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Open-File Report 03-007

Bathymetry and Acoustic Backscatter of the Mid and Outer Continental Shelf, Head of De Soto Canyon, Northeastern Gulf of Mexico—Data, Images, and GIS

Multibeam Bathymetry and Acoustic Backscatter Data

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This Open-File Report contains the bathymetry and acoustic backscatter data from the 2002 multibeam sonar survey of the Head of De Soto Canyon Region, Northeastern Gulf of Mexico. The data are provided in two formats (XYZ and ESRI GRID) that can be used in a number of GIS and other software packages.


XYZ format

The data are available in comma delimited XYZ (x-coordinate, y-coordinate, value) format.

Instructions

1. Click on the links below to download the files.

2. Uncompress the files. The files are compressed with WinZip 7.0.

3. The uncompression will result in a new comma delimited file (i.e. cenbath.xyz).

Disclaimer: Downloading files from the Internet can sometimes be problematic. Different web browsers and operating systems act differently. The instructions above may vary from system to system or may not work at all.

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XYZ File File Information
Northeast Region
nthbath.zip value = depth: min = -39.8m, max = -107.2m, 8-m spatial resolution, 18Mb compressed, 89Mb uncompressed
nthmos.zip *value = DN: min = 27.0m, max = 224.3m, 8-m spatial resolution, 20Mb compressed, 90Mb uncompressed
 
Central Region
cenbath.zip value = depth: min = -38.6m, max = -146.6m, 8-m spatial resolution, 49Mb compressed, 237Mb uncompressed
cenmos.zip *value = DN: min = 18.0m, max = 235.5m, 8-m spatial resolution, 52Mb compressed, 241Mb uncompressed
 
Southwest Region
sthbath.zip value = depth: min = -35.6m, max = -245.5m, 8-m spatial resolution, 61Mb compressed, 297Mb uncompressed
sthmos.zip *value = DN: min = 19.0m, max = 241.2m, 8-m spatial resolution, 64Mb compressed, 294Mb uncompressed

* NOTE: Acoustic backscatter strength has been converted from decibels (dB) to a non-dimensional digital number (DN) using the conversion,

Absolute Value(2DN/dB)

where DN ranges from 0 to 255 and dB ranges from 0 to -127.


Projection Information
Geographic
Units: Decimal Degrees
Zunits: NO [backscatter]; Meters [bathymetry]
Datum: WGS84

FGDC Compliant Metadata for ASCII XYZ formt

ASCII FAQ
ASCII HTML
ASCII TEXT

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ESRI GRID format

The data are also available in ESRI GRID format that can be used directly in ESRI ArcInfo, ArcView, or any other GIS or remote sensing software package that supports ESRI GRID format. In ArcView, the GRID files will only work with the Spatial Analyst Extension.

Disclaimer: Downloading files from the Internet can sometimes be problematic. Different web browsers and operating systems act differently. The instructions below may vary from system to system or may not work at all.

One known problem is sometimes Netscape Navigator automatically changes the .tgz suffix to .tar during the download. If this happens change the .tar suffix back to .tgz after the download. Double click on the file and Winzip should start up.

Instructions

1. Click on each link below to download the files to the desktop.

2. Uncompress and unbundle the files. Since ESRI GRIDs are directories of files, each directory has been bundled into a single file and then compressed for downloading.

Windows - Double click on each file (nthbath.tgz). Winzip 7.0 will uncompress the file resulting in a new bundled file (nthbath.tar). Double click on the new file and Winzip 7.0 will unbundle the file into a new folder (nthbath). The ESRI GRID (nthbathg) is contained within the folder.

UNIX - Uncompress using "gunzip" then unbundle using "tar xf". The bathymetry and acoustic backscatter GRID files (nthbathg, nthmosg) are contained within each respective folder (nthbath, nthmos).

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ESRI GRID File File Information
Northeast Region
nthbath.tgz value = depth: min = -39.8m, max = -107.2m, 8-m spatial resolution, 9Mb compressed, 37Mb uncompressed
nthmos.tgz value = DN: min = 27.0m, max = 224.3m, 8-m spatial resolution, 7Mb compressed, 229Mb uncompressed
 
Central Region
cenbath.tgz value = depth: min = -38.6m, max = -146.6m, 8-m spatial resolution, 25Mb compressed, 124Mb uncompressed
cenmos.tgz value = DN: min = 18.0m, max = 235.5m, 8-m spatial resolution, 23Mb compressed, 123Mb uncompressed
 
Southwest Region
sthbath.tgz value = depth: min = -35.6m, max = -245.5m, 8-m spatial resolution, 29Mb compressed, 90Mb uncompressed
sthmos.tgz value = DN: min = 19.0m, max = 241.2m, 8-m spatial resolution, 27Mb compressed, 87Mb uncompressed

* NOTE: Acoustic backscatter strength has been converted from decibels (dB) to a non-dimensional digital number (DN) using the conversion,

Absolute Value(2DN/dB)

where DN ranges from 0 to 255 and dB ranges from 0 to -127.


Projection Information
Projection: UTM
Zone: 16
Datum: WGS84
Units: Meters
Zunits: NO [backscatter]; Meters [bathymetry]

FGDC Compliant Metadata for ArcInfo GRID format:

GRID FAQ
GRID HTML
GRID TEXT

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Page Last Modified: Tuesday, April 01, 2014, 01:27:04 PM