U.S. Geological Survey
20161122
Single-Beam Bathymetry Data 30-meter DEM Collected in 2015 from Grand Bay, Alabama/Mississippi
raster digital data
https://doi.org/10.5066/F7NP22M2
Nancy T. DeWitt
Chelsea A. Stalk
Christopher G. Smith
Stanley D. Locker
Jake J. Fredericks
Terrance A. McClosky
Cathryn J. Wheaton
Unpublished Material
Single-Beam Bathymetry Data Collected in 2015 from Grand Bay, Alabama/Mississippi
multimedia presentation
U.S. Geological Survey Data Series
1070
St. Petersburg, FL
U.S. Geological Survey
https://doi.org/10.3133/ds1070
As part of the Sea level and Storm Impacts on Estuarine Environments and Shorelines project (SSIEES), scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center conducted a single-beam bathymetry survey within the estuarine, open bay and tidal creek environments of Grand Bay Alabama/Mississippi, in May-June 2015. The goal of the SSIEES project is to assess the physical controls of sediment and material exchange between wetlands and estuarine environments along the northern Gulf of Mexico, specifically Grand Bay MS/AL and Vermilion Bay, Louisiana, as well as along the US east coast in Chincoteague Bay Virginia/Maryland. The data described in this report will provide baseline bathymetric information for future research investigating wetland/marsh evolution, sediment transport, recent and long term geomorphic change, and will support modeling of future changes in response to restoration and storm impacts. The survey area encompasses more than 40 square kilometers (km2) of Grand Bay?s incorporated waters. This data release archives processed single-beam bathymetry data, collected from May 28-June 3, 2015 (USGS Field Activity Number 2015-315-FA). Geographic information system data products include: a 10 and 30-meter cell size interpolated bathymetry grid, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System (FACS) logs, and formal Federal Geographic Data Committee (FGDC) metadata.
This 30-meter cell size digital elevation model is an interpretive product that was derived from the processed single-beam bathymetry data collected in May-June 2015 within Grand Bay Alabama/Mississippi.
This record serves as a comprehensive archive for the final Digital Elevation Model (DEM) created by the use of all single-beam bathymetry data collected under the FAN (2015-315-FA) which encompasses data from 2 separate survey platforms; RV Shark (15CCT04), and RV Chum (15CCT05). The single-beam bathymetry corrected position was obtained through post processing of the base station data to the concurrent rover data. All datasets were transformed from their initial datum International Terrestrial Reference Frame of 2000 (ITRF00) to NAD83 using GEOID12A as well as NAD83 Mean Low Lower Water (MLLW) (NOAA NGS VDatum software 3.2 - http://vdatum.noaa.gov/). The Final x,y,x position point data was gridded at a 30-meter cell size resolution to create the digital elevation model which represents elevations from -0.01 to -3.62 meters.
20150528
20150603
ground condition
none
-88.412969
-88.311205
30.409530
30.340547
ISO 19115 Topic Category
elevation
geoscientific Information
imageryBaseMapsEarthCover
oceans
USGS Thesaurus
marine geology
geophysics
bathymetry
None
marine geology
bathymetry
single beam
CARIS
HIPS and SIPS
hydrography
geophysical
U.S. Geological Survey
USGS
Sea level and Storm Impacts on Estuarine Environments and Shorelines project
SSIEES
St. Petersburg Coastal and Marine Science Center
SPCMSC
Coastal Change and Transport
Single-beam Bathymetry
2015-315-FA
Digital Elevation Model
Geographic Names Information System (GNIS)
Grand Bay
Gulf of Mexico
Mississippi
Alabama
None
None
U.S. Geological Survey
Nancy T. DeWitt
Geologist
Mailing and physical
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8000
ndewitt.gov
U.S. Geological Survey, Coastal and Marine Geology Program, St. Petersburg Coastal and Marine Science Center (SPCMSC)
Microsoft Windows 7 Service Pack 1; Esri ArcGIS 10.2 Service Pack 1 Build 3143; Esri ArcCatalog 10.2 Build 3143
The accuracy of the data is determined during data collection. Methods are employed to maintain data collection consistency aboard various platforms. During mobilization, each piece of equipment is isolated to obtain internal and external offset measurements with respect to the survey platform. All the critical measurements are recorded manually and digitally and entered into their respective programs for calibration, acquisition, and post processing. Each system has a dedicated computer, and efforts are made to utilize the same equipment and software versions on all systems. However, upgrades and changes occur and require additional setup, measurements, and notation. DGPS is always implemented for navigational accuracy as a post-processing step. These bathymetric data have not been independently verified for accuracy, rather verified as a whole product.
The single beam bathymetry data were collected during one research cruise in May 28-June 3, 2015 (2015-315-FA). Refer to the online Data Series linkage for field logs, vessel platform descriptions, and other survey information. This dataset was created to provide a post-processed bathymetric grid from the data and accompanying x,y,z deliverables. The DEM is 30-meter; data gaps between acquisition tracklines are predicted values generated by the gridding algorithm - natural neighbors.
This dataset is considered complete for the information presented, as described in the abstract section. Users are advised to read the rest of the metadata record carefully for additional details.
The stated horizontal accuracy of the Ashtech Proflex 500 and 800 GPS receivers used during single-beam bathymetry acquisition is reported by Ashtech as +/-10 mm for Kinematic surveying.
-0.00000134 to +0.00000134
latitude decimal degrees
-0.0000019 to +0.0000019
longitude decimal degrees
The stated vertical accuracy of the Ashtech Proflex 500 and 800 GPS units used during single-beam bathymetry acquisition is +/- 10 mm. The vertical accuracy for the Odom Echtrac_CV100 unit used on all survey platforms is 0.01 m +/- 0.1% of the depth value.
DGPS Navigation Processing: The Geographic Positioning System (GPS) base stations were occupied by USGS personnel for the purpose of this survey. Bench mark B166 was located to the north-north west of the survey area near the railroad tracks at the entrance of the Grand Bay National Estuarine Research Reserve (GBNERR), 189A was located north-north west of the survey area at the boat launch location used for this survey). The base stations were equipped with Ashtech Proflex GPS Receivers recording 12-channel full-carrier-phase positioning signals (L1/L2) from satellites via Thales choke-ring antennas, recording at 0.1 seconds (s). GPS instrumentation was duplicated on both survey vessels (rovers); however, an Ashtech Global Navigation Satellite Systems (GNSS) antenna was used instead of Choke-ring antennas. The base receivers and rover receivers recorded positions concurrently at all times throughout the survey. Rovers RV Shark and RV Chum recorded data every 0.1 s throughout the survey. The coordinate values for each of the GPS base stations (B166,189A) are the time-weighted average of values obtained from the National Geodetic Survey's (NGS) On-Line Positioning User Service (OPUS). All base station sessions of recorded data are decimated to 30-seconds (s), and then submitted to OPUS via the online service. All solutions are then returned to the user and entered into a spreadsheet where time-weighted ellipsoid values are calculated for each station, for the entire occupation. Any individual ellipsoid value that falls outside three standard deviations for the entire occupation was excluded and the final coordinate values were then determined. The final base station coordinates were imported into GrafNav version 8.5 (Waypoint Product Group) and the kinematic GPS data from the survey vessel were post-processed to the concurrent GPS data from the base stations. During processing, steps were taken to ensure that the trajectories between the base and rover were clean and resulted in fixed positions. By analyzing the graphs, trajectory maps, and processing logs that GrafNav produces for each GPS session, GPS data from satellites flagged by the program as having poor health or satellite time segments with cycle slips were excluded, and the satellite elevation mask angle was adjusted to improve the position solutions, when necessary. The final, differentially corrected, precise DGPS positions were computed at their respective time intervals (0.1-s for 15CCT04, 15CCT05), and then exported in ASCII text format. The file was then used to replace the uncorrected real-time rover positions recorded during acquisition. The GPS data were processed and exported in the World Geodetic System of 1984 (WGS84) (G1150) geodetic datum UTM zone 16N.
2015
U.S. Geological Survey
Nancy T. DeWitt
Geologist
mailing and physical
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8000
ndewitt@usgs.gov
Single Bream Processing: The raw HYPACK? data files were imported into CARIS HIPS and SIPS? (Hydrographic Information Processing System and Sonar Information Processing System) version 9.0.17. The corrected DGPS positions exported from GrafNav were imported into CARIS using the generic data parser tool. After parsing, the navigation data was scanned using the Navigation Editor allowing the user to view multiple types of plots including trackline orientation, timing, and course direction. This check verifies if the parsed data corresponds to the processed DGPS. Next, Speed of Sound Profile (SVP) casts were entered, and edited, using the SVP editor tool, and then applied as nearest in distance within time. All soundings are referenced to the ellipsoid during processing. This involved a step in CARIS to compute the GPS tide. The GPS tide represents the ellipsoidal surface. GPS tide and GPS height are then compared against each other to ensure correct computation by the program and applied GPS antenna height provided in the vessel file. All bathymetric data components including position, depth, GPS tide, and Speed of Sound (SOS), were then merged and geometrically corrected in CARIS to produce processed x,y,z point data. Once merged the dataset is reviewed for erroneous points using the Single Beam Editor. The points that are visually obvious are often related to cavitation in the water column obscuring the fathometer signal, tight turns at the marsh face affecting the tracking of the incoming GPS signal, and/or false readings due to general equipment issues. Data showing these issues are either discarded or adjusted to surrounding sounding depths. Also, data points in areas of extremely shallow water (0.30 m to 0.50 m) such as on shoals or within seagrass beds were reviewed against the surrounding data for overall consistency. Finally, a Bathymetry with Associated Statistical Error (BASE) surface was created. Using the Subset Editor, the BASE surface was used as a color coded guide to pinpoint crossings that are visually offset from one another. If an offset was identified, it was further examined and was reprocessed if necessary. The geometrically corrected point data are then exported as an x,y,z ASCII text file referenced to WGS84 (G1150), equivalent to ITRF00, UTM 16, and ellipsoid height, in meters. The combined single-beam bathymetry datasets (15CCT04 and 15CCT05) consists of 3,844,122 x,y,z data points with an ellipsoidal height range of -33.364 m to -29.531 m.
2015
Grand_Bay_2015_SBB_Level_05_ITRF00.txt
U.S. Geological Survey
Nancy T. Dewitt
Geologist
mailing and physical
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8000
cstalk@usgs.gov
Quality Control and Quality Assurance (QA/QC) and Datum transformation: All Single-beam data found in the ASCII exported from CARIS were imported into Esri ArcMap version 10.2, where a shapefile of the individual data points (x,y,z) was created and plotted in 0.5-m color coded intervals. First all data were visually scanned for any obvious outliers or problems. Then, the data were run through an in-house script created in Visual Basic (Crossing program Version 3.2). The script was created for the purpose of evaluating elevation differences at the intersection of crossing tracklines by calculating the elevation difference between points at each intersection using an inverse distance weighting equation. Elevation values at line crossings should not differ by more than the combined instrument acquisition error (per manufacturer specified accuracies). GPS cycle slips, stormy weather conditions, and rough sea surface states can contribute to poor data quality. If discrepancies that exceed the acceptable error threshold were found, then the line in error was either removed or statically adjusted. The script was run on all vessel point data first on a vessel by vessel basis and then run a final time with both vessels collectively by use of a merged shape file with all point data (Grand_Bay_2015_SBB_Level_05_xxx_ITRF00). Once all data were found to be final, the single-beam bathymetric data were transformed horizontally and vertically from their data acquisition datum WGS84 (ITRF00) to the North American Datum of 1983 (NAD83) reference frame using the National Geodetic Survey (NGS) geoid model of 2012A (GEOID12A) as well as North American Datum of 1983 (NAD83) Mean Lower Low Water, using the transformation software VDatum version 3.2. The MLLW x,y,z data points were written into a ASCII format and considered to be the final values.
2015-315-FA_SBB_Level_03_xxx_ITRF00.txt
2015
Grand_Bay_2015_SBB_Level_05_xxx_NAD83_NAVD88_GEIOD12A.txt
Grand_Bay_2015_SBB_Level_05_xxx_NAD83_UTM16N_MLLW.txt
U.S. Geological Survey
Nancy T. DeWitt
Geologist
mailing and physical
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8000
ndewitt@usgs.gov
Gridding Bathymetric data and computing grid error: The single-beam soundings were imported into ESRI?s ArcMap version 10.2 and gridded using Spatial Analyst tools "create TIN," "TIN to raster," and "extract by raster mask." First a bounding polygon representing the extent of survey tracklines was created and converted into a raster mask using the ArcGIS "polygon to raster" tool. Next, the final point data were created into a TIN using the "create TIN" and then the data were converted into a raster DEM by use of the "TIN to raster tool" using the natural neighbor function with a cell size of 30 m. Finally the interpolated DEM is clipped to the survey extent by use of the "extract by mask" tool using the raster mask created first in this process. The final product is a DEM of the entire survey extent. The grid range values were from -0.01 m maximum to -3.62 m minimum. In order to evaluate how well the final DEM represents the final sounding data both spatially and quantitatively a comparison of the DEM versus the sounding (x,y,z point data) was plotted in ArcGIS by use of the ?Extract values by points? spatial analyst tool. This tool extracts the value represented by the underlying grid and compares it to that of the overlying point data. By use of the generated shape file and associated attribute table, the root mean square (RMS) error, quantified as the difference between the measured depth and the grid depth values, was calculated. The overall RMS Error in meters is 0.07.
Grand_Bay_2015_SBB_NAD83_MLLW.txt
2015
Grand_Bay_2015_NAD83_MLLW_30m_DEM.tif
U.S. Geological Survey
Nanacy T. DeWitt
Geologist
mailing and physical
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8000
ndewitt@usgs.gov
Raster
Grid Cell
251
323
1
Universal Transverse Mercator
16
0.9996
-87
0.0
500000.0
0.0
row and column
30
30
meter
NAD83 North American Datum 1983
MLLW
6378137.0
298.257222101
MLLW
0.10
meter
Implicit coordinate
U.S. Geological Survey
Nancy T. Dewitt
Geologist
mailing and physical
600 4th Street South
St. Petersburg
FL
33701
USA
(727) 502-8000
ndewitt@usgs.gov
Grand_Bay_2015_NAD83_MLLW_30m_DEM.tif
This publication was prepared by an agency of the United States Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
GeoTIFF
ZIP
1.91
https://coastal.er.usgs.gov/data-release/doi-F7NP22M2/data/Grand_Bay_2015_NAD83_MLLW_30m_DEM.zip
none
The raster contained in the .zip file is available as GeoTIFF. To utilize this data, the user must have a GIS software package capable of reading .tif format.
20180327
Cherokee Nation Technologies/U.S. Geological Survey
Chelsea A Stalk
Researcher I
mailing and physical
600 4th Street South
St. Petersburg
FL
33701
USA
727-502-8000
cstalk@usgs.gov
FGDC Content Standard for Digital Geospatial Metadata
FGDC-STD-001-1998
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution.
None
Unclassified
None