": "aerial and satellite photography",
            "scope": "used for vertical or oblique photography of the Earth taken from aircraft or satellites; do not use for air-to-air photography."
        },
        {
            "thcode": 61,
            "code": "447",
            "name": "altimetry",
            "scope": "used for all instruments and techniques that determine altitude, either directly or remotely, including (but not limited to) pressure altimeters, radar altimeters, GPS, and LIDAR."
        },
        {
            "thcode": 61,
            "code": "14",
            "name": "coastal processes",
            "scope": "oceanographic and geologic processes that cause changes to the shoreline and coastal zone."
        },
        {
            "thcode": 61,
            "code": "283",
            "name": "coral reefs",
            "scope": "aquatic biogenic structures supporting a complex community of organisms with distinct roles in relation to the whole: framework builders (corals), along with binders, bafflers, dwellers, and destroyers."
        },
        {
            "thcode": 61,
            "code": "161",
            "name": "fringing reef",
            "scope": "coral reef attached to the shore."
        },
        {
            "thcode": 61,
            "code": "452",
            "name": "orthophotography",
            "scope": "aerial photography corrected for distortion (\"orthorectified\") to create an image with uniform scale."
        },
        {
            "thcode": 61,
            "code": "445",
            "name": "photography",
            "scope": "limited to photography for scientific purposes."
        },
        {
            "thcode": 61,
            "code": "159",
            "name": "reef",
            "scope": "used for 1) shallow-water biotic reefs such as coral reefs, 2) biotic reefs preserved in the geologic record, and 3) rocky outcrops on the sea floor that create a hazard to navigation."
        },
        {
            "thcode": 61,
            "code": "449",
            "name": "remote sensing",
            "scope": "generally used for the acquisition of images or other data from aircraft or satellites; also used for ground-based systems for collecting data at a distance."
        }
    ],
    "place_term": [],
    "image": [
        {
            "name": "https:\/\/www.sciencebase.gov\/catalog\/file\/get\/61b7b89dd34e9e224abffd87?name=Waiakane_2018-06-24_refraction_corrected_point_cloud_browse.jpg&allowOpen=true",
            "description": "Top panel shows a perspective view of the Waiakane point cloud from the 24 June 2018 UAS survey; bottom left plot shows the vertical error distribution for uncorrected (top, purple) and refraction-corrected (bottom, orange) point clouds when compared to the USACE NCMP Topobathy Lidar; bottom right panel shows SfM depths vs Topobathy Lidar depths for the uncorrected (purple) and refraction-corrected (orange) point clouds."
        }
    ],
    "fan": [
        "2018-617-FA"
    ]
}