Data Management Plan

These data were collected under a cooperative mapping program between the U.S. Geological Survey (USGS), the National Oceanic and Atmospheric Administration Office for Coastal Management (NOAA\OCM), and the Apalachicola National Estuarine Research Reserve (NERR). The primary objectives of this program were to collect marine geophysical data to develop a suite of seafloor maps to better define the extent of oyster habitats, the overall seafloor geology of the bay and provide updated information for management of this resource. In addition to their value for management of the bay's oyster resources, the maps also provide a geologic framework for scientific research and the public.

High-resolution bathymetry, backscatter intensity, and seismic profile data were collected over 230 square kilometers of the floor of the bay. The study focused on Apalachicola Bay and Western St. George Sound portions of the estuary mostly in depths > 2.0 meters.

Original contact information:

Contact Name: Brian Andrews

Contact Org: U.S. Geological Survey

Title: Geographer

Phone: 508-548-8700 x2348

Email: bandrews@usgs.gov

Process Steps:

• 2006-10-01 00:00:00 - Bathymetric data were corrected for variations in the speed of sound throughout the water column; sound velocity profiles were acquired throughout the survey area using an Applied MicroSystems SVPlus Sound Velocimeter. These data were downloaded and reformatted to the required format needed for use within University of New Brunswick's Ocean Mapping Group (OMG) SwathEd multibeam processing software. The raw Submetrix 2000 Series data were "unraveled" and reformatted into the OMG format. This process creates several files on disk: 1) bathymetric soundings 2) raw sidescan backscatter 3) navigation 4) parameter files describing the configuration of the system (i.e. offsets between motion reference unit and GPS antenna, etc). This process also incorporates the sound velocity profiles in order to properly trace the rays given the structure of the water column.
• 2006-10-01 00:00:00 - The OMG formatted bathymetric data were then graphically edited using the SwathEd multibeam processing software. This step enabled editing on a "ping-by-ping" basis, both in the across- and along-track dimension. Spurious or erroneous data were removed. The navigation data were also graphically examined for each line of data.
• 2006-10-01 00:00:00 - Soundings were corrected to mean lower low water (MLLW) using high-resolution Real-Time Kinematic Global Positioning System (RTKGPS) measurements. The one second RTK data were smoothed in MatLab using a 3rd order polynomial and then merged with each line file in SwathEd.
• 2006-10-01 00:00:00 - Soundings data were gridded using the weigh_grid routines from SwathEd. Soundings were corrected to mean lower low water during the weigh_grid operation using the real time kinematic differential global positioning navigation files. The final weigh_grid parameters used were: weigh_grid -omg -coeffs -butter -lambda 5 -cutoff 20 Max_incidence angle was not used on most lines to allow usage of bathymetry data points from a broader section of the swath. Only lines from rough days, when the vessel heave was large, were gridded with a small incidence angle to maximize the good data from adjacent lanes and reduce the noisy data.
• 2006-10-01 00:00:00 - Final soundings were gridded to a 5m grid cell resolution using SwathEd weigh_grid command and the following gridding parameters: weigh_grid -omg -coeffs -butter -power 2 -lambda 1 -cutoff 4 -max_incidence 60 A 5m grid cell size reduced the number of points and a max_incidence of 60 degrees was used to remove the outer soundings which tended to be noisy.
• 2006-10-01 00:00:00 - The final grid in SwathEd OMG format was imported directly into IVS DMagic software producing a .geo, .dtm, and .shade file. The dtm file was exported to an x,y,z comma delimited file.
• 2006-10-01 00:00:00 - The comma-delimited x,y,z file of bathymetry was added to ArcMap as an event theme and converted to a point feature class. Two separate x,y,z files and feature classes were processed; one for Apalachicola Bay, and one for St. George Sound.
• 2006-10-01 00:00:00 - The remaining geoprocessing steps were completed using one model developed in ArcGIS Modelbuilder. The Model is included in the geodatabase distributed with the Open-File Report. Each of the processing steps used to Create the Model for St. George Sound are described below. The same processing steps were used to create a second Model for Apalachicola Bay using the same steps. Created empty TIN and added the x,y,z points using the geoprocessing history below: Create TIN *Date: 20061027 *Time: 113410 *Tool location: C:\Program Files\ArcGIS\ArcToolbox\Toolboxes\3D Analyst Tools.tbx\CreateTin *Command issued: CreateTin D:\GIS\FL\rafa06001\ArcGIS\Bathy\BathInterp\Tin\StGTin "PROJCS['WGS_1984_UTM_Zone_16N',GEOGCS['GCS_WGS_1984',DATUM['D_WGS_1984',SPHEROID['WGS_1984',6378137.0,298.257223563]],PRIMEM['Greenwich',0.0],UNIT['Degree',0.0174532925199433]],PROJECTION['Transverse_Mercator'],PARAMETER['False_Easting',500000.0],PARAMETER['False_Northing',0.0],PARAMETER['Central_Meridian',-87.0],PARAMETER['Scale_Factor',0.9996],PARAMETER['Latitude_Of_Origin',0.0],UNIT['Meter',1.0]];-10000 -10000 100000;0 100000;0 100000"
• 2006-10-01 00:00:00 - Added 5m xyz points to TIN See geoprocessing history below: Process: *Process name: Edit TIN *Date: 20061027 *Time: 113535 *Tool location: C:\Program Files\ArcGIS\ArcToolbox\Toolboxes\3D Analyst Tools.tbx\EditTin *Command issued: EditTin D:\GIS\FL\rafa06001\ArcGIS\Bathy\BathInterp\Tin\stgtin "StG_5mc_xyz depth masspoints false;BathClip <None> <None> hardclip false" D:\GIS\FL\rafa06001\ArcGIS\Bathy\BathInterp\Tin\stgtin
• 2007-01-01 00:00:00 - Converted Tin to Raster using Natural Neighbors using floating point and natural neighbors options. Cells size was set at 25m.
• 2007-01-01 00:00:00 - Output Raster was clipped to a polygon boundary delineating the extent of bathymetric data.
• 2007-01-01 00:00:00 - The clipped 25m bathymetric grid was smoothed with a 3x3 low-pass filter.
• 2007-01-01 00:00:00 - Individual 25m smoothed grids of Apalachicola Bay and St. George Sound were merged together to make one grid for both areas.

Data can be downloaded via the World Wide Web (WWW);