Topic:
How to clip anomalously large amplitude values while loading.

Description:

Solution:
Application > DataManager > Seismic > Load Seismic:
 - Click 'Define input format ...'  
 - Toggle under 'Key parameter source' SP or CDP to 'Expression' (which ever one
   you want to use) 
 - Select 'Shot point/CDP expression...'
 - Type in one of the expressions below in area designated by --> for example,
   --> CDP = cdp. Then on next line below, type in expression.

In expressions, EDITVAL works the following way:

EDITVAL has the following parameters:
EDITVAL (clipa[,clipb[repla[,replb[num[,notify]]]]])

where clipa: clip value (If only 1 argument, then this is the +/- clipval)
EDITVAL (1000000) will replace any value outside of (-1000000;+1000000) with 0.

clipb: clip value (Unclipped range is clipa:clipb)
EDITVAL (-99, 99) will replace any value outside of (-99:+99) with 0.

repla: value to replace clipped values. Default is 0,0 if nor replb, then this
is the +/- replaceval.

replb: value to replace clipped values, clipa replace with repla, clipb is
replace with replb.
EDITVAL (-77, 77, 75) will replace a value less that -77 with 75 and replace
any value greater than +77 with +75.
EDITVAL (-60, 60, 0, 60) will replace any value less than -60 with 0.0 and
replace any value greater than 60 with 60.

num: maximum number of values to clip (default is all).
EDITVAL (-60, 60, 0, 60, 2) same as above but will only replace the first two
values that are out of range.

notify: 0=no, else generate listing line of clip counts (default is 0m no
listing line).
EDITVAL (-60, 60, 0, 60, 2,1) same as above, but generate line listing for any
trace that was clipped, giving the count of the number of clips.

Use the variable number of clips parameter:
EDITVAL (-60, 60, 0, 60, A1*1000, 1) setup up to clip, but if A1 is zero then no
clipping is done. This can be used to turn clipping on/off based on some
variable.

=======================
Example:

In the 'Define 2D input data format' menu, set the CDP header location to the
'expression'.  

Then, clicked on the blue button - 'Shot point/CDP expression'. 
 
In the 'define 2D shot point and CDP expressions' menu, at the bottom, after
'CDP', put 'cdp' (not in quotes).  

Then, on the NEXT line, put 'editval(-100,100,0,0,10000,1)' ....again, not in
quotes.  

Then, click on the 'OK' button at the bottom of that menu, which will bring you
back to the 'Define 2D input data format' menu.  

In this menu, set the CDP header location back to 'Trace header' toggle.  

Then, press the 'Apply' button at the bottom, and then make sure you save the
loading definition.

This way, you clip any samples outside the range of -100 and 100 to 0, up to
10,000 samples, and output information on what was clipped to the log file.
 





Last Modified on: 04-DEC-98