# Measuring relative time shifts, phase and amplitude differences in time-lapse data.

# The data are supposed to be sorted so that the data from different vintages are present
# in the same ensemble. Different vintages are marked with header year=1999, 2001. etc.,
# and different components (in 3-C data) are differentiated by trace header 'comp'.

# The following measures time shifts, spectral slopes, and phase rotations 
# for all traces with comp=1 relative to the one with year=1999
# The resulting values are placed in headers 'acalib' 'tcalib' and 'phrot' 
# without applying it to the data

*call	wfcalib	param	select	year	1999	comp	1
	
tgate	below_reservoir	range	-30.0	100.0			ok
scale				acalib
tshift		50.0		tcalib
phrot		30.0	3.0	phrot

## note how the measured corrections stored in trace headers can be applied (later):

*call	static	tcalib	remove		# time shift correction

*call	hdrmath
eval	real afact = exp(acalib)	# logarithm of amplitude correction is output by wfcalib,
					# and so it has to be exponentiated to use in 'gain'

*call	gain	remove	afact		# amplitude correction

*call	filter
bslope			phrot		# phase correction