ASP_UTIG
The following is meant to help explain how we think you will want to navigate the data center portal. If your questions are not answered here, please contact one of us.
We expect users to have high-speed network connections to display the images, results of searches and to download binary data. The search capability and small images are freely available but check our terms and conditions for appropriate usage in the Registration link.
We suggest you start by registering at the Registration link where we explain the purpose of registering and how we use the information. Free access is granted within seconds. Through your account you can request access to restricted data and large images.
To start searching/browsing, use the Function:Search Map option or the Function: Cruise Info option.
The following questions are answered below. They will be updated as the web site becomes better defined.
A. How to find a seismic line
L-2. My software is having problems reading the navigation in the SEG-Y headers. L-3. My software is having problems plotting the data at the correct depth (number of seconds).
B. How to obtain more information on the line processing
C. How to efficiently use the Search Cruise Index page
D. Saving a file to disk
E. Saving an image to disk (Such as a seismic line gif)
F. Plotting a navigation file using GMT
G. Converting a PostScript file to GIF format
H. Accessing a PDF file
I. Expanding compressed files
J. How to get a copy of a thesis
K. My seismic plot looks wrong - the ocean floor is off.
L-1. My software is having problems reading the SEG-Y file.
Links
Society of Exploration Geophysicists (SEG) Technical Standards
SEG-Y (revision 0) standard - page 9 has byte format
SEG-Y (revision 1) standard
SIOSEIS' USE OF THE SEG-Y TRACE HEADER
A. How to find a seismic line
The web introduction page offers several paths to locate lines of
interest. For the first time user, it is best to start with the map based
method.
Map method
1. Click the Function:Search by map.
5. Click on the line name and it will download the segy file.
Click on small image for larger image.
7. It may be necessary to download the navigation files to locate
a specific line of interest. To get to the navigation file use the Function:
Cruise Info or Function: Search
Metadata. If you know the line name or cruise name then using the Search
metadata is efficient.
B. How to obtain more information on the line processing
Additional processing information may be available for some
cruises and/or lines. If shipboard data reduction information is available, it
will be noted on the Function:Search by cruise results.
C. How to efficiently use the Search Metadata function
The Function:Search by cruise is a great place to start if you know
the name of the cruise, the line name or have a keyword on which to search. It gives
access to lots of information organized by cruise.
1. Multiple words entered in the "Keywords" field are searched for using a Boolean. That is, if you entered "Caribbean Basin"; the search would return data linked to both "Caribbean" and to "Basin" - so you might see data from the Newfoundland Basin, the Nauru Basin, the Caribbean, etc. (We plan to replace this logic.)
2. If you only want processed data, not the shot data, be sure to enter "shot" (without the quotes) in the "Exclude Keywords" field. This is now the default.
D. Saving a file to disk Modified from NCSA Mosaic for MS Windows User Guide: Tips and Tricks:
Current File
To save the current file (i.e., the file displayed in your
Document View window) to disk:
1. Select Save As from the File menu
2. With the right mouse button click on Save to Disk. Select the
file format you want (HTML or text).
To save a hyperlinked document to disk without opening it:
1. Place your cursor on the hyperlink
2. Using Explorer, right-clicking the link gives the option to
"Save Target As" Using Netscape, hold down the shift key and then
left-click the link.
3. Click on 'Save to Disk' in the dialog box. Select the file
format you want (HTML or text).
4. Locate the appropriate directory and enter a filename. Click
OK.
E. Saving an image to disk (Such as a seismic line gif)
1. Place cursor over the image.
2. Click the right mouse button. A dialog menu should appear.
3. Explorer: Click 'Save Picture As' and save it to your disk.
OR Netscape: Click 'Save Image As' and save it to your disk.
F. Plotting a navigation file using GMT
# GMT command file to produce a map showing navigation
psbasemap -V -P -K -JM7.75 -R-10/30/-30/0 -Bf2a4/f2a4NWse > ps
pscoast -V -O -K -JM -R -W2 -N1 -Df >> ps
psxy -V -O -JM -R -M -W2/000/255/000p -Sp.05 FM0102.all.nav -: -H2 >>ps
G. Converting a PostScript file to GIF format
From http://web.cs.ualberta.ca/~goebel/conversions/translate/pstogif:
#! /bin/sh
# http://www.unizh.ch/ps/wmgraphe.html
# pstogif
#
# ***** Use to convert a single image from powerpoint ps to gif *****
# Call it by putting the .ps file name as first argument but without the ".ps" extension
# Ex: for "Intro_Tbl.ps"
use "pstogif Intro_Tbl"
gs -r72x72 -sDEVICE=ppmraw -sOutputFile=$1.ppm $1.ps
pnmcrop < $1.ppm | ppmtogif > $1.gif
H. Accessing a PDF file
Files stored in PDF format may be displayed/printed using Adobe
Acrobat Reader, available as freeware at
http://get.adobe.com/reader/.
I. Expanding compressed files
We use tar (file extension ".tar") and gzip (file
extension ".gz") to group and compress files. To uncompress and
expand these under Solaris OS:
gunzip file.tar.gz
tar -xvf file.tar
Aladdin Systems offers StuffIt Expander for Windows, Macintosh, Linux, and Solaris, with free downloads at http://www.stuffit.com/expander/index.html.
J. How to get a copy of a thesis
Some suggestions for getting copies of theses include contacting the individual or the school that the individual attended. Also, ProQuest has a number of theses available on-line: http://www.proquest.com/en-US/products/dissertations/.
K. My seismic plot looks wrong - the ocean floor is off.
Sometimes SEG-Y data have a deep-water delay in the headers. Plotting software should be able to take this into account. The delay (in milliseconds) is stored in bytes 109-110 (see SIOSEIS).
L. My software is having problems reading the SEG-Y file.
There are several data formats (e.g., IBM floating point, 32bit integer, 32bit IEEE floating point, etc.) for the SEG-Y data. The SEG-Y format type can be found in the SEG-Y Binary Tape Header, byte 13 (see http://sioseis.ucsd.edu/segy.header.html):
=1, ibm floating point.
=2, 32 bit integer.
=3, 16 bit integer.
=4, 16 bit UTIG floating point.
=5, 32 bit IEEE floating point.
Newer software often assumes that the number of samples is the same for all traces. This may not be true, especially for older data. Have your software check bytes 115-116 in the trace headers to determine the number of samples in a trace.
L-2. My software is having problems reading the navigation in the SEG-Y headers.
The SEG-Y header format we use is described at http://sioseis.ucsd.edu/segy.header.html. Longitude is stored as seconds of arc in bytes 73-76. Latitude is stored as seconds of arc in bytes 77-80. Bytes 89-90 indicate the coordinate unit is arc seconds. In bites 71-72 is the scalar to be applied to the coordinates. So, the lat/long in the segy header are in 1/1000 of seconds of arc. Divide the 32-bit integer number in the header by 3600000 and you'll have a decimal degree number.
L-3. My software is having problems plotting the data at the correct depth (number of seconds).
Check that your software is identifying any deep water delay (set in the trace header bytes 181-184, in milliseconds).