Data Management Plan

This data represents a LiDAR (Light Detection & Ranging) gridded bathymetric surface and a gridded relative seafloor reflectivity surface (incorporated into the las format as intensity) for an area of shallow seabed:

1. Surrounding St. Thomas and St. John (STT/STJ): 3m x 3m grid

2. Mouth of Salt River Bay (SARI) in St. Croix: 5m x 5m grid

3. Buck Island Reef National Monument (BUIS) in St. Croix: 3m x 3m grid

Fugro LADS, in collaboration with NOAA's National Ocean Service (NOS), National Centers for Coastal Ocean Science (NCCOS), Center for Coastal Monitoring and Assessment (CCMA), Biogeography Branch, the University of New Hampshire and the National Park Service, acquired bathymetry, relative seafloor reflectivity and hyperspectral imagery in St. Thomas and St. John on thirteen separate dates between 1/29/2011 to 2/28/2011 and in St. Croix (SARI and BUIS) on 2/21/2011 and 2/22/2011.

1. STT/STJ

Bathymetry and reflectivity data were acquired using a LADS (Laser Airborne Depth Sounder) Mark II Airborne System from altitudes between 1,200 and 2,200ft at ground speeds between 140 and 210 knots. The 900 Hertz Nd: YAG (neodymium-doped yttrium aluminum garnet) laser (1064 nm) acquired 3x3 meter spot spacing

and 200% seabed coverage. For STT/STJ, 168.1 square kilometers of LiDAR were collected between 0 m and 40 m in depth. Data was flown for charting. This data met IHO Order 1 standards.

2. SARI

Bathymetry and reflectivity data were acquired using a LADS (Laser Airborne Depth Sounder) Mark II Airborne System from altitudes between 1,200 and 2,200ft at ground speeds between 140 and 175 knots. The 900 Hertz Nd: YAG (neodymium-doped yttrium aluminum garnet) laser (1064 nm) acquired 5x5 meter spot spacing

and 200% seabed coverage. For SARI, 1.62 square kilometers of LiDAR were collected between 0 m and 34 m in depth. This data was collected for research, not charting. It was collected using the same acquistion parameters as STT/STJ, but its uncertainties were not quantified. As such, it is not known if this data meets IHO Order 1 standards.

3. BUIS

Bathymetry and reflectivity data were acquired using a LADS (Laser Airborne Depth Sounder) Mark II Airborne System from altitudes between 1,200 and 2,200ft at ground speeds between 140 and 175 knots. The 900 Hertz Nd: YAG (neodymium-doped yttrium aluminum garnet) laser (1064 nm) acquired 3x3 meter spot spacing

and 200% seabed coverage. For BUIS, 35.9 square kilometers of LiDAR were collected between 0 m and 49 m in depth. This data was collected for research, not charting. It was collected using the same acquistion parameters as STT/STJ, but its uncertainties were not quantified. As such, it is not known if this data meets IHO Order 1 standards.

The data received from NCCOS were in GEOTIFF format for both the lidar and seafloor reflectivity. The NOAA Office for Coastal Management converted these two data sets to text format and then combined them into one text file based on x and y. The text file was then converted to las format, where the seafloor reflectivity is represented as intensity. The data's horizontal coordinate system was NAD83 UTM 20 North, and depth values were collected in meters referenced to Mean Lower Low Water (MLLW) depths. Upon receipt of the data, the NOAA Office for Coastal Management converted the data to geographic coordinates and ellipsoid heights

for data storage and Digital Coast provisioning purposes.

Environmental factors such as wind strength and direction, cloud cover, water clarity and depth influenced the area of data acquisition on a daily basis. The data was processed using the LADS Mark II Ground System and data visualization, quality control and final products were created using CARIS HIPS and SIPS and CARIS BASE Editor. All users should individually evaluate the suitability of this data according to their own needs and standards.

Original contact information:

Contact Org:

National Centers for Coastal Ocean Science (NCCOS), Center for Coastal Monitoring and Assessment (CCMA),

Biogeography Branch

Phone: 301-713-3028

Email: ccma@noaa.gov

Process Steps:

• 2011-01-01 00:00:00 - 1. STT/STJ James Guilford and Scott Ramsay from Fugro LADS led this mapping effort. Hyperspectral data were acquired using a Hyspex VNIR-1600 sensor. Bathymetry and reflectivity data were acquired using a LADS (Laser Airborne Depth Sounder) Mark II Airborne System from altitudes between 1,200 and 2,200ft at ground speeds between 140 and 210 knots. The 900 Hertz Nd: YAG (neodymium-doped yttrium aluminum garnet) laser (1064 nm) acquired 3x3 meter spot spacing and 200% seabed coverage. Green laser pulses are scanned beneath the aircraft in a rectilinear pattern. The pulses are reflected from the land, sea surface, within the water column and from the seabed. The height of the aircraft is determined by the infrared laser return, which is supplemented by the inertial height from the Attitude and Heading Reference System and GPS height. Real-time positioning is obtained by an Ashtech GG24 GPS receiver combined with Wide Area DGPS (Differential Global Positioning System) provided by the Fugro Omnistar to provide a differentially corrected position. Ashtech Z12 GPS receivers are also provided as part of the Airborne System and Ground Systems to log KGPS (Kinetic Global Positioning System) data on the aircraft and at a locally established GPS (Global Positioning System) base station. 2. SARI James Guilford and Scott Ramsay from Fugro LADS lead this mapping effort. Hyperspectral data were acquired using a Hyspex VNIR-1600 sensor. Bathymetry and reflectivity data were acquired using a LADS (Laser Airborne Depth Sounder) Mark II Airborne System from altitudes between 1,200 and 2,200ft at ground speeds between 140 and 175 knots. The 900 Hertz Nd: YAG (neodymium-doped yttrium aluminum garnet) laser (1064 nm) acquired 5x5 meter spot spacing and 200% seabed coverage. Green laser pulses are scanned beneath the aircraft in a rectilinear pattern. The pulses are reflected from the land, sea surface, within the water column and from the seabed. The height of the aircraft is determined by the infrared laser return, which is supplemented by the inertial height from the Attitude and Heading Reference System and GPS height. Real-time positioning is obtained by an Ashtech GG24 GPS receiver combined with Wide Area DGPS (Differential Global Positioning System) provided by the Fugro Omnistar to provide a differentially corrected position. Ashtech Z12 GPS receivers are also provided as part of the Airborne System and Ground Systems to log KGPS (Kinetic Global Positioning System) data on the aircraft and at a locally established GPS (Global Positioning System) base station. 3. BUIS James Guilford and Scott Ramsay from Fugro LADS lead this mapping effort. Hyperspectral data were acquired using a Hyspex VNIR-1600 sensor. Bathymetry and reflectivity data were acquired using a LADS (Laser Airborne Depth Sounder) Mark II Airborne System from altitudes between 1,200 and 2,200ft at ground speeds between 140 and 175 knots. The 900 Hertz Nd: YAG (neodymium-doped yttrium aluminum garnet) laser (1064 nm) acquired 3x3 meter spot spacing and 200% seabed coverage. Green laser pulses are scanned beneath the aircraft in a rectilinear pattern. The pulses are reflected from the land, sea surface, within the water column and from the seabed. The height of the aircraft is determined by the infrared laser return, which is supplemented by the inertial height from the Attitude and Heading Reference System and GPS height. Real-time positioning is obtained by an Ashtech GG24 GPS receiver combined with Wide Area DGPS (Differential Global Positioning System) provided by the Fugro Omnistar to provide a differentially corrected position. Ashtech Z12 GPS receivers are also provided as part of the Airborne System and Ground Systems to log KGPS (Kinetic Global Positioning System) data on the aircraft and at a locally established GPS (Global Positioning System) base station.
• 2011-01-01 00:00:00 - The reflectivity of an LADS pulse is a measure of the amount of energy reflected from the seabed for each individual laser pulse at the wavelength of the laser, 532nm (green/blue). The basic difference between processing an ALB waveform for depth and for reflectivity is that depth processing focuses on the leading edge of the return waveform, whereas reflectivity requires integration of the entire return pulse. Each sounding is assessed for suitability. Dry soundings and soundings in very shallow water are not processed for reflectivity. Each sounding is normalized for the electronic gain applied to the photo multiplier tube to which the received laser energy is optically routed. The gain-normalized return waveform is then analyzed to determine energy returning from the seabed. Integration of the waveform from the seabed will produce a numerical value of reflectivity. To ensure that this value accurately and meaningfully describes variation in seabed reflectivity several parameters must be taken into consideration. Energy is lost from the pulses transmitted from the aircraft. These losses include the air/water interface and those through the water column, and any system specific losses such as optical filtering and receiver field of view. Reflectivity value, calculated for each pulse, is the ratio between the received energy normalized for the losses described and the transmitted energy. Once a relative reflectivity value has been calculated, further statistical cleaning to remove outliers is completed. Because the dataset is of relative reflectivity rather than an absolute value for each point, the entire dataset is scaled to ensure the full dynamic range is used over the dataset. This scaling is applied over an entire survey area to ensure dataset consistency (Collins et al. 2007). Collins et al. 2007 is available online here: http://www.fugrolads.com/datasheets/Hydro_Intl_LiDAR_Seabed_Classification.pdf
• 2013-04-01 00:00:00 - The NOAA Office for Coastal Management received the bathymetric and reflectivity gridded data in GEOTIFF format. The data were in UTM Zone 20N, NAD83 coordinates and were vertically referenced to MLLW. The vertical units of the data were meters. OCM performed the following processing for data storage and Digital Coast provisioning purposes: 1. The bathymetric and reflectivity data were converted from GEOTIFF format to text format. 2. A perl script, brundle.pl was created to combine the bathymetric and reflectivity text data sets into one text file based on x and y. The new text file format was x, y, z, r. 3. The new xyzr text file was processed through VDatum to convert from UTM coordinates to geographic coordinates and to convert from MLLW depths to ellipsoid heights using Geoid12A. 4. Data were converted from txt to las format and the points given a NOAA OCM bathymetric classification of 11 using the lastools tool, txt2las. The reflectivity data were incorporated into the las format and are represented as intensity. 5. Data were filtered for outliers using the lastools tool, las2las 6. Data were zipped to laz format

This data can be obtained on-line at the following URL:

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=1394

This data set is dynamically generated based on user-specified parameters.

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