debugging info

Author: JanThorbecke

extrap/doc/OpenExtrap.pdf

@@ -25,7 +25,7 @@
 % Make a version of the title for latex and html
 \newdimen{\mybaselineskip}
 \mybaselineskip=24pt
-\title{OpenExtrap 1.0}
+\title{OpenExtrap 1.1}
 
 \author{Jan W. Thorbecke}
 

extrap/doc/OpenExtrap.tex

@@ -97,7 +97,9 @@ \subsection{Parameters}
 
 \subsection{General parameter description}
 
-The shots to be migrated ({\tt file\_shot}) and the gridded subsurface files ({\tt file\_vel} and {\tt file\_vels}) should have the same lateral extend being defined by the {\tt gx} headers.  The position of the receivers of the data in the subsurface grid is done by means of the {\tt gx} header value of the velocity model corresponding to the {\tt gx} header value in the data to be extrapolated. The distance between the traces in the velocity model should be smaller or equal to the distance between the receivers/shots. The program assigns the {\tt gx} value of the receivers to the nearest grid point in the velocity model. The number of depth steps is controlled with the parameter {\tt ndepth=}. To avoid reflections at the edges of the model the parameter {\tt ntap} can be set. {\tt ntap} indicates the number of points at the edges for which a spatial taper is designed according to: $\exp{(-(0.4*(ntap-ix)/ntap)^2)}$. Choosing {\tt ntap} equal to half of the operator length is an optimimum value. 
+The shots to be migrated ({\tt file\_shot}) and the gridded subsurface files ({\tt file\_vel} and {\tt file\_vels}) should have the same lateral extend being defined by the {\tt gx} headers.  The position of the receivers of the data in the subsurface grid is done by means of the {\tt gx} header value of the velocity model corresponding to the {\tt gx} header value in the data to be extrapolated. The distance between the traces in the velocity model should be smaller or equal to the distance between the receivers/shots. The program assigns the {\tt gx} value of the receivers to the nearest grid point in the velocity model. The number of depth steps is controlled with the parameter {\tt ndepth=}. To avoid reflections at the edges of the model the parameter {\tt ntap} can be set. {\tt ntap} indicates the number of points at the edges for which a spatial taper is designed according to: $\exp{(-(0.4*(ntap-ix)/ntap)^2)}$. Choosing {\tt ntap} equal to half of the operator length is an optimum value. 
+ 
+The {\tt sx} or {\tt fldr} headers in {\tt file\_shot} determine a single shor record. As long as {\tt sx} or {\tt fldr} header value remain constant the program considers these traces belonging to a single shot. If one of these values changes this trace is then considered to belong to the next shot. Be careful for example with common-offset data. In this kind of data set the {\tt sx} or {\tt fldr} header value usually change with each trace, hence each trace is considered to be one shot by the program. To overcome this problem set {\bf both} {\tt sx} or {\tt fldr} header values to a constant value 
 
 Topography is taken into account by using a velocity model which has zero velocities above the defined topography. In that case the position of the source and receivers is lowered into the velocity model until a non-zero velocity is found. From that depth the extrapolation of that point is started.