{
    "tag": 12988,
    "title": "EAARL Topography-Dry Tortugas National Park",
    "pubdate": "2006",
    "sername": null,
    "series_name": null,
    "issue": "1244",
    "publish": null,
    "publisher_name": null,
    "onlink": "https:\/\/cmgds.marine.usgs.gov\/catalog\/spcmsc\/of2006-1244metadata.faq.html",
    "format": null,
    "email": null,
    "descript": "Lidar is a remote sensing technique that uses laser light to detect, range, or identify remote objects based on light reflected by the object or emitted through it subsequent fluorescence.  Airborne ranging lidar is now being applied in coastal environments to produce accurate, cost-efficient elevation datasets with high data density.  The USGS in cooperation with NASA and NPS is using airborne lidar to measure the submerged topography of the Dry Tortugas reef tract and Subaerail topography of land features; secondarily, the data will be assessed for its potential in terms of benthic characterization. Elevation measurements were collected over Dry Tortugas National Park using the NASA Experimental Advanced Airborne Research Lidar (EAARL), a pulsed laser ranging system mounted onboard an aircraft to measure subaerial and submarine coastal topography. With the NASA EAARL lidar system, submarine data is generally acquired to a maximum of approximately 1.5 secchi depths (a measure of water clarity).  The system uses a high frequency laser beam directed at the earth's surface through an opening in the bottom of the aircraft's fuselage. The laser system records the time difference between emission of the laser beam and the reception of the reflected laser signal in the aircraft.  The Experimental Advanced Airborne Research Lidar, developed by the National Aeronautics and Space Administration (NASA) Wallops Flight Facility (WFF) in Virginia, measures ground elevation with a vertical resolution of roughly 15 centimeters. A sampling rate of up to 3 kHz results in an extremely dense spatial elevation data set.  For more information on Lidar science and the Experimental Advanced Airborne Research Lidar (EAARL) system and surveys, see http:\/\/ngom.usgs.gov\/dsp\/overview\/index.php and http:\/\/ngom.usgs.gov\/dsp\/tech\/eaarl\/index.php .",
    "lang": null,
    "journal": null,
    "pwid": null,
    "originator": [
        {
            "name": "U.S. Geological Survey",
            "role": "Author"
        }
    ],
    "index_term": [
        {
            "thcode": 2,
            "code": "2041",
            "name": "digital elevation models",
            "scope": "Gridded elevation, geographically referenced to the surface of the earth, as digital data"
        },
        {
            "thcode": 2,
            "code": "648",
            "name": "lidar",
            "scope": "Light detection and ranging, an airborne, spaceborne or ground-based laser-ranging technique commonly used for acquiring high-resolution topographic data."
        },
        {
            "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": 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": 23,
            "code": "3",
            "name": "Distributions",
            "scope": "Locations or patterns of a feature of interest across space and (or) time. These data can include point data, lines, polygons, and temporal data at any scale relevant to CMSP and can be produced by observation, interpolation, or modeling. Distributions can also include maps or statistics of climatology, the environmental values that are expected to be observed at the present time."
        },
        {
            "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": "429",
            "name": "topographic mapping",
            "scope": "used for traditional cartographic methods that document the distribution and elevation of geographic and hydrographic features (and usually cultural features and administrative boundaries)."
        }
    ],
    "place_term": [],
    "image": [],
    "fan": [
        "04LTS05"
    ]
}