Handle multiple sources and receivers with varying orientations in 'bipole'

[AndyMcAliley]

In empymod.bipole, when src or rec is formatted as [x0, x1, y0, y1, z0, z1] with multiple bipoles with different azimuths, the fields are computed as if all bipoles have the same orientation as the first in the list. For example, for two orthogonal sources:

import numpy as np
from empymod import bipole

xx = np.linspace(-100,100,40)
yy = np.linspace(-100,100,40)
X,Y = np.meshgrid(xx,yy)
xs = X.flatten()
ys = Y.flatten()

epm_args = {
    'src':[[0,20],[20,20],[0,0],[0,20],1e-2,1e-2],
    'rec':[xs,xs+10,ys,ys,1e-3,1e-3],
    'depth':[0],
    'res':[1e20,1],
    'freqtime':1,
    'srcpts':15,
    'verb':0,
    'epermH':[0,1],
    'epermV':[0,1]
}

bex = bipole(**epm_args)
np.unique(bex[:,1])

All entries of bex[:,1] are 0+0j. Similarly, for two orthogonal receivers,

epm_args = {
    'src':[0,20,0,0,1e-2,1e-2],
    'rec':[[30,30],[35,30],[30,30],[30,35],1e-3,1e-3],
    'depth':[0],
    'res':[1e20,1],
    'freqtime':1,
    'srcpts':15,
    'verb':0,
    'epermH':[0,1],
    'epermV':[0,1]
}
bex = bipole(**epm_args)
bex[1]

Output: 0j.

[prisae]

Thanks for reporting @AndyMcAliley , this seems to be a bug. I'll look into it!

[AndyMcAliley]

I think utils.get_abs() is the culprit:

 # Remove if source is x- or y-directed
    check = np.atleast_1d(srcazm)[0]
    if np.allclose(srcazm % (np.pi/2), 0):  # if all angles are multiples of 90
        if np.isclose(check // (np.pi/2) % 2, 0):  # Multiples of pi (180)
            bab[:, 1] *= False        # x-directed source, remove y
        else:                                      # Multiples of pi/2 (90)
            bab[:, 0] *= False        # y-directed source, remove x

[prisae]

Yes, you are right. You touched a scenario that I never used so far...! I fixed it and will soon push an update.

[prisae]

And it obviously got not caught by the tests, so I'll have to add a test too...

[prisae]

OK, a fix is in the branch azimuth-dip. Could you test it (pip install git+https://github.com/empymod/empymod@azimuth-dip)?

If it works I will push later this week a new release.

[AndyMcAliley]

Looks good to me, for both sources and receivers! Thanks so much!