GRM - Generalized Reciprocal refraction analysis for a single layer	     grm <stdin >stdout  [parameters]    		 		 Required parameters:							 nt=		Number of arrival time pairs				 dx=		Geophone spacing (m)					 v0=		Velocity in weathering layer (m/s)			 abtime=	If set to 0, use last time as a-b, else give time (ms)   Optional parameters:							 XY=      Value of XY if you want to override the optimum XY			  algorithm in the program. If it is not an integer multiple of 	 dx, then it will be converted to the closest					 one.								XYmax   Maximum offset distance allowed when searching for      		optimum XY (m)  (Default is 2*dx*10)				depthres  Size of increment in x during verical depth search(m) 		  (Default is 0.5m)					 Input file:									4 column ASCII - x,y, forward time, reverse time 		 Output file:									1) XYoptimum  								2) apparent refractor velcocity						3) x, y, z(x,y), y-z(x,y)							z(x,y) = calculated (GRM) depth below (x y) 				y-z(x,y) = GRM depth subtracted from y - absolute depth       .............							      4) x, y, d(x,y), y-d(x,y), (error)  						d(x,y) = dip corrected depth estimate below (x,y)       		y-d(x,y) = dip corrected absolute depth 				error = estimated error in depth due only to the inexact		      matching of tangents to arcs in dip estimate.	      If the XY calculation is bypassed and XY specified, the values	      used will precede 1) above.  XYoptimum will still be calculated	      and displayed for reference.					 Notes:							       	      Uses average refactor velocity along interface.			  Credits:							            CWP: Steven D. Sheaffer						 								            D. Palmer, "The Generalized Reciprocal Method of Seismic	       Refraction Interpretation", SEG, 1982.