Backscatter imagery extracted from gridded bathymetry of Ni'ihau Island, Hawaii, USA. These data provide almost complete coverage between 0 and 100 meters. The backscatter dataset includes Simrad EM3002d, Simrad EM300 and Reson 8101 data. The sonars frequencies are 300 kHz,30kHz and 240 kHz respectively and are processed and gridded separately. Because of the similar sonar frequencies the data can be mosaicked nearly seamlessly using GIS software. This metadata is for the Simrad em3002d backscatter data only.
The geotiffs of backscatter imagery were created using data gathered from multibeam soundings for use as a planning and reference document. The data are also being used for benthic habitat mapping, for locating Essential Fish Habitat, and for studying geologic features of the area. Refer to supplemental information for description of instrument and survey.
Data were collected aboard the NOAA Ship Hi'ialakai, a 218' United States National Oceanographic and Atmospheric Agency research ship. The NOAA Ship Hiialakai's survey sensors include a 30 kHz Simrad EM300 sonar and a 300 kHz Simrad EM3002d sonar, which provide bathymetry and backscatter data, a TSS/Applanix POS/MV Model 320, which measures position, velocity, attitude and heading, and a Seabird SBE 9/11 plus CTD used to measure sound velocity profiles. Specific equipment configurations are documented in cruise metadata from cruises HI0504.
ground condition
These data are not to be used for navigation purposes. Please acknowledge NOAA (Office of Ocean Exploration and the Pacific Islands Fisheries Science Center) and the Joint Institute for Marine and Atmospheric Research (JIMAR) University of Hawaii as the sources of this information.
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http://www.soest.hawaii.edu/pibhmc/MHI_images/NII_bs_em3002_440.jpg
Benthic Habitat Mapping Group, Coral Reef Ecosystem Division (CRED), Pacific Islands Fisheries Science Center (PIFSC), NOAA and the Joint Institute for Marine and Atmospheric Research (JIMAR) are the sources of this information.
Data are collected for resource management and research purposes and are tested for internal consistency; however, no effort is made to compare these data to external references or to other published data.
These data are believed to be logically consistent though no tests were performed
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Horizontal positioning system: GPS (SPS) Horizontal position accuracy: 25 meters
1m Range resolution of sonar ~1.25 cm Raw sounding resolution: Variable Vertical accuracy of gridded product: 1% of water depth
Science Applications International Corporation's (SAIC) ISS-2000 acquires, processes and records data, provides survey control and underway quality control displays. SAIC's SABER processing software is used to process the raw soundings, analyze the results, manually edit the sounding data to remove outliers and derive average gridded data values. Additional data acquisition and processing information can be found in the metadata for cruises HI0504. Hawaii Mapping Research Group (HMRG) processing software was then used to extract values of acoustic intensity from the soundings. HMRG is an organization of scientists, engineers and technicians whose mission is to design, build, and operate tools for mapping the seafloor. HMRG is a group within the School of Ocean and Earth Science and Technology at the University of Hawaii at Manoa. The gsf2bs program (July, 2005) converts the swath bathymetry ping records contained within a GSF (Generic Sensor Format) version 2.02 dataset into bs file format. This is done as follows: (i) position each beam's bottom detect intensity sample at the across-track location of that beam's bathymetry value; (ii) assuming a flat bottom in the near neighborhood of the beam, compute across-track distances for all of the beam's remaining intensity samples based on their temporal relation to the bottom detect sample and the computed average sound velocity for that beam as derived from its range and travel time; (iii) after all of the intensity samples from all beams of a ping have been located in across-track distance, fill the gaps between them as necessary by interpolation. The conversion described above is necessary in order to run HMRG backscatter processing operations on the data, such as filtering to remove noise, and to create netCDF grids, raster images and GeoTIFF's. For more information on the backscatter processing technique see <http://www.soest.hawaii.edu/pibhmc>. The backscatter mosaic served here was created using the Mosaic to New Raster in the ArcMap Version 9.3 Toolbox and exported from ArcGIS as a GeoTIFF file to create images containing the em3002d backscatter data from the 2005 and 2006 surveys. Software_Used: SAIC ISS-2000 Acquisition Software, v 3.4 (20030610) SAIC SABER Processing Software, v 2.0.2 (20030610) Hawaii Mapping Research Group (HMRG) Processing Software GMT Generic Mapping Tools, v 4.4 (20090216) MB System, v 5.1.2beta05 ESRI ArcMap 9.x
Backscatter data within a GSF file are arranged as small sequences of intensity values, one sequence per beam per ping. The intensity values represent the amplitude of echo returns to the sensor and can be related to seabed hardness and roughness.
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These data are not to be used for navigational purposes. NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA cannot assume liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.
TIFF is a format for storage, transfer, display, and printing of raster images. The TIFF file structure allows both the ta and the image data to be encoded into the same file. GeoTIFF refers to a TIFF file that has geographic data embedded as tags within the TIFF file. The geographic data can be used to position the image in the correct location and geometry on the screen of a geographic information display. Any GIS, CAD, Image Processing, Desktop Mapping and other types of systems using geographic images can read any GeoTiff file. More specifically, files of this type can be added to ArcInfo and ArcView 8.x or higher and may be viewed in the Table of Contents as a new raster layer. Image visualization software that does not use geography as a basis for image placement can view a GeoTIFF image as if there were no geographic information in the TIFF file. For example, GeoTIFF files can be viewed using Windows Picture and Fax viewer.The GeoTIFF format is public domain, non-proprietary.
