Gridded bathymetry shelf, bank and slope environments of Ni'ihau Island. This 5 m grid contains data between 0 and 100 meters. The netCDF and Arc ASCII grids include multibeam bathymetry from the Simrad EM300 and Reson 8101 multibeam sonars collected as of December 2009 by the NOAA Coral Reef Ecosystem Division. The sonar frequencies are 30 and 240 kHz respectively.
These netCDF and ASCII grids 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.
Multibeam data were collected aboard the NOAA Ship Hi'ialakai, 218' United States National Oceanographic and Atmospheric Administration research ship. The NOAA Ship Hi'ialakai's survey sensors include a 30 kHz Simrad EM300 sonar and a 300 kHz Simrad EM3002d sonar, which provide bathymetry and imagery 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. Multibeam data were also collected aboard the R/V AHI (Acoustic Habitat Investigator), a 25' survey launch owned and operated by the NOAA Pacific Islands Fisheries Science Center in Honolulu, HI. The R/V AHI's survey sensors include a 240 kHz RESON 8101-ER sonar providing bathymetry and imagery data, a TSS/Applanix POS/MV Model 320 which measures position, velocity, attitude and heading, and a Seabird SBE 19 CTD used to measure sound velocity profiles. Specific equipment configurations are documented in cruise metadata from the following cruises: HI0504. These metadata can be accessed at: http://www.soest.hawaii.edu/pibhmc/cms/cruise-catalog/
ground condition
These data are not to be used for navigation purposes. Please acknowledge NOAA Pacific Islands Fisheries Science Center, and the Joint Institute for Marine and Atmospheric Research (JIMAR) University of Hawaii as the sources of this information.
NOAA IRC
NMFS/PIFSC/CRED
1845 WASP Blvd., Building 176
e-mail preferred
http://www.soest.hawaii.edu/pibhmc/MHI_images/NII_5m_440.jpg
PIBHMC, CRED, PIFSC, NOAA and JIMAR
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
Complete
Horizontal positioning system: GPS (SPS) Horizontal position accuracy: 25 m
1 m Raw sounding resolution: Variable
Multibeam swath files are acquired around the island and in the Generic Sensor Format (GSF) and are edited on a swath by swath basis using SAIC's SABER editing software. The edited swath files are then combined into a Pure File Magic (PFM) format with a defined grid cell size (5 m) in SABER and area based editing is performed. The edited PFM is then exported as X,Y,Z data with a value at each grid node. The X,Y,Z data are then gridded using nearneighbor, a Generic Mapping Tools (GMT) algorithm that converts an ASCII or binary table to a netCDF grid file format. NetCDF grids are then converted to an ArcGIS ASCII file format using LINUX/UNIX commands in combination with GMT. GMT is an open source collection of tools for manipulating geographic data sets. Additional information about GMT can be found at: http://www.soest.hawaii.edu/gmt and additional information about the multibeam data processing is recorded in the cruise metadata.
Depth values are real values based on the average of the soundings that fell within the extracted grid cells. The number of soundings per grid cell range from >1000 soundings in shallow depths to as few as 20 soundings in deeper areas. A total error budget for these data have not been developed. Therefore, the accuracy of depth measurements should be considered to be within 1 meter.
none
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.
These data can be downloaded as either a 2-D binary netCDF raster grid or an ArcGIS ASCII text file. The netCDF grid is the default grid file format used by GMT (Generic Mapping Tools), which created this file. More information can be located at http://www.soest.hawaii.edu/gmt/and http://www.unidata.ucar.edu/software/netcdf/. The Arc ASCII file, for use in ESRI's (http://www.esri.com) GIS software, can be converted to an Arc Raster Grid using ArcToolbox ASCII to Raster conversion tool.
