U.S. Geological Survey, 2007, APBAY25HS- 25m Hillshaded Bathymetric ArcRaster Grid of Apalachicola Bay and St. George Sound, FL: Open-File Report 2006-1381, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, Massachusetts.This is part of the following larger work.
Twichell, David C. , Andrews, Brian D. , Edmiston, H. Lee , and Stevenson, William R. , 2007, Geophysical Mapping of oyster habitats in a shallow estuary; Apalachicola Bay, Florida: Open-File Report 2006-1381, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, Massachusetts.
This is a Raster data set. It contains the following raster data types:
Planar coordinates are encoded using row and column
Abscissae (x-coordinates) are specified to the nearest 25.000000
Ordinates (y-coordinates) are specified to the nearest 25.000000
Planar coordinates are specified in meters
The horizontal datum used is D_WGS_1984.
The ellipsoid used is WGS_1984.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.257224.
Sequential unique whole numbers that are automatically generated.
508-548-8700 x2348 (voice)
The purpose of this dataset is to produce a bathymetric hillshade grid from swath bathymetry that was collected within the survey boundary in St. George Sound and Apalachicola Bay.
U.S. Geological Survey, 2007, APBAYBATH25M - 25m Bathymetric Model of Apalachicola Bay and St. George Sound, Florida: Open-File Report 2006-1381, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, Massachusetts.This is part of the following larger work.
Twichell, David C. , Andrews, Brian D. , Edmiston, H. Lee , and Stevenson, William R. , 2007, Geophysical Mapping of oyster habitats in a shallow estuary; Apalachicola Bay, Florida.
Person who carried out this activity:
508-548-8700 x 2348 (voice)
Data sources produced in this process:
DGPS is assumed to be accurate within 1-2 meters. Standard GPS is assumed accurate within 5-10 meters. 99% of the positional data is DGPS. Unless noted, all GPS/DGPS data is referenced to WGS84 (NAD83). The configuration of the fathometer is as follows: The fathometer is mounted on a pole at the bow of the R/V RAFAEL. Offset between the fathometer pole and GPS antenna is measured. On ASV IRIS, the seismic profiler from which single-beam bathymetry measurements were collected was directly below the GPS antenna. No measurements were taken of ship's pitch, yaw, heave, or change in draft due to water and fuel usage. Motion of the fathometer is not measured. Horizontal accuracy of the fathometer is assumed to be within +/- 3 meters.
Ship motion was recorded with a TSS DMS 2-05 Attitude Sensor, mounted on a head above the interferometric Submetrix 2000 Series transducers. Navigation was recorded using Real Time Kinematic Differential Global Positioning System (RTK-DGPS). The interferometric sonar is an angle-measuring system; depth accuracy decreases with increasing horizontal range. The combined angular accuracy of the Submetrix 2000 Series and the TSS DMS 2-05 attitude sensor is documented as 0.1 degrees. Assuming a constant angular accuracy, and using the International Hydrographic Standard (IHO) of a required 0.3 meter accuracy in < 30 meter water depth, all data collected within the survey fall within the IHO accuracy standards. However, vertical accuracy is also directly affected by the accuracy of both the navigation system and tidal measurements. RTK DGPS vertical accuracy is assumed to be 0.2 meters. Tidal elevations were derived from RTK -DGPS heights sent from a survey-specific base station located on St. George Island.
The base station occupied a temporary monument. The x & y positions were calculated for that location using a 3 day average of 12 hour data sets using the Online Positioning User Service (OPUS, National Geodetic Survey) solution. Tidal elevations were calculated from NOAA Tidal Station #8728690 using the same OPUS solution and then applied to the corrected elevations for the base station at St. George Island. Antenna heights were referenced to Mean Lower Low Water (MLLW) for easier comparison of NOAA nautical charts
Soundings were gridded in OMG SwathEd software using the entire swath width across track to achieve maximum coverage at the scale of the entire Apalachicola Bay/St. George Sound survey area. Although the soundings were manually edited, small data spikes may exist at outer edges of swath.
Pockmark features that appear in the dredge channel of the intracoastal waterway fairways are artifacts of the of the processing methods used to generate a continuous surface from swath bathymetry collected on lines spaced 100m apart.
These data have not been quantitatively compared to previous hydrographic data, although they generally agree with qualitative comparison of published NOAA charts.
Are there legal restrictions on access or use of the data?
- Access_Constraints: None
- Data are not intended for navigational use.
These data should not be used at resolutions for which it is not intended.
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.
508-548-8700 x2348 (voice)
Although this data set has been used by the U.S. Geological Survey (USGS), no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials.
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
|Data format:||Hillshade grid representation of swath bathymetric data collected in the Apalachicola Bay and St. George Sound Florida in format ESRI Grid (version ArcGIS 9.2) ESRI Grid File Size: 0.454|
|Media you can order:||
These data are available as an 8-bit continuous unsigned integer raster in Environmental Systems Research Institute (ESRI) format. To utilize these data, the user must have an image viewer, image processing or ESRI software capable of importing and ESRI ArcRaster grid.
508-548-8700 x2348 (voice)