Metadata: Identification_Information: Citation: Citation_Information: Originator: U.S. Geological Survey Publication_Date: 2009 Title: Hillshaded relief produced from bathymetric data collected by the U.S. Geological Survey offshore of the Chandeleur Islands, LA, 2006-2007 (BATHY_HILLSH.ASC, ESRI ASCII GRID) Edition: 1.0 Geospatial_Data_Presentation_Form: raster digital data Series_Information: Series_Name: Open-File Report Issue_Identification: 2008-1195 Publication_Information: Publication_Place: Woods Hole Coastal and Marine Science Center, Woods Hole, MA Publisher: U.S. Geological Survey, Coastal and Marine Geology Program Online_Linkage: https://doi.org/10.3133/ofr20081195 Online_Linkage: http://pubs.usgs.gov/of/2008/1195/GIS_catalog/Bathy/bathy_hillsh.zip Larger_Work_Citation: Citation_Information: Originator: Wayne E. Baldwin Originator: Elizabeth A. Pendleton Originator: David C. Twichell Publication_Date: 2009 Title: Geophysical Data from offshore of the Chandeleur Islands, Eastern Mississippi Delta Edition: 1.0 Series_Information: Series_Name: Open-File Report Issue_Identification: 2008-1195 Publication_Information: Publication_Place: Reston, VA Publisher: U.S. Geological Survey Online_Linkage: http://pubs.usgs.gov/of/2008/1195/ Description: Abstract: In 2006 and 2007, the U.S. Geological Survey, in partnership with Louisiana Department of Natural Resources and the University of New Orleans, conducted geologic mapping to characterize the sea floor and shallow subsurface stratigraphy offshore of the Chandeleur Islands in Eastern Louisiana. The mapping was carried out during two cruises on the R/V Acadiana. Data were acquired with the following equipment: an SEA Ltd SwathPlus interferometric sonar (234 kHz), Klein 3000 dual frequency sidescan sonar, and an Edgetech 512i chirp subbottom profiling system. The long-term goal of this mapping effort is to produce high-quality geologic maps and geophysical interpretations that can be utilized to investigate the impact of Hurricane Katrina in 2005 and to identify sand resources within the region. Purpose: This grid represents a hillshade of approximately 470 square km of bathymetric data that were collected in 2006 and 2007. These data are used to define the sea-floor morphology offshore of the Chandeleur Islands in Eastern Louisiana. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 20060708 Ending_Date: 20070622 Currentness_Reference: ground condition of two separate cruises - 20060708 to 20060719 and 20070610 to 20070622 Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -89.298264 East_Bounding_Coordinate: -88.751860 North_Bounding_Coordinate: 30.117223 South_Bounding_Coordinate: 29.382588 Keywords: Theme: Theme_Keyword_Thesaurus: USGS Metadata Identifier Theme_Keyword: USGS:4e176d5d-29e0-4768-bb73-9bda02208e15 Theme: Theme_Keyword_Thesaurus: None Theme_Keyword: U.S. Geological Survey Theme_Keyword: USGS Theme_Keyword: Woods Hole Science Center Theme_Keyword: WHSC Theme_Keyword: Coastal and Marine Geology Program Theme_Keyword: CMGP Theme_Keyword: bathymetry Theme_Keyword: swath bathymetry Theme_Keyword: interferometry Theme_Keyword: sea-floor morphology Theme_Keyword: ArcRaster grid Theme_Keyword: hillshade Theme_Keyword: WHSC field activity serial number 06015 Theme_Keyword: WHSC field activity serial number 07007 Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Category Theme_Keyword: oceans Theme_Keyword: elevation Theme_Keyword: imageryBaseMapsEarthCover Theme_Keyword: geoscientificInformation Theme: Theme_Keyword_Thesaurus: USGS Thesaurus Theme_Keyword: sea-floor characteristics Theme_Keyword: marine geophysics Theme_Keyword: computational methods Theme_Keyword: geospatial datasets Theme_Keyword: interferometric sonar Place: Place_Keyword_Thesaurus: None Place_Keyword: Louisiana Place_Keyword: Chandeleur Islands Place_Keyword: Breton Island Place_Keyword: Gosier Island Place_Keyword: Curlew Island Place_Keyword: Mississippi River Gulf Outlet Place_Keyword: New Harbor Islands Place_Keyword: North Islands Place_Keyword: North-Central Gulf Coast Place_Keyword: United States Place_Keyword: Gulf of Mexico Place_Keyword: MRGO Access_Constraints: None Use_Constraints: These data are NOT to be used for navigation. Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: David C. Twichell Contact_Organization: U.S. Geological Survey Contact_Position: Oceanographer Contact_Address: Address_Type: mailing and physical address Address: 384 Woods Hole Rd. City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Contact_Voice_Telephone: (508) 548-8700x2266 Contact_Facsimile_Telephone: (508) 457-2310 Contact_Electronic_Mail_Address: dtwichell@usgs.gov Browse_Graphic: Browse_Graphic_File_Name: http://pubs.usgs.gov/of/2008/1195/images/bathy_grd.jpg Browse_Graphic_File_Description: color coded image of bathymetry Browse_Graphic_File_Type: JPEG Native_Data_Set_Environment: Microsoft Windows XP Professional x64 Edition Version 2003 Service Pack 2; ESRI ArcCatalog 9.2.4.1420 Cross_Reference: Citation_Information: Originator: Craig Martin Publication_Date: unpublished material Title: NOAA/NOS Hydrographic Planning Team (HPT) tide zone model Online_Linkage: http://www.tidesandcurrents.noaa.gov/hydro.html Cross_Reference: Citation_Information: Originator: Jonathan Beaudoin Publication_Date: 2002 Title: Hitchhiker's Guide to SwathEd... Publication_Information: Publication_Place: Fredericton, New Brunswick, CA Publisher: Ocean Mapping Group - University of New Brunswick Online_Linkage: http://www.omg.unb.ca/~jonnyb/processing/definitive_swathed/index.html Cross_Reference: Citation_Information: Originator: J. F. Luis Publication_Date: 2007 Title: Mirone: A multi-purpose tool for exploring grid data. Geospatial_Data_Presentation_Form: document Series_Information: Series_Name: Computers & Geosciences Issue_Identification: 33 Other_Citation_Details: Original online link that no longer seems valid: http://w3.ualg.pt/~jluis/mirone/mirone_Refs.htm Cross_Reference: Citation_Information: Originator: P. Wessel and W. H. F. Smith Publication_Date: 1998 Title: New, improved version of the Generic Mapping Tools released Series_Information: Series_Name: EOS Transactions Issue_Identification: 79 Publication_Information: Publication_Place: Washington, D.C. Publisher: American Geophyscial Union Online_Linkage: http://gmt.soest.hawaii.edu/ Data_Quality_Information: Logical_Consistency_Report: Information unavailable from original metadata. Completeness_Report: All shore parallel survey lines were incorporated. Tie (shore perpendicular) lines were not used in grid generation. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: These data were navigated with a Differential Global Positioning System (DGPS), which is assumed to be accurate to +/- 1 to 2 meters, horizontally. Unless noted, all DGPS data are referenced to WGS84, and distance between sidemounted interferometric sonar and GPS antennae are corrected. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: The theoretical vertical resolution of the SEA Ltd SwathPlus interferometric sonar is 1 % of water depth, approximately 0.1 m within the study area. In 2006, ship motion was recorded with a TSS DMS 2-05 and used to correct for vessel roll, pitch, heave, and yaw. In 2007, the Octopus F180 Attitude and Positioning system was used to correct ship motion. Tidal offsets were corrected with a NOAA tide zone model and referenced to mean lower low water. Errors associated with the tidal zone model could be less than or equal to the tidal range for this area which is ~0.4 m. The gridding algorithm and cell size used on these data could introduce errors as great as 3 m along the edges of the MRGO channel. Gridding-induced errors are likely much smaller (< 0.5 m) for most of the study area where slopes are less that 10 degrees. Changes in ship draft due to water and fuel usage were not considered. Lineage: Source_Information: Source_Citation: Citation_Information: Originator: U.S. Geological Survey Publication_Date: Unpublished material Title: Bathymetry data collection Type_of_Source_Media: disc Source_Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 20060708 Ending_Date: 20070622 Source_Currentness_Reference: ground condition of two separate cruises - 20060708 to 20060719 and 20070610 to 20070622 Source_Citation_Abbreviation: raw bathy data Source_Contribution: Data acquisition at sea (2006; 2007): These bathymetric data were collected with a SEA Ltd Swathplus interferometric sonar (234 kHz) mounted on the portside of the R/V Acadiana of Loreauville, LA. The data were acquired during 2 cruises with SwathPlus Software (version: none) in July 2006 and June of 2007. Data were collected along tracklines spaced 100 to 125 m apart in the shore parallel direction and about 1 km apart in the shore perpendicular direction at a speed of 1.5 to 2.5 m/s. Sound velocity profiles were acquired approximately every 6 to 8 hours during the surveys using an Applied MicroSystems SVPlus Sound Velocimeter. Process_Step: Process_Description: A suite of processing software called SwathEd (version: none) developed by the University of New Brunswick - Ocean Mapping Group () was used to process, edit, and archive the bathymetric soundings after collection (Beaudoin, 2002). The processing and editing steps were: 1. The raw Submetrix 2000 Series data were 'unraveled'. This process creates several files on disk: bathymetric soundings, raw sidescan-sonar backscatter, navigation, parameter files describing the configuration of the system (i.e. offsets between motion reference unit and GPS antenna, etc), and sound velocity at the transducer and sound velocity profiler information. 2. The navigation data were edited on screen using the SwathEd routine 'jview' to remove undesirable points, including turns at the ends of survey lines. Jview also rejects stray GPS fixes outside of the survey area - a parameter set by the operator. 3. The soundings for each trackline were edited using SwathEd. Blocks of data across and along a trackline can be displayed in a SwathEd window. Anomalous points were identified by comparison to other points (i.e. standard deviation of a swath section) and removed in a process known as 'fluffing'. 4. The bathymetric soundings from each processed data file were mapped onto a Mercator grid (UTM zone 16N) from the original acquired projection which was geographic WGS84 using weigh_grid with grid nodes spaced at 5 meters. The weigh_grid program creates a Digital Terrain Model (DTM) by summing up the weighted contributions of all the provided data into the DTM. The weighted contributions only extend to a user defined region around the true location of the estimated depth value. Processing took place in 2006 and 2007. Process_Date: 2007 Process_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Wayne E. Baldwin Contact_Organization: U.S. Geological Survey Contact_Position: Geologist Contact_Address: Address_Type: mailing and physical address Address: 384 Woods Hole Rd. City: Woods Hole State_or_Province: MA Postal_Code: 02543-1598 Contact_Voice_Telephone: (508) 548-8700x2226 Contact_Facsimile_Telephone: (508) 457-2310 Contact_Electronic_Mail_Address: wbaldwin@usgs.gov Process_Step: Process_Description: The data were corrected for errors in soundings due to sound refraction, caused by variations in sound velocity profile, using the SwathEd refraction tool (version: none). These artifacts can be recognized in a cross-swath profile of a relatively flat patch of sea floor. When viewing the swath data across a profile, the sea floor will appear to have a "frown" or "smile" when in fact the data should be flat across the profile. Insufficient and/or erroneous sound velocity information, which is usually due to too widely spaced or non-existent velocity profiles within an area, results in an under or over-estimate of water depth which increases with distance from the center of the swath. For a discussion of how this effect can be recognized in a swath bathymetric data file, see . 2. The bathymetric data were corrected to mean lower low water using discrete tidal-zoning models (DTZ) developed by NOAA/NOS's Hdrographic Planning Team (Martin, personal communication, 2006; 2007) (