Online Links:
Online Links:
This data release makes multibeam echosounder data from the 1998 survey of the sea floor offshore of Fire Island Inlet, New York, available in digital form. The GeoTIFF image of shaded-relief bathymetry provides a visualization of the bathymetry that accentuates small features that cannot be effectively shown as contours alone. The shaded-relief image was created by vertically exaggerating the bathymetry 4 times and then artificially illuminating the relief by a light source positioned 45 degrees above the horizon from an azimuth of 60 degrees. The illumination from 60 degrees, approximately parallel to the survey lines, minimizes artifacts caused by small depth changes that may occur between lines.
1. Create a 3-m grid of the bathymetric soundings for the Fire Island site using the SwathEd routine weigh_grid.
Command line: weigh_grid -fresh_start -omg -tide -coeffs -mindep -2 -maxdep -800 -beam_mask -beam_weight -custom_weight EM1000_Weights -butter -power 2 -cutoff 6 -lambda 1.5 gridFile filename.merged
2. Create a shaded-relief image of the bathymetry using SwathEd routine addSUN (sun elevation of 45 degrees from 60, vertically exaggerating 4 times). The shaded relief file created from the grid is mapped into the same projection as the grid and carries over the projection information (custom Mercator projection, central meridian -75 degrees, latitude of true scale 40 degrees north) used to create the grid.
Command line: addSUN -elev 45 -azi 60 -vert_exag 4.0 gridFile.r4 filename.shade
3. Use a two-point linear contrast stretch (0-254; 255 is no data) to enhance the shaded-relief image:
Command line: stretchacres -low 150 -high 200 -in filename.shade -out filename_shade.stretch Person who carried out this activity:
Command line: rawtopgm -headerskip 1024 image_width image_height filename_shade.stretch | pnmtoTIFF -none - > filename.tif Person who carried out this activity:
Command line: jview filename_shade.stretch Person who carried out this activity:
Online Links:
Are there legal restrictions on access or use of the data?Access_Constraints: None
Use_Constraints: These data are not to be used for navigation purposes.
Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. 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: | GeoTIFF image of shaded-relief bathymetry and associated metadata from a multibeam survey offshore of Fire Island Inlet, New York, compressed in a WinZip (version 14) file in format GeoTIFF (version ArcGIS 9.3) GeoTIFF image Size: 1.5 |
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Network links: |
https://www.sciencebase.gov/catalog/file/get/56ba3362e4b08d617f649000?name=fire_srelief3m.zip https://doi.org/10.5066/F7Z899GG |
The GeoTIFF image of shaded-relief bathymetry is compressed into a WinZip (version 14) file (fire_srelief3m.zip). To use these data, the user must have software capable of uncompressing the zip file and ArcGIS or another GIS application package capable of viewing the data.