The Pick Window shows you the text of only the picks on the current plane, or record.

• Try pressing the Auto-Pick button. This will erase any picks present that have not been saved, and attempt to make a first-arrival pick of each trace.

• The picks on the record currently shown in the data plot will appear after a while in the pick window. In the data display window, move the Plane Index slider back and forth to observe the quality of the automatic picks on all your records. You will observe the pick text changing as it flips from the picks of one plane to those of the next. If you have exceptionally clean survey data, you may be satisfied with the automatic picks.

  Our ``dixie-refr.sgy'' data will auto-pick more than 90% correctly. Blank traces (that you can see have low amplitude before tegain) are not auto-picked, which is good. Some traces at very small offsets do not auto-pick well, since the pick time is too close to zero time. Some traces at farther offsets, where the first arrival is weak, auto-pick too late.

• The picks are written out in the Pick window and marked on the data display. You can select pick text, copy it to the clipboard (with Control-C or Command-C), and paste it into another application such as Wordpad or Excel. You can also delete picks by removing lines, or add text annotations. Text in the window that does not represent a pick will be ignored. If you have added or deleted picks and want to see the resulting marks on the data display, refresh the display with the Refresh button at the bottom of the pick window. The format of the pick text is, left to right: Amplitude; Time Sample Index; Time, seconds; Trace Index; Trace Label; Plane Index; Plane Label; Field Record Number; Source Point Number; Receiver Point Number; Source X Coord., meters; Source Y Coord., meters; Source Elevation, meters; Receiver X Coord., meters; Receiver Y Coord., meters; Receiver Elevation, meters; Offset, meters; and an allset field used by other routines. Your 492-refraction.zip archive contains a ``dixie-refr.xls'' Excel spreadsheet demonstrating what the picks of the first and fifth records should look like on your time-distance plot.

• In order to get the picks from all planes or records, you need to press the Show All button on the pick window. If you have a lot of planes, there may be too much pick text and it will not copy to the clipboard. In this case, press the Save button on the pick window, and all of the pick text will get saved into a file. When you save a JRG Pack, the folder will contain a file with all the picks, ending in ``.pck''. You can import pick files into spreadsheets such as Excel.

• The automatic picks are based on where each trace exceeds a threshold amplitude factor relative to a small initial part of the trace. You can repeat your use of the Auto-Pick button as many times as you want to test different picking parameters, although you will lose all previous picks each time. You can adjust the threshold factor from the Auto-Pick Threshold sub-menu of the Edit menu on the Pick window, and the size of the initial trace sample from the Threshold Above sub-menu of the Edit menu.

• Once you are satisfied that the automatic picker has done the best job it can, you can go on to correct the picks.

• The text for the new pick will appear at the end of the list in the Pick window, in the order you hand-pick; you may have to scroll down to see it. If you picked the wrong place, you can select Undo Last Pick from the Edit menu of the data window or the Pick window, or press Control-U (or Command-U on a Mac).

• Only the traces you either auto-pick or hand-pick will get picks; Viewmat does no interpolation or phase correlation between picks.

• Re-picking a trace will not cause previous picks of that trace to disappear - you would have to delete those from the Pick window by hand. Deleting superseded picks is not necessary, because only the last-made pick on any trace will be exported to SeisOpt. All picks in the pick window will still appear if you save the pick text, however, or save a plot of the record display. You can just ignore these picks when you interpret the results.

• Use the Plane Index slider on the data display to cycle through and pick traces on each record.

• You do not have to pick every trace. You do have to re-pick each trace that was incorrectly picked by Auto-Pick. While missing picks may decrease resolution and depth penetration in your SeisOpt results, globally optimized discovery will still produce the best result possible from even sparsely and irregularly sampled pick data.

• During a long session of hand-picking, periodically run Save JRG Pack... from the File menu on the data window. If your computer locks up, then you can easily reload the file using Load JRG Pack..., including all your picks, and resume where you left off.

• Click the Save button in the Pick Window when you are done re-picking, or just Save JRG Pack. This saves the pick data for all planes into one file. The saved pick file is plain text, so you can import it into your favorite spreadsheet (or paste it in and then use Edit->Text to Columns) to make a time-distance plot of the picks from the two end records. Your 492-refraction.zip archive contains a ``dixie-refr.xls'' Excel spreadsheet demonstrating what the picks of the first and fifth records should look like on your time-distance plot.
  • For instance, when you import the pick text into Excel, under Delimiters you can check Space and Other, and enter the equals sign ``='' as a delimiter.
  • After importing the picks into a spreadsheet, make an X-Y scatter plot using column U (after "gx" in Excel) ``Receiver X Coord., meters'' as the X-axis and column C ``Time, seconds'' as the Y-axis.
  • Just plot the picks from the first and last records by deleting all but the first 48 and last 48 rows in the spreadsheet. Check the ``rec'' numbers to be sure. You may want to choose Sort... from the Data menu in Excel and sort by ``svp'' (column K) and secondarily by ``gvp'' (column M). Then you should have an easy time deleting the rows from the middle shots. If you remember that the erroneous automatic picks were too late, you can also look at column C to remove the rows from the superceded automatic picks, that you re-did by hand.
  • Plotting is easiest in Excel if you select column C, copy it, and then select column V and paste it in. Now select columns U and V, containing the receiver X coordinate and the pick time, respectively.
  • Go to the ChartWizard and select an XY Scatter plot with grid lines. Make sure to properly label the axes. Always use only approved SI units and their abbreviations.
  • When you are looking at the plot, you can double-click on the time axis to set it to a more useful scale, by unchecking automatic and using a maximum of 0.4 s. You can also set finer grid-line intervals, for easier calculation of slopes you draw on the printout of the plot by hand. You can plot the time axis increasing up or down as suits you.
  • Make a printout of this plot (just print the page the plot is on). Make several copies of this plot for you to draw on.

• If you want to save a plot of more than one record, you have to move the Plane Index slider to show another record, and then select Write PostScript File again. Viewmat will suggest a file name that includes the unique index of that plane.

• This file is Generic PostScript code (not EPS) and can't be imported to older word-processing programs. Later versions of applications such as Word, Powerpoint, Corel, Canvas, and Illustrator will import the PostScript.

• To view or print a PostScript file, you can drop a PostScript file onto Adobe Acrobat full version (not the free Acrobat Reader), which is on the desktop of every UNR lab computer.

• If you can't access Acrobat full version, you can obtain the free Ghostview application from the Univ. of Wisconsin at www.cs.wisc.edu/~ghost/, which will display and print the PostScript on your PC and non-PS printer.

• You can save a color plot as a PostScript file, and then edit the PostScript code to print an effective plot in black and white:
  1. Open the PostScript file in Wordpad or SimpleText.
  2. Search for the text ``/colorplot true def'', not far from the top of the file.
  3. Change that text to ``/colorplot false def''. It will now effectively use the Seismic Variable Density gray scale.
  4. Save the file.
  5. Now drop it into Acrobat or Word to print it to a black-and-white printer.
  6. The color information is preserved; you can always re-edit the PostScript file before sending it to a color printer.
  This procedure is better than trying to change the colors in a markup program.