Gridded bathymetry from Apra Harbor, Guam U.S. Territory. The netCDF and Arc ASCII grids include multibeam bathymetry from the Reson SeaBat 8125 multibeam sonar collected in 2008 by the NOAA Office of Coast Survey and the United States Navy Fleet Survey Team. The sonar frequency is 455 kHz and the data are gridded at 1 m resolution. The data served here were extracted from a Caris project provided by OCS and converted to netCDF and Arc ASCII grids by the NOAA Coral Reef Ecosystem Division.
These data were collected in response to a request by the USN for a cooperative modern hydrographic survey with NOAA to provide contemporary hydrographic data to update the nautical charts in the area. The USN plans to use Apra Harbor, Guam as a primary port-of-call. These data will support safe navigation for the USN fleet in Apra Harbor by providing IHO Order 1 hydrography. They will also aid in ongoing habitat mapping efforts by NOAA PIFSC CRED. 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.
Survey data were acquired by the United States Navy (USN) Fleet Survey Team (FST) with Survey Vessel Swamp Fox. A Reson 8125 multibeam echosounder was mounted from an arm on the port side of the vessel. The Klein 3000 Side Scan Sonar is operated in the stern-towed configuration. Additional detailed information on data acquisition, equipment configuration, and corrections can be found in the Data Acquisition and Processing Report (DAPR), SWAMPFOX_DAPR_2008.pdf, that can be accessed at: www.soest.hawaii.edu/pibhmc and is included in the ZIP file containing the bathymetry grids. Vertical_Coordinate_System_Definition Depth_System_Definition
ground condition
These data are not to be used for navigation purposes. Please acknowledge NOAA Pacific Islands Fisheries Science Center, the Joint Institute for Marine and Atmospheric Research (JIMAR) University of Hawaii, the NOAA Office of Coast Survey, and the USN Fleet Survey Team as the sources of this information.
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NMFS/PIFSC/CRED
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https://www.soest.hawaii.edu/pibhmc/CNMI_images/apra_bty_1m_445.jpg
NOAA OCS, USN FST, 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: see DAPR Horizontal position accuracy: see DAPR
see DAPR Raw sounding resolution: Variable
Refer to the the Data Acquisition and Processing Report (DAPR) that can be accessed at: www.soest.hawaii.edu/pibhmc and is included in the ZIP file containing the bathymetry grids for detailed information on the bathymetry data processing steps.
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 is reported in the DAPR.
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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.
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 https://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.
