Gridded bathymetry (5m) of the shelf environment of Nihoa Island, Hawaii, USA. This netCDF grid includes multibeam bathymetry from the Simrad EM120, Simrad EM1002, Simrad EM300, and Simrad EM3002d multibeam sonars collected as of December 2006 by the NOAA Coral Reef Ecosystem Division in depths between 20 and 500 meters.
The netCDF grid was 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, a 218' United States National Oceanographic and Atmospheric Administration 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 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. Specific equipment configurations are documented in cruise metadata from the following cruises: HI0501, HI0612. 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 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/NWHI_images/Nihoa_5m_500.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: Variable, see process description Horizontal position accuracy: Variable, see process description
Variable, see process description Raw sounding resolution: Variable, see process description
Multibeam swath files are acquired 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 in SABER and area based editing is performed. The edited PFM is then exported as X,Y,Z points with a defined grid cell size and the points are combined with X,Y,Z IKONOS estimated depth points. The resulting X,Y,Z data are then gridded using xyz2grd, a Generic Mapping Tools (GMT) algorithm that converts an ASCII or binary table to a netCDF grid file format. GMT is an open source collection of tools for manipulating geographic data sets. Grid nodes with more than one value are set to the average value and unconstrained nodes are set to NaN. Finally, the netCDF grid is clipped at a depth that minimizes data gaps for the specified grid cell size and then converted to an ArcGIS ASCII file format using LINUX/UNIX commands in combination with GMT. Additional information about GMT can be found at: 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 this survey has 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.
This file is formatted as a 2-D binary netCDF grid file. This is the default grid file format used by GMT (Generic Mapping Tools). More information can be found at http://www.soest.hawaii.edu/gmt/ and http://www.unidata.ucar.edu/software/netcdf/.
