Problems with line merging geometries near the anti-meridian

fuzzy.py

from shapely import wkt
from shapely import ops
import matplotlib.pyplot as plt
%matplotlib inline

a = wkt.loads("LINESTRING (-180 68.96363636363637, -177.55 68.2, -174.92825 67.20589, -175.01425 66.58435, -174.33983 66.33556, -174.57182 67.06219, -171.85731 66.91307999999999, -169.89958 65.97723999999999, -170.89107 65.54139000000001, -172.53025 65.43791, -172.555 64.46079, -172.95533 64.25269, -173.89184 64.2826, -174.65392 64.63124999999999, -175.98353 64.92288000000001, -176.20716 65.35666999999999, -177.22266 65.52024, -178.35993 65.39052, -178.90332 65.74044000000001, -178.68611 66.11211, -179.88377 65.87456, -179.43268 65.40411, -180 64.97970870219837)")
b = wkt.loads("LINESTRING (180 64.97432999999999, 178.7072000000003 64.53493, 177.4112800000002 64.60821, 178.3130000000002 64.07593, 178.9082500000002 63.25197000000014, 179.37034 62.98262000000011, 179.48636 62.56894, 179.2282500000001 62.30410000000015, 177.3643 62.5219, 174.5692900000002 61.76915, 173.68013 61.65261, 172.15 60.95, 170.6985000000001 60.33618, 170.3308500000003 59.88177, 168.90046 60.57355, 166.2949800000003 59.78855000000021, 165.8400000000002 60.16, 164.87674 59.7316, 163.5392900000001 59.86871, 163.2171100000002 59.21101, 162.0173300000001 58.24328, 162.05297 57.83912, 163.19191 57.6150300000001, 163.0579400000002 56.15924000000012, 162.1295800000002 56.12219, 161.70146 55.28568000000016, 162.1174900000002 54.85514, 160.3687700000004 54.34433, 160.0217300000002 53.20257, 158.5309400000002 52.95868000000024, 158.23118 51.94269, 156.7897900000003 51.01105, 156.4200000000002 51.7, 155.99182 53.15895, 155.4336600000001 55.38103000000012, 155.9144200000003 56.76792000000015, 156.75815 57.3647, 156.8103500000001 57.83204, 158.3643300000002 58.05575, 160.1506400000002 59.31477000000012, 161.87204 60.34300000000013, 163.66969 61.1409000000001, 164.4735500000001 62.55061, 163.2584200000002 62.46627, 162.65791 61.6425, 160.1214800000001 60.54423, 159.30232 61.7739600000001, 156.7206800000001 61.43442, 154.2180600000003 59.75818000000012, 155.04375 59.14495, 152.81185 58.88385, 151.2657300000003 58.78089, 151.3381500000001 59.50396, 149.78371 59.65573000000015, 148.54481 59.16448, 145.48722 59.33637, 142.1978200000002 59.03998, 138.9584800000003 57.08805, 135.12619 54.72959, 136.70171 54.60355000000013, 137.19342 53.97732, 138.1647 53.75501000000025, 138.80463 54.25455000000011, 139.90151 54.18968000000018, 141.34531 53.08957000000012, 141.37923 52.23877, 140.5974200000002 51.2396700000001, 140.51308 50.04553000000013, 140.0619300000002 48.44671000000017, 138.5547200000002 46.99965, 138.21971 46.30795, 136.86232 45.14350000000019, 135.5153500000002 43.989, 134.8693900000003 43.39821, 133.5368700000003 42.81147, 132.9062700000001 42.7984900000001, 132.2780700000003 43.28456000000011, 130.9358700000002 42.55274, 130.78 42.2200000000002, 130.6400000000002 42.395, 130.6338664084098 42.90301463477056, 131.144687941615 42.92998973242695, 131.2885551291156 44.11151968034827, 131.0251900000003 44.96796, 131.8834542176596 45.32116160743652, 133.0971200000002 45.14409, 133.7696439963132 46.11692698829916, 134.1123500000002 47.21248000000014, 134.50081 47.57845000000015, 135.0263114767868 48.47822988544391, 133.373595819228 48.18344167743484, 132.5066900000001 47.78896, 130.9872600000001 47.79013, 130.5822933289827 48.7296874049762, 129.3978178244205 49.44060008401561, 127.6574000000004 49.76027, 127.2874556824849 50.73979726826545, 126.9391565288379 51.35389415140591, 126.564399041857 51.7842554795327, 125.9463489116465 52.79279857035695, 125.0682112977105 53.16104482686893, 123.57147 53.4588, 122.2457479187931 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54.13328522400826, 70.86526655465516 55.16973358827011, 69.06816694527291 55.3852501491435, 68.16910037625891 54.97039175070438, 65.6668700000001 54.60125000000016, 65.17853356309595 54.35422781027208, 61.43660000000014 54.00625, 60.97806644068325 53.66499339457914, 61.69998619980063 52.97999644633427, 60.73999311711455 52.71998647725775, 60.92726850774025 52.44754832621501, 59.96753380721557 51.96042043721567, 61.58800337102414 51.27265879984319, 61.33742435084102 50.79907013610426, 59.93280724471558 50.84219411885184, 59.64228234237058 50.54544220641571, 58.36332000000013 51.06364, 56.77798 51.04355, 55.71694000000011 50.62171000000015, 54.5328784523762 51.02623973245937, 52.32872358583106 51.7186522487381, 50.76664839051219 51.69276235615988, 48.70238162618105 50.60512848571284, 48.57784142435762 49.87475962991564, 47.54948042174939 50.45469839131113, 46.75159630716277 49.35600576435374, 47.0436715024766 49.15203888609759, 46.4664457537763 48.39415233010493, 47.31524000000016 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47.10218984637598, 38.25511233902981 47.54640045835697, 38.77057 47.82562000000024, 39.738277622239 47.89893707945208, 39.89562000000015 48.23241, 39.67465 48.78382000000013, 40.08078901546949 49.30742991799937, 40.06904000000011 49.60105, 38.59498823421356 49.92646190042373, 38.01063113785708 49.91566152607473, 37.39345950699524 50.38395335550368, 36.62616784032539 50.22559092874513, 35.35611616388812 50.57719737405915, 35.37791 50.77394, 35.02218305841794 51.2075723333715, 34.22481570815441 51.25599315042894, 34.14197838719062 51.5664134792062, 34.39173058445724 51.76888174092591, 33.75269982273588 52.33507457133166, 32.71576053236717 52.23846548116217, 32.41205813978777 52.28869497334978, 32.15944000000022 52.06125000000011, 31.78597 52.10168, 31.54001834486226 52.74205231384644, 31.30520063652799 53.07399587667331, 31.49764 53.16743000000014, 32.30451948418838 53.13272614197285, 32.69364301934613 53.35142080343215, 32.40559858575116 53.61804535584201, 31.73127282077459 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45.5620200000001 67.01005000000021, 46.34915000000015 66.6676700000001, 47.89416000000026 66.88455000000016, 48.13876 67.52238, 50.22766000000016 67.99867000000015, 53.71743000000018 68.85738000000012, 54.47171 68.80815, 53.48582000000013 68.20131000000001, 54.72628 68.09702, 55.44268000000014 68.43866, 57.31702000000016 68.46628, 58.80200000000022 68.88082, 59.94142000000019 68.2784400000001, 61.07784000000018 68.94069, 60.03 69.52, 60.55 69.84999999999999, 63.50400000000016 69.54738999999999, 64.888115 69.23483500000015, 68.51216000000014 68.09233000000017, 69.18068 68.61563000000012, 68.16444 69.14436000000001, 68.13522 69.35648999999999, 66.93008000000012 69.45461000000012, 67.25976 69.92873, 66.72492000000014 70.70889000000014, 66.69466 71.02897000000024, 68.54006000000012 71.93450000000024, 69.19636000000011 72.84336000000016, 69.94 73.04000000000013, 72.58754 72.7762900000001, 72.79603 72.22006, 71.8481100000001 71.40898, 72.47011000000001 71.09019000000001, 72.79188000000001 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def plot_line(ob, ax, **kwargs):
    x, y = ob.xy
    ax.plot(x, y, linewidth=1, zorder=1, **kwargs)
    
def simplify(x, y, tol=8):
    return round(x, tol), round(y, tol)

def shift(x, y):
    """Sometimes x (and y) is a tuple, sometimes a float?!
    
    Note: We could also do the opposite of this to move things
    back into place...
    """
    try:
        x = [i + 360 if i < 0 else i for i in x]
    except:
        x = x + 360 if x < 0 else x
    return x, y
    
fig, (ax1, ax2, ax3) = plt.subplots(1, 3, figsize=(10, 4))

# This obviously isn't going to work...
l = ops.linemerge([a, b])
for i in l:
    plot_line(i, ax1)

# This should work, but the points are _exactly_ coincident
l = ops.linemerge([ops.transform(shift, a), b])
for i in l:
    plot_line(i, ax2)

# This _does_ work, but the process is 'destructive' (i.e., we lose precision)
l = ops.linemerge([ops.transform(simplify, ops.transform(shift, i)) for i in [a, b]])
plot_line(l, ax3)
    
plt.show()