def test_amplitude(self):
"""
Tests the basic algorithm returns the right amplitude
location.
"""
amplitude = energy(self.data, self.n_samples)
max_amp = amax(amplitude)
ms_sin = 0.5 # The MS energy of a sin wave
self.assertAlmostEquals(ms_sin, max_amp, places=3)
# Check that it is in the right location
self.assertAlmostEqual(max_amp, amplitude[501], places=3)
def test_amplitude(self):
"""
Tests the basic algorithm returns the right amplitude
location.
"""
amplitude = energy(self.data, self.n_samples)
max_amp = amax(amplitude)
ms_sin = 0.5 # The MS energy of a sin wave
self.assertAlmostEquals(ms_sin, max_amp, places=3)
# Check that it is in the right location
self.assertAlmostEqual(max_amp, amplitude[501], places=3)
def dipsteer(data,
window_length,
stepout,
maxlag,
overlap=1,
dt=1,
return_correlation=False):
"""
Calculates a dip field by finding the maximum correlation between
adjacent traces.
:param data (ndarray): A 2D seismic section (samples,traces) used to
calculate dip.
:param window_length (float): The length [in ms] of the window to use.
:param stepout (int): The number of traces on either side of each point
to average when calculating the dip.
:param maxlag (float): The maximum amount time lag to use when correlating
the traces.
:keyword overlap (float): The fractional overlap for each window. A value
of 0 uses no redudant data, a value of 1 slides the dip correlator one
sample at a time. Defaults to 1.
:keyword dt (float): The time sample interval in ms.
:keyword return_correlation (bool): Whether to return the correlation
coefficients. If you choose True, you'll get a tuple, not an ndarray.
:returns: a dip field [samples/trace] of the same shape as the input data
(and optionally correlation coefficients, in which case you'll get a
tuple of ndarrays back).
"""
maxlag = int(maxlag)
dip = np.zeros(data.shape)
crcf = np.zeros(data.shape)
window_length = int(np.floor(window_length / dt))
# Force the window length to be odd for index tracking.
if not (window_length % 2):
window_length += 1
# Define time windows.
if overlap == 1:
stride = 1
else:
stride = int(window_length * (1 - overlap))
n_windows = np.ceil((data.shape[0] - window_length) / stride) + 1
# Normalize each trace to the same RMS energy.
norm_factor = np.sqrt(np.abs(energy(data, window_length)))
norm_data = data / (norm_factor + 1e-9) # To avoid div0 error.
# Replace the 0/0 with 0.
norm_data = np.nan_to_num(norm_data)
# Mid point in the data which corresponds to zero dip.
zero_dip = (np.floor(window_length / 2.0) + maxlag)
s = stepout + 1
# Loop over each trace we can do a full calculation for.
for i in np.arange(s, data.shape[-1] - s):
i = int(i)
# Loop over each time window.
for j in np.arange(0, n_windows):
start = int((j * stride) + (maxlag))
end = start + window_length
# Don't compute last samples if we don't have a full window.
if (end > (norm_data.shape[0]-maxlag)):
break
kernel = norm_data[start: end, i]
dips_j, crcf_j = 0, 0
# Correlate with adjacent traces.
for k in np.arange(1, s):
k = int(k)
# Do the trace on the right.
r_trace = norm_data[start - (k*maxlag): end + (k*maxlag), i+k]
cor_r = np.correlate(kernel, r_trace, mode='same')
if (np.amax(cor_r) < .1):
dip_r = 0
else:
dip_r = (np.argmax(cor_r) - zero_dip) / k
# Do the left trace.
l_trace = norm_data[start - (k*maxlag): end + (k*maxlag), i-k]
cor_l = np.correlate(kernel, l_trace, mode='same')
if (np.amax(cor_l) < .1):
dip_l = 0
else:
dip_l = -(np.argmax(cor_l) - zero_dip) / k
dips_j += dip_r + dip_l
crcf_j += np.argmin(cor_l) + np.argmin(cor_r)
# Average the result
dips_j /= (2. * stepout)
crcf_j /= (2. * stepout)
# Update the output
dip[start: start+stride, i] = dips_j
crcf[start: start+stride, i] = crcf_j
if return_correlation:
DipSteer = namedtuple('DipSteer', ['dip', 'correlation_coeff'])
return DipSteer(dip, crcf)
else:
return dip
def dipsteer( data, window_length, stepout,
maxlag, overlap=0., dt=1 ):
"""
Calculates a dip field by finding the maximum correlation between
adjacent traces.
:param data: A 2D seismic section (samples,traces) used to
calculate dip.
:param window_length: The length [seconds] of the window to use
:param dt: The time sample interval of the traces.
:param stepout: The number of traces on either side of each point
to average when calculating the dip.
:param maxlag: The maximum amount time lag to use when correlating
the traces.
:keyword overlap: The fractional overlap for each window.
A value of 0 uses no redudant data, a value of 1
slides the dip correlator one sample at a time.
Defaults to 0.5
:returns: a dip field [samples/trace] of the same shape as the
input data, and correlation coefficients corresponding
to the data.
"""
dip = np.zeros( data.shape )
window_length = np.floor( window_length / dt )
# Force the window length to be odd for index tracking
if not ( window_length % 2 ): window_length+=1
# Define time windows
stride = window_length * ( 1 - overlap )
n_windows = np.ceil( ( data.shape[0] - window_length ) /
stride ) + 1
# Normalize each trace to the same RMS energy
norm_factor = np.sqrt( energy( data, window_length ) )
norm_data = data / norm_factor
# Replace the 0/0 with 0
norm_data = np.nan_to_num( norm_data )
# Mid point in the data which corresponds to zero dip
zero_dip = ( np.floor( window_length / 2.0) + maxlag )
# Loop over each trace we can do a full calculation for
for i in np.arange( stepout +1, data.shape[-1] - (stepout +1) ):
# Loop over each time window
for j in np.arange( 0, n_windows):
start = (j * stride) + ( maxlag )
end = start + window_length
# Do not compute last samples if we don't
# have a full window
if ( end > (norm_data.shape[0]-maxlag) ): break
# Get the kernel
kernel = norm_data[ start : end, i ]
dips_j = 0
# Correlate with adjacent traces
for k in np.arange( 1, stepout + 1 ):
# Do the trace on the right
r_trace = norm_data[ start - (k*maxlag) : \
end + (k*maxlag), i+k ]
cor_r = np.correlate( kernel, r_trace, mode='same' )
if ( np.amax( cor_r ) < .1 ): dip_r = 0
else:
dip_r = ( np.argmax( cor_r ) - zero_dip ) / k
# Do the left trace
l_trace = norm_data[ start - (k*maxlag) : \
end + (k*maxlag), i-k ]
cor_l = np.correlate( kernel, l_trace, mode = 'same' )
if ( np.amax( cor_l ) < .1 ): dip_l = 0
else:
dip_l = -( np.argmax( cor_l ) - zero_dip ) / k
dips_j += dip_r
dips_j += dip_l
# Average the result
dips_j /= ( 2. * stepout )
# Update the output
dip[ start : start + stride, i ] = dips_j
return dip
def dipsteer(data, window_length, stepout, maxlag, overlap=0., dt=1):
"""
Calculates a dip field by finding the maximum correlation between
adjacent traces.
:param data: A 2D seismic section (samples,traces) used to
calculate dip.
:param window_length: The length [seconds] of the window to use
:param dt: The time sample interval of the traces.
:param stepout: The number of traces on either side of each point
to average when calculating the dip.
:param maxlag: The maximum amount time lag to use when correlating
the traces.
:keyword overlap: The fractional overlap for each window.
A value of 0 uses no redudant data, a value of 1
slides the dip correlator one sample at a time.
Defaults to 0.5
:returns: a dip field [samples/trace] of the same shape as the
input data, and correlation coefficients corresponding
to the data.
"""
dip = np.zeros(data.shape)
window_length = np.floor(window_length / dt)
# Force the window length to be odd for index tracking
if not (window_length % 2): window_length += 1
# Define time windows
stride = window_length * (1 - overlap)
n_windows = np.ceil((data.shape[0] - window_length) / stride) + 1
# Normalize each trace to the same RMS energy
norm_factor = np.sqrt(energy(data, window_length))
norm_data = data / norm_factor
# Replace the 0/0 with 0
norm_data = np.nan_to_num(norm_data)
# Mid point in the data which corresponds to zero dip
zero_dip = (np.floor(window_length / 2.0) + maxlag)
# Loop over each trace we can do a full calculation for
for i in np.arange(stepout + 1, data.shape[-1] - (stepout + 1)):
# Loop over each time window
for j in np.arange(0, n_windows):
start = (j * stride) + (maxlag)
end = start + window_length
# Do not compute last samples if we don't
# have a full window
if (end > (norm_data.shape[0] - maxlag)): break
# Get the kernel
kernel = norm_data[start:end, i]
dips_j = 0
# Correlate with adjacent traces
for k in np.arange(1, stepout + 1):
# Do the trace on the right
r_trace = norm_data[ start - (k*maxlag) : \
end + (k*maxlag), i+k ]
cor_r = np.correlate(kernel, r_trace, mode='same')
if (np.amax(cor_r) < .1): dip_r = 0
else:
dip_r = (np.argmax(cor_r) - zero_dip) / k
# Do the left trace
l_trace = norm_data[ start - (k*maxlag) : \
end + (k*maxlag), i-k ]
cor_l = np.correlate(kernel, l_trace, mode='same')
if (np.amax(cor_l) < .1): dip_l = 0
else:
dip_l = -(np.argmax(cor_l) - zero_dip) / k
dips_j += dip_r
dips_j += dip_l
# Average the result
dips_j /= (2. * stepout)
# Update the output
dip[start:start + stride, i] = dips_j
return dip