def activeCells(self):
if getattr(self, "_activeCells", None) is None:
if getattr(self, "topofile", None) is not None:
topo = np.genfromtxt(self.basePath + self.topofile,
skip_header=1)
# Find the active cells
active = utils.surface2ind_topo(self.mesh, topo, "N")
elif isinstance(self._staticInput, float):
active = self.m0 != self._staticInput
else:
# Read from file active cells with 0:air, 1:dynamic, -1 static
active = self.activeModel != 0
inds = np.where(active)[0]
self._activeCells = inds
# Reduce m0 to active space
if len(self.m0) > len(self._activeCells):
self._m0 = self.m0[self._activeCells]
return self._activeCells
def test_Tile(self):
"""
Test for TileMap
"""
rxLocs = np.random.randn(3, 3) * 20
h = [5, 5, 5]
padDist = np.ones((3, 2)) * 100
local_meshes = []
for ii in range(rxLocs.shape[0]):
local_mesh = mesh_builder_xyz(rxLocs,
h,
padding_distance=padDist,
mesh_type="tree")
local_mesh = refine_tree_xyz(
local_mesh,
rxLocs[ii, :].reshape((1, -1)),
method="radial",
octree_levels=[1],
finalize=True,
)
local_meshes.append(local_mesh)
mesh = mesh_builder_xyz(rxLocs,
h,
padding_distance=padDist,
mesh_type="tree")
# This garantees that the local meshes are always coarser or equal
for local_mesh in local_meshes:
mesh.insert_cells(
local_mesh.gridCC,
local_mesh.cell_levels_by_index(np.arange(local_mesh.nC)),
finalize=False,
)
mesh.finalize()
# Define an active cells from topo
activeCells = utils.surface2ind_topo(mesh, rxLocs)
model = np.random.randn(int(activeCells.sum()))
total_mass = (model * mesh.vol[activeCells]).sum()
for local_mesh in local_meshes:
tile_map = maps.TileMap(
mesh,
activeCells,
local_mesh,
)
local_mass = ((tile_map * model) *
local_mesh.vol[tile_map.local_active]).sum()
self.assertTrue((local_mass - total_mass) / total_mass < 1e-8)
def test_surface2ind_topo(self):
file_url = (
"https://storage.googleapis.com/simpeg/tests/utils/vancouver_topo.xyz"
)
file2load = download(file_url)
vancouver_topo = np.loadtxt(file2load)
mesh_topo = discretize.TensorMesh(
[[(500.0, 24)], [(500.0, 20)], [(10.0, 30)]], x0="CCC")
indtopoCC = surface2ind_topo(mesh_topo,
vancouver_topo,
gridLoc="CC",
method="nearest")
indtopoN = surface2ind_topo(mesh_topo,
vancouver_topo,
gridLoc="N",
method="nearest")
assert len(np.where(indtopoCC)[0]) == 8729
assert len(np.where(indtopoN)[0]) == 8212
h,
padding_distance=padDist,
depth_core=100,
mesh_type="tree")
# This garantees that the local meshes are always coarser or equal
for local_mesh in local_meshes:
mesh.insert_cells(
local_mesh.gridCC,
local_mesh.cell_levels_by_index(np.arange(local_mesh.nC)),
finalize=False,
)
mesh.finalize()
# Define an active cells from topo
activeCells = utils.surface2ind_topo(mesh, topo)
nC = int(activeCells.sum())
# We can now create a density model and generate data
# Here a simple block in half-space
# Get the indices of the magnetized block
model = np.zeros(mesh.nC)
ind = utils.ModelBuilder.getIndicesBlock(
np.r_[-10, -10, -30],
np.r_[10, 10, -10],
mesh.gridCC,
)[0]
# Assign magnetization values
model[ind] = 0.3
def setUp(self):
# We will assume a vertical inducing field
H0 = (50000.0, 90.0, 0.0)
# The magnetization is set along a different direction (induced + remanence)
M = np.array([45.0, 90.0])
# Block with an effective susceptibility
chi_e = 0.05
# Create grid of points for topography
# Lets create a simple Gaussian topo and set the active cells
[xx, yy] = np.meshgrid(np.linspace(-200, 200, 50),
np.linspace(-200, 200, 50))
b = 100
A = 50
zz = A * np.exp(-0.5 * ((xx / b)**2.0 + (yy / b)**2.0))
topo = np.c_[mkvc(xx), mkvc(yy), mkvc(zz)]
# Create an array of observation points
xr = np.linspace(-100.0, 100.0, 20)
yr = np.linspace(-100.0, 100.0, 20)
X, Y = np.meshgrid(xr, yr)
Z = A * np.exp(-0.5 * ((X / b)**2.0 + (Y / b)**2.0)) + 10
# Create a MAGsurvey
rxLoc = np.c_[mkvc(X.T), mkvc(Y.T), mkvc(Z.T)]
rxList = magnetics.receivers.Point(rxLoc)
srcField = magnetics.sources.SourceField(receiver_list=[rxList],
parameters=H0)
survey = magnetics.survey.Survey(srcField)
###############################################################################
# Inversion Mesh
# Create a mesh
h = [5, 5, 5]
padDist = np.ones((3, 2)) * 100
mesh = mesh_builder_xyz(rxLoc,
h,
padding_distance=padDist,
depth_core=100,
mesh_type="tree")
mesh = refine_tree_xyz(mesh,
topo,
method="surface",
octree_levels=[4, 4],
finalize=True)
# Define an active cells from topo
actv = utils.surface2ind_topo(mesh, topo)
nC = int(actv.sum())
# Convert the inclination declination to vector in Cartesian
M_xyz = utils.mat_utils.dip_azimuth2cartesian(
np.ones(nC) * M[0],
np.ones(nC) * M[1])
# Get the indicies of the magnetized block
ind = utils.model_builder.getIndicesBlock(
np.r_[-20, -20, -10],
np.r_[20, 20, 25],
mesh.gridCC,
)[0]
# Assign magnetization value, inducing field strength will
# be applied in by the :class:`SimPEG.PF.Magnetics` problem
model = np.zeros(mesh.nC)
model[ind] = chi_e
# Remove air cells
model = model[actv]
# Creat reduced identity map
idenMap = maps.IdentityMap(nP=nC)
# Create the forward model operator
simulation = magnetics.Simulation3DIntegral(
survey=survey,
mesh=mesh,
chiMap=idenMap,
actInd=actv,
store_sensitivities="forward_only",
)
simulation.M = M_xyz
# Compute some data and add some random noise
synthetic_data = simulation.dpred(model)
# Split the data in components
nD = rxLoc.shape[0]
std = 5 # nT
synthetic_data += np.random.randn(nD) * std
wd = np.ones(nD) * std
# Assigne data and uncertainties to the survey
data_object = data.Data(survey, dobs=synthetic_data, noise_floor=wd)
######################################################################
# Equivalent Source
# Get the active cells for equivalent source is the top only
surf = utils.model_utils.surface_layer_index(mesh, topo)
nC = np.count_nonzero(surf) # Number of active cells
mstart = np.ones(nC) * 1e-4
# Create active map to go from reduce set to full
surfMap = maps.InjectActiveCells(mesh, surf, np.nan)
# Create identity map
idenMap = maps.IdentityMap(nP=nC)
# Create static map
simulation = magnetics.simulation.Simulation3DIntegral(
mesh=mesh,
survey=survey,
chiMap=idenMap,
actInd=surf,
store_sensitivities="ram",
)
simulation.model = mstart
# Create a regularization function, in this case l2l2
reg = regularization.Sparse(mesh,
indActive=surf,
mapping=maps.IdentityMap(nP=nC),
alpha_z=0)
reg.mref = np.zeros(nC)
# Specify how the optimization will proceed, set susceptibility bounds to inf
opt = optimization.ProjectedGNCG(
maxIter=10,
lower=-np.inf,
upper=np.inf,
maxIterLS=5,
maxIterCG=5,
tolCG=1e-3,
)
# Define misfit function (obs-calc)
dmis = data_misfit.L2DataMisfit(simulation=simulation,
data=data_object)
# Create the default L2 inverse problem from the above objects
invProb = inverse_problem.BaseInvProblem(dmis, reg, opt)
# Specify how the initial beta is found
betaest = directives.BetaEstimate_ByEig(beta0_ratio=2)
# Target misfit to stop the inversion,
# try to fit as much as possible of the signal, we don't want to lose anything
IRLS = directives.Update_IRLS(f_min_change=1e-3,
minGNiter=1,
beta_tol=1e-1,
max_irls_iterations=5)
update_Jacobi = directives.UpdatePreconditioner()
# Put all the parts together
inv = inversion.BaseInversion(
invProb, directiveList=[betaest, IRLS, update_Jacobi])
# Run the equivalent source inversion
print("Solving for Equivalent Source")
mrec = inv.run(mstart)
########################################################
# Forward Amplitude Data
# ----------------------
#
# Now that we have an equialent source layer, we can forward model alh three
# components of the field and add them up: :math:`|B| = \sqrt{( Bx^2 + Bx^2 + Bx^2 )}`
#
rxList = magnetics.receivers.Point(rxLoc,
components=["bx", "by", "bz"])
srcField = magnetics.sources.SourceField(receiver_list=[rxList],
parameters=H0)
surveyAmp = magnetics.survey.Survey(srcField)
simulation = magnetics.simulation.Simulation3DIntegral(
mesh=mesh,
survey=surveyAmp,
chiMap=idenMap,
actInd=surf,
is_amplitude_data=True,
store_sensitivities="forward_only",
)
bAmp = simulation.fields(mrec)
######################################################################
# Amplitude Inversion
# -------------------
#
# Now that we have amplitude data, we can invert for an effective
# susceptibility. This is a non-linear inversion.
#
# Create active map to go from reduce space to full
actvMap = maps.InjectActiveCells(mesh, actv, -100)
nC = int(actv.sum())
# Create identity map
idenMap = maps.IdentityMap(nP=nC)
mstart = np.ones(nC) * 1e-4
# Create the forward model operator
simulation = magnetics.simulation.Simulation3DIntegral(
survey=surveyAmp,
mesh=mesh,
chiMap=idenMap,
actInd=actv,
is_amplitude_data=True,
)
data_obj = data.Data(survey, dobs=bAmp, noise_floor=wd)
# Create a sparse regularization
reg = regularization.Sparse(mesh, indActive=actv, mapping=idenMap)
reg.norms = np.c_[1, 0, 0, 0]
reg.mref = np.zeros(nC)
# Data misfit function
dmis = data_misfit.L2DataMisfit(simulation=simulation, data=data_obj)
# Add directives to the inversion
opt = optimization.ProjectedGNCG(maxIter=10,
lower=0.0,
upper=1.0,
maxIterLS=5,
maxIterCG=5,
tolCG=1e-3)
invProb = inverse_problem.BaseInvProblem(dmis, reg, opt)
# Here is the list of directives
betaest = directives.BetaEstimate_ByEig(beta0_ratio=1)
# Specify the sparse norms
IRLS = directives.Update_IRLS(
max_irls_iterations=5,
f_min_change=1e-3,
minGNiter=1,
coolingRate=1,
beta_search=False,
)
# Special directive specific to the mag amplitude problem. The sensitivity
# weights are update between each iteration.
update_SensWeight = directives.UpdateSensitivityWeights()
update_Jacobi = directives.UpdatePreconditioner()
# Put all together
self.inv = inversion.BaseInversion(
invProb,
directiveList=[update_SensWeight, betaest, IRLS, update_Jacobi])
self.mstart = mstart
self.model = model
self.sim = simulation
# Finalize the mesh mesh.finalize() ####################################################### # Project Electrodes to Discretized Topography # -------------------------------------------- # # It is important that electrodes are not modeled as being in the air. Even if the # electrodes are properly located along surface topography, they may lie above # the discretized topography. This step is carried out to ensure all electrodes # lie on the discretized surface. # # Find cells that lie below surface topography ind_active = surface2ind_topo(mesh, topo_xyz) # Extract survey from data object dc_survey = dc_data.survey ip_survey = ip_data.survey # Shift electrodes to the surface of discretized topography dc_survey.drape_electrodes_on_topography(mesh, ind_active, option="top") ip_survey.drape_electrodes_on_topography(mesh, ind_active, option="top") # Reset survey in data object dc_data.survey = dc_survey ip_data.survey = ip_survey ################################################################# # Starting/Reference Model and Mapping on OcTree Mesh
def run(plotIt=True, survey_type="dipole-dipole", p=0.0, qx=2.0, qz=2.0):
np.random.seed(1)
# Initiate I/O class for DC
IO = DC.IO()
# Obtain ABMN locations
xmin, xmax = 0.0, 200.0
ymin, ymax = 0.0, 0.0
zmin, zmax = 0, 0
endl = np.array([[xmin, ymin, zmin], [xmax, ymax, zmax]])
# Generate DC survey object
survey = gen_DCIPsurvey(endl,
survey_type=survey_type,
dim=2,
a=10,
b=10,
n=10)
survey = IO.from_abmn_locations_to_survey(
survey.locations_a,
survey.locations_b,
survey.locations_m,
survey.locations_n,
survey_type,
data_dc_type="volt",
)
# Obtain 2D TensorMesh
mesh, actind = IO.set_mesh()
topo, mesh1D = genTopography(mesh, -10, 0, its=100)
actind = utils.surface2ind_topo(mesh, np.c_[mesh1D.vectorCCx, topo])
survey.drape_electrodes_on_topography(mesh, actind, option="top")
# Build a conductivity model
blk_inds_c = utils.model_builder.getIndicesSphere(np.r_[60.0, -25.0], 12.5,
mesh.gridCC)
blk_inds_r = utils.model_builder.getIndicesSphere(np.r_[140.0, -25.0],
12.5, mesh.gridCC)
layer_inds = mesh.gridCC[:, 1] > -5.0
sigma = np.ones(mesh.nC) * 1.0 / 100.0
sigma[blk_inds_c] = 1.0 / 10.0
sigma[blk_inds_r] = 1.0 / 1000.0
sigma[~actind] = 1.0 / 1e8
rho = 1.0 / sigma
# Show the true conductivity model
if plotIt:
fig = plt.figure(figsize=(12, 3))
ax = plt.subplot(111)
temp = rho.copy()
temp[~actind] = np.nan
out = mesh.plotImage(
temp,
grid=True,
ax=ax,
gridOpts={"alpha": 0.2},
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
)
ax.plot(survey.electrode_locations[:, 0],
survey.electrode_locations[:, 1], "k.")
ax.set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
ax.set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
cb = plt.colorbar(out[0])
cb.set_label("Resistivity (ohm-m)")
ax.set_aspect("equal")
plt.show()
# Use Exponential Map: m = log(rho)
actmap = maps.InjectActiveCells(mesh,
indActive=actind,
valInactive=np.log(1e8))
mapping = maps.ExpMap(mesh) * actmap
# Generate mtrue
mtrue = np.log(rho[actind])
# Generate 2.5D DC problem
# "N" means potential is defined at nodes
prb = DC.Simulation2DNodal(mesh,
survey=survey,
rhoMap=mapping,
storeJ=True,
Solver=Solver,
verbose=True)
# Make synthetic DC data with 5% Gaussian noise
data = prb.make_synthetic_data(mtrue, relative_error=0.05, add_noise=True)
IO.data_dc = data.dobs
# Show apparent resisitivty pseudo-section
if plotIt:
IO.plotPseudoSection(data=data.dobs / IO.G,
data_type="apparent_resistivity")
# Show apparent resisitivty histogram
if plotIt:
fig = plt.figure()
out = hist(data.dobs / IO.G, bins=20)
plt.xlabel("Apparent Resisitivty ($\Omega$m)")
plt.show()
# Set initial model based upon histogram
m0 = np.ones(actmap.nP) * np.log(100.0)
# Set standard_deviation
# floor
eps = 10**(-3.2)
# percentage
relative = 0.05
dmisfit = data_misfit.L2DataMisfit(simulation=prb, data=data)
uncert = abs(data.dobs) * relative + eps
dmisfit.standard_deviation = uncert
# Map for a regularization
regmap = maps.IdentityMap(nP=int(actind.sum()))
# Related to inversion
reg = regularization.Sparse(mesh,
indActive=actind,
mapping=regmap,
gradientType="components")
# gradientType = 'components'
reg.norms = np.c_[p, qx, qz, 0.0]
IRLS = directives.Update_IRLS(max_irls_iterations=20,
minGNiter=1,
beta_search=False,
fix_Jmatrix=True)
opt = optimization.InexactGaussNewton(maxIter=40)
invProb = inverse_problem.BaseInvProblem(dmisfit, reg, opt)
beta = directives.BetaSchedule(coolingFactor=5, coolingRate=2)
betaest = directives.BetaEstimate_ByEig(beta0_ratio=1e0)
target = directives.TargetMisfit()
update_Jacobi = directives.UpdatePreconditioner()
inv = inversion.BaseInversion(invProb, directiveList=[betaest, IRLS])
prb.counter = opt.counter = utils.Counter()
opt.LSshorten = 0.5
opt.remember("xc")
# Run inversion
mopt = inv.run(m0)
rho_est = mapping * mopt
rho_est_l2 = mapping * invProb.l2model
rho_est[~actind] = np.nan
rho_est_l2[~actind] = np.nan
rho_true = rho.copy()
rho_true[~actind] = np.nan
# show recovered conductivity
if plotIt:
vmin, vmax = rho.min(), rho.max()
fig, ax = plt.subplots(3, 1, figsize=(20, 9))
out1 = mesh.plotImage(
rho_true,
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
ax=ax[0],
)
out2 = mesh.plotImage(
rho_est_l2,
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
ax=ax[1],
)
out3 = mesh.plotImage(
rho_est,
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
ax=ax[2],
)
out = [out1, out2, out3]
titles = ["True", "L2", ("L%d, Lx%d, Lz%d") % (p, qx, qz)]
for i in range(3):
ax[i].plot(survey.electrode_locations[:, 0],
survey.electrode_locations[:, 1], "kv")
ax[i].set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
ax[i].set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
cb = plt.colorbar(out[i][0], ax=ax[i])
cb.set_label("Resistivity ($\Omega$m)")
ax[i].set_xlabel("Northing (m)")
ax[i].set_ylabel("Elevation (m)")
ax[i].set_aspect("equal")
ax[i].set_title(titles[i])
plt.tight_layout()
plt.show()
def run(plotIt=True, survey_type="dipole-dipole"):
np.random.seed(1)
# Initiate I/O class for DC
IO = DC.IO()
# Obtain ABMN locations
xmin, xmax = 0.0, 200.0
ymin, ymax = 0.0, 0.0
zmin, zmax = 0, 0
endl = np.array([[xmin, ymin, zmin], [xmax, ymax, zmax]])
# Generate DC survey object
survey = gen_DCIPsurvey(endl,
survey_type=survey_type,
dim=2,
a=10,
b=10,
n=10)
survey = IO.from_ambn_locations_to_survey(
survey.locations_a,
survey.locations_b,
survey.locations_m,
survey.locations_n,
survey_type,
data_dc_type="volt",
)
# Obtain 2D TensorMesh
mesh, actind = IO.set_mesh()
topo, mesh1D = genTopography(mesh, -10, 0, its=100)
actind = utils.surface2ind_topo(mesh, np.c_[mesh1D.vectorCCx, topo])
survey.drape_electrodes_on_topography(mesh, actind, option="top")
# Build a conductivity model
blk_inds_c = utils.model_builder.getIndicesSphere(np.r_[60.0, -25.0], 12.5,
mesh.gridCC)
blk_inds_r = utils.model_builder.getIndicesSphere(np.r_[140.0, -25.0],
12.5, mesh.gridCC)
layer_inds = mesh.gridCC[:, 1] > -5.0
sigma = np.ones(mesh.nC) * 1.0 / 100.0
sigma[blk_inds_c] = 1.0 / 10.0
sigma[blk_inds_r] = 1.0 / 1000.0
sigma[~actind] = 1.0 / 1e8
rho = 1.0 / sigma
# Show the true conductivity model
if plotIt:
fig = plt.figure(figsize=(12, 3))
ax = plt.subplot(111)
temp = rho.copy()
temp[~actind] = np.nan
out = mesh.plotImage(
temp,
grid=True,
ax=ax,
gridOpts={"alpha": 0.2},
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
)
ax.plot(survey.electrode_locations[:, 0],
survey.electrode_locations[:, 1], "k.")
ax.set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
ax.set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
cb = plt.colorbar(out[0])
cb.set_label("Resistivity (ohm-m)")
ax.set_aspect("equal")
plt.show()
# Use Exponential Map: m = log(rho)
actmap = maps.InjectActiveCells(mesh,
indActive=actind,
valInactive=np.log(1e8))
mapping = maps.ExpMap(mesh) * actmap
# Generate mtrue
mtrue = np.log(rho[actind])
# Generate 2.5D DC problem
# "N" means potential is defined at nodes
prb = DC.Simulation2DNodal(mesh,
survey=survey,
rhoMap=mapping,
storeJ=True,
Solver=Solver,
verbose=True)
geometric_factor = survey.set_geometric_factor(
data_type="apparent_resistivity",
survey_type="dipole-dipole",
space_type="half-space",
)
# Make synthetic DC data with 5% Gaussian noise
data = prb.make_synthetic_data(mtrue, relative_error=0.05, add_noise=True)
IO.data_dc = data.dobs
# Show apparent resisitivty pseudo-section
if plotIt:
IO.plotPseudoSection(data=data.dobs, data_type="apparent_resistivity")
# Show apparent resisitivty histogram
if plotIt:
fig = plt.figure()
out = hist(data.dobs, bins=20)
plt.xlabel("Apparent Resisitivty ($\Omega$m)")
plt.show()
# Set initial model based upon histogram
m0 = np.ones(actmap.nP) * np.log(100.0)
# Set standard_deviation
# floor (10 ohm-m)
eps = 1.0
# percentage
relative = 0.05
dmisfit = data_misfit.L2DataMisfit(simulation=prb, data=data)
uncert = abs(data.dobs) * relative + eps
dmisfit.standard_deviation = uncert
# Map for a regularization
regmap = maps.IdentityMap(nP=int(actind.sum()))
# Related to inversion
reg = regularization.Sparse(mesh, indActive=actind, mapping=regmap)
opt = optimization.InexactGaussNewton(maxIter=15)
invProb = inverse_problem.BaseInvProblem(dmisfit, reg, opt)
beta = directives.BetaSchedule(coolingFactor=5, coolingRate=2)
betaest = directives.BetaEstimate_ByEig(beta0_ratio=1e0)
target = directives.TargetMisfit()
updateSensW = directives.UpdateSensitivityWeights()
update_Jacobi = directives.UpdatePreconditioner()
inv = inversion.BaseInversion(
invProb,
directiveList=[beta, target, updateSensW, betaest, update_Jacobi])
prb.counter = opt.counter = utils.Counter()
opt.LSshorten = 0.5
opt.remember("xc")
# Run inversion
mopt = inv.run(m0)
# Get diag(JtJ)
mask_inds = np.ones(mesh.nC, dtype=bool)
jtj = np.sqrt(updateSensW.JtJdiag[0])
jtj /= jtj.max()
temp = np.ones_like(jtj, dtype=bool)
temp[jtj > 0.005] = False
mask_inds[actind] = temp
actind_final = np.logical_and(actind, ~mask_inds)
jtj_cc = np.ones(mesh.nC) * np.nan
jtj_cc[actind] = jtj
# Show the sensitivity
if plotIt:
fig = plt.figure(figsize=(12, 3))
ax = plt.subplot(111)
temp = rho.copy()
temp[~actind] = np.nan
out = mesh.plotImage(
jtj_cc,
grid=True,
ax=ax,
gridOpts={"alpha": 0.2},
clim=(0.005, 0.5),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
)
ax.plot(survey.electrode_locations[:, 0],
survey.electrode_locations[:, 1], "k.")
ax.set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
ax.set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
cb = plt.colorbar(out[0])
cb.set_label("Sensitivity")
ax.set_aspect("equal")
plt.show()
# Convert obtained inversion model to resistivity
# rho = M(m), where M(.) is a mapping
rho_est = mapping * mopt
rho_est[~actind_final] = np.nan
rho_true = rho.copy()
rho_true[~actind_final] = np.nan
# show recovered conductivity
if plotIt:
vmin, vmax = rho.min(), rho.max()
fig, ax = plt.subplots(2, 1, figsize=(20, 6))
out1 = mesh.plotImage(
rho_true,
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
ax=ax[0],
)
out2 = mesh.plotImage(
rho_est,
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
ax=ax[1],
)
out = [out1, out2]
for i in range(2):
ax[i].plot(survey.electrode_locations[:, 0],
survey.electrode_locations[:, 1], "kv")
ax[i].set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
ax[i].set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
cb = plt.colorbar(out[i][0], ax=ax[i])
cb.set_label("Resistivity ($\Omega$m)")
ax[i].set_xlabel("Northing (m)")
ax[i].set_ylabel("Elevation (m)")
ax[i].set_aspect("equal")
plt.tight_layout()
plt.show()
# -----------------------------------------------------
#
# It is important that electrodes are not modeled as being in the air. Even if the
# electrodes are properly located along surface topography, they may lie above
# the discretized topography. This step is carried out to ensure all electrodes
# lie on the discretized surface.
#
# Define conductivity model in S/m (or resistivity model in Ohm m)
air_conductivity = 1e-8
background_conductivity = 1e-2
conductor_conductivity = 1e-1
resistor_conductivity = 1e-3
# Find active cells in forward modeling (cell below surface)
ind_active = surface2ind_topo(mesh, xyz_topo[:, [0, 2]])
# Define mapping from model to active cells
nC = int(ind_active.sum())
conductivity_map = maps.InjectActiveCells(mesh, ind_active, air_conductivity)
# Define model
conductivity_model = background_conductivity * np.ones(nC)
ind_conductor = model_builder.getIndicesSphere(np.r_[-120.0, -180.0], 60.0,
mesh.gridCC)
ind_conductor = ind_conductor[ind_active]
conductivity_model[ind_conductor] = conductor_conductivity
ind_resistor = model_builder.getIndicesSphere(np.r_[120.0, -180.0], 60.0,
mesh.gridCC)
h = [5, 5, 5]
padDist = np.ones((3, 2)) * 100
mesh = mesh_builder_xyz(xyzLoc,
h,
padding_distance=padDist,
depth_core=100,
mesh_type="tree")
mesh = refine_tree_xyz(mesh,
topo,
method="surface",
octree_levels=[4, 4],
finalize=True)
# Define an active cells from topo
actv = utils.surface2ind_topo(mesh, topo)
nC = int(actv.sum())
###########################################################################
# A simple function to plot vectors in TreeMesh
#
# Should eventually end up on discretize
#
def plotVectorSectionsOctree(
mesh,
m,
normal="X",
ind=0,
vmin=None,
def setUp(self):
np.random.seed(0)
# First we need to define the direction of the inducing field
# As a simple case, we pick a vertical inducing field of magnitude
# 50,000nT.
# From old convention, field orientation is given as an
# azimuth from North (positive clockwise)
# and dip from the horizontal (positive downward).
H0 = (50000.0, 90.0, 0.0)
# Create a mesh
h = [5, 5, 5]
padDist = np.ones((3, 2)) * 100
nCpad = [2, 4, 2]
# Create grid of points for topography
# Lets create a simple Gaussian topo and set the active cells
[xx, yy] = np.meshgrid(np.linspace(-200.0, 200.0, 50),
np.linspace(-200.0, 200.0, 50))
b = 100
A = 50
zz = A * np.exp(-0.5 * ((xx / b)**2.0 + (yy / b)**2.0))
# We would usually load a topofile
topo = np.c_[utils.mkvc(xx), utils.mkvc(yy), utils.mkvc(zz)]
# Create and array of observation points
xr = np.linspace(-100.0, 100.0, 20)
yr = np.linspace(-100.0, 100.0, 20)
X, Y = np.meshgrid(xr, yr)
Z = A * np.exp(-0.5 * ((X / b)**2.0 + (Y / b)**2.0)) + 5
# Create a MAGsurvey
xyzLoc = np.c_[utils.mkvc(X.T), utils.mkvc(Y.T), utils.mkvc(Z.T)]
rxLoc = mag.Point(xyzLoc)
srcField = mag.SourceField([rxLoc], parameters=H0)
survey = mag.Survey(srcField)
# self.mesh.finalize()
self.mesh = meshutils.mesh_builder_xyz(
xyzLoc,
h,
padding_distance=padDist,
mesh_type="TREE",
)
self.mesh = meshutils.refine_tree_xyz(
self.mesh,
topo,
method="surface",
octree_levels=nCpad,
octree_levels_padding=nCpad,
finalize=True,
)
# Define an active cells from topo
actv = utils.surface2ind_topo(self.mesh, topo)
nC = int(actv.sum())
# We can now create a susceptibility model and generate data
# Lets start with a simple block in half-space
self.model = utils.model_builder.addBlock(
self.mesh.gridCC,
np.zeros(self.mesh.nC),
np.r_[-20, -20, -15],
np.r_[20, 20, 20],
0.05,
)[actv]
# Create active map to go from reduce set to full
self.actvMap = maps.InjectActiveCells(self.mesh, actv, np.nan)
# Creat reduced identity map
idenMap = maps.IdentityMap(nP=nC)
# Create the forward model operator
sim = mag.Simulation3DIntegral(
self.mesh,
survey=survey,
chiMap=idenMap,
actInd=actv,
store_sensitivities="ram",
)
self.sim = sim
data = sim.make_synthetic_data(self.model,
relative_error=0.0,
noise_floor=1.0,
add_noise=True)
# Create a regularization
reg = regularization.Sparse(self.mesh, indActive=actv, mapping=idenMap)
reg.norms = np.c_[0, 0, 0, 0]
reg.mref = np.zeros(nC)
# Data misfit function
dmis = data_misfit.L2DataMisfit(simulation=sim, data=data)
# Add directives to the inversion
opt = optimization.ProjectedGNCG(
maxIter=10,
lower=0.0,
upper=10.0,
maxIterLS=5,
maxIterCG=5,
tolCG=1e-4,
stepOffBoundsFact=1e-4,
)
invProb = inverse_problem.BaseInvProblem(dmis, reg, opt, beta=1e6)
# Here is where the norms are applied
# Use pick a treshold parameter empirically based on the distribution of
# model parameters
IRLS = directives.Update_IRLS(f_min_change=1e-3,
max_irls_iterations=20,
beta_tol=1e-1,
beta_search=False)
update_Jacobi = directives.UpdatePreconditioner()
sensitivity_weights = directives.UpdateSensitivityWeights()
self.inv = inversion.BaseInversion(
invProb, directiveList=[IRLS, sensitivity_weights, update_Jacobi])
def iterator(mesh,
domain,
surface,
cell_width,
objct,
coordinates,
receiver_locations,
source_locations,
survey,
par_background,
par_object,
ind_object,
frequency=1,
omega=2 * np.pi,
parameter='resistivity',
interpolation='rbf',
type_object='block',
lim_iterations=5,
factor_object=2,
factor_receiver=3,
factor_source=3,
refine_percentage=0.05,
axis='x',
degrees_rad=0,
radius=1,
Ex=None,
Ey=None,
Ez=None,
diff_list=np.array([[0, 0]]),
r_a_o_list=None,
r_a_r_list=None,
r_a_s_list=None):
"""An iteration scheme that implements an error estimator to adaptively refine
a mesh, in order to reduce the error of the electric field solution.
This function is mainly used for small objects in a domain.
If you want to continue from previous iteration, you have to give the mesh, field values,
convergence list and previous refinements as input arguments."""
# Find cells that are active in the forward modeling (cells below surface)
ind_active = surface2ind_topo(mesh, surface)
# Define mapping from model to active cells
model_map = maps.InjectActiveCells(mesh, ind_active, par_background)
# Define model. Models in SimPEG are vector arrays
model = par_background * np.ones(ind_active.sum())
if type_object == 'block':
ind_object = get_ind_block(mesh, ind_active, coordinates, axis,
degrees_rad)
if type_object == 'sphere':
ind_object = get_ind_sphere(mesh, ind_active, coordinates, radius)
model[ind_object] = par_object
diff = 10
if diff_list[0, 0] == 0:
i = 0
av_diff_list = []
refine_at_object_list = []
refine_at_receivers_list = []
refine_at_sources_list = []
# Starting after the pause
else:
i = diff_list[-1, 0]
av_diff_list = list(diff_list)
refine_at_object_list = r_a_o_list
refine_at_receivers_list = r_a_r_list
refine_at_sources_list = r_a_s_list
lim_iterations = lim_iterations + i
ef_old_x = Ex
ef_old_y = Ey
ef_old_z = Ez
def ef_interpolator(x):
return np.array([ef_x(*x), ef_y(*x), ef_z(*x)])
def ef_old_interpolator(x):
return np.array([ef_old_x(*x), ef_old_y(*x), ef_old_z(*x)])
while diff > 0.01 and i < lim_iterations:
# Maximum relative difference between current and previous iteration should fall below 1% in order to converge.
# Define search areas
search_area_obj = search_area_object(mesh, objct, factor=factor_object)
search_area_receiv = search_area_receivers(mesh,
receiver_locations,
factor=factor_receiver)
search_area_sourc = search_area_sources(mesh,
source_locations,
factor=factor_source)
# Interpolate curl and electric field
curl_x, curl_y, curl_z, ef_x, ef_y, ef_z = estimate_curl_electric_field(
mesh,
survey,
model_map,
model,
interpolation=interpolation,
frequency=frequency,
omega=omega,
parameter=parameter)
# Compare electric field values until relative difference falls below 1%
if diff_list[0, 0] == 0:
if i > 0:
relative_difference_Efield = []
for cell in search_area_obj:
# This equation is sensitive to catastrophic failure
form = np.abs(
(ef_old_interpolator(cell) - ef_interpolator(cell)) /
ef_old_interpolator(cell))
relative_difference_Efield.append(np.linalg.norm(form))
for cell in search_area_receiv:
# This equation is sensitive to catastrophic failure
form = np.abs(
(ef_old_interpolator(cell) - ef_interpolator(cell)) /
ef_old_interpolator(cell))
relative_difference_Efield.append(np.linalg.norm(form))
for cell in search_area_sourc:
# This equation is sensitive to catastrophic failure
form = np.abs(
(ef_old_interpolator(cell) - ef_interpolator(cell)) /
ef_old_interpolator(cell))
relative_difference_Efield.append(np.linalg.norm(form))
diff = sum(relative_difference_Efield) / len(
relative_difference_Efield)
av_diff_list.append([i + 1, diff])
print("Average relative difference is ", diff)
else:
relative_difference_Efield = []
for cell in search_area_obj:
# This equation is sensitive to catastrophic failure
form = np.abs(
(ef_old_interpolator(cell) - ef_interpolator(cell)) /
ef_old_interpolator(cell))
relative_difference_Efield.append(np.linalg.norm(form))
for cell in search_area_receiv:
# This equation is sensitive to catastrophic failure
form = np.abs(
(ef_old_interpolator(cell) - ef_interpolator(cell)) /
ef_old_interpolator(cell))
relative_difference_Efield.append(np.linalg.norm(form))
for cell in search_area_sourc:
# This equation is sensitive to catastrophic failure
form = np.abs(
(ef_old_interpolator(cell) - ef_interpolator(cell)) /
ef_old_interpolator(cell))
relative_difference_Efield.append(np.linalg.norm(form))
diff = sum(relative_difference_Efield) / len(
relative_difference_Efield)
av_diff_list.append([i + 1, diff])
print("Average relative difference is ", diff)
ef_old_x = ef_x
ef_old_y = ef_y
ef_old_z = ef_z
# Define cells to refine near object
cells_to_refine_object = estimate_error(
search_area_obj,
curl_x,
curl_y,
curl_z,
ef_x,
ef_y,
ef_z,
refine_percentage=refine_percentage)
refine_at_object_list.append(cells_to_refine_object)
# Define cells to refine near receivers
cells_to_refine_receivers = estimate_error(
search_area_receiv,
curl_x,
curl_y,
curl_z,
ef_x,
ef_y,
ef_z,
refine_percentage=refine_percentage)
refine_at_receivers_list.append(cells_to_refine_receivers)
# Define cells to refine near sources
cells_to_refine_sources = estimate_error(
search_area_sourc,
curl_x,
curl_y,
curl_z,
ef_x,
ef_y,
ef_z,
refine_percentage=refine_percentage)
refine_at_sources_list.append(cells_to_refine_sources)
# Refine the mesh
mesh = create_octree_mesh(domain, cell_width, objct, 'surface')
refine_at_locations(mesh, source_locations)
refine_at_locations(mesh, receiver_locations)
for refo in refine_at_object_list:
refine_at_locations(mesh, refo)
for refr in refine_at_receivers_list:
refine_at_locations(mesh, refr)
for refs in refine_at_sources_list:
refine_at_locations(mesh, refs)
mesh.finalize()
# Find cells that are active in the forward modeling (cells below surface)
ind_active = surface2ind_topo(mesh, surface)
# Define mapping from model to active cells
model_map = maps.InjectActiveCells(mesh, ind_active, par_background)
# Define model. Models in SimPEG are vector arrays
model = par_background * np.ones(ind_active.sum())
if type_object == 'block':
ind_object = get_ind_block(mesh, ind_active, coordinates)
if type_object == 'sphere':
ind_object = get_ind_sphere(mesh, ind_active, coordinates, radius)
model[ind_object] = par_object
print(i)
i += 1
if diff < 0.01:
return mesh, ef_x, ef_y, ef_z, np.array(av_diff_list)
else:
return mesh, ef_x, ef_y, ef_z, np.array(
av_diff_list
), refine_at_object_list, refine_at_receivers_list, refine_at_sources_list
def setUp(self):
np.random.seed(0)
H0 = (50000.0, 90.0, 0.0)
# The magnetization is set along a different
# direction (induced + remanence)
M = np.array([45.0, 90.0])
# Create grid of points for topography
# Lets create a simple Gaussian topo
# and set the active cells
[xx, yy] = np.meshgrid(np.linspace(-200, 200, 50),
np.linspace(-200, 200, 50))
b = 100
A = 50
zz = A * np.exp(-0.5 * ((xx / b)**2.0 + (yy / b)**2.0))
# We would usually load a topofile
topo = np.c_[utils.mkvc(xx), utils.mkvc(yy), utils.mkvc(zz)]
# Create and array of observation points
xr = np.linspace(-100.0, 100.0, 20)
yr = np.linspace(-100.0, 100.0, 20)
X, Y = np.meshgrid(xr, yr)
Z = A * np.exp(-0.5 * ((X / b)**2.0 + (Y / b)**2.0)) + 5
# Create a MAGsurvey
xyzLoc = np.c_[utils.mkvc(X.T), utils.mkvc(Y.T), utils.mkvc(Z.T)]
rxLoc = mag.Point(xyzLoc)
srcField = mag.SourceField([rxLoc], parameters=H0)
survey = mag.Survey(srcField)
# Create a mesh
h = [5, 5, 5]
padDist = np.ones((3, 2)) * 100
mesh = mesh_builder_xyz(xyzLoc,
h,
padding_distance=padDist,
depth_core=100,
mesh_type="tree")
mesh = refine_tree_xyz(mesh,
topo,
method="surface",
octree_levels=[4, 4],
finalize=True)
self.mesh = mesh
# Define an active cells from topo
actv = utils.surface2ind_topo(mesh, topo)
nC = int(actv.sum())
model = np.zeros((mesh.nC, 3))
# Convert the inclination declination to vector in Cartesian
M_xyz = utils.mat_utils.dip_azimuth2cartesian(M[0], M[1])
# Get the indicies of the magnetized block
ind = utils.model_builder.getIndicesBlock(
np.r_[-20, -20, -10],
np.r_[20, 20, 25],
mesh.gridCC,
)[0]
# Assign magnetization values
model[ind, :] = np.kron(np.ones((ind.shape[0], 1)), M_xyz * 0.05)
# Remove air cells
self.model = model[actv, :]
# Create active map to go from reduce set to full
self.actvMap = maps.InjectActiveCells(mesh, actv, np.nan)
# Creat reduced identity map
idenMap = maps.IdentityMap(nP=nC * 3)
# Create the forward model operator
sim = mag.Simulation3DIntegral(
self.mesh,
survey=survey,
model_type="vector",
chiMap=idenMap,
actInd=actv,
store_sensitivities="disk",
)
self.sim = sim
# Compute some data and add some random noise
data = sim.make_synthetic_data(utils.mkvc(self.model),
relative_error=0.0,
noise_floor=5.0,
add_noise=True)
# This Mapping connects the regularizations for the three-component
# vector model
wires = maps.Wires(("p", nC), ("s", nC), ("t", nC))
# Create three regularization for the different components
# of magnetization
reg_p = regularization.Sparse(mesh, indActive=actv, mapping=wires.p)
reg_p.mref = np.zeros(3 * nC)
reg_s = regularization.Sparse(mesh, indActive=actv, mapping=wires.s)
reg_s.mref = np.zeros(3 * nC)
reg_t = regularization.Sparse(mesh, indActive=actv, mapping=wires.t)
reg_t.mref = np.zeros(3 * nC)
reg = reg_p + reg_s + reg_t
reg.mref = np.zeros(3 * nC)
# Data misfit function
dmis = data_misfit.L2DataMisfit(simulation=sim, data=data)
# dmis.W = 1./survey.std
# Add directives to the inversion
opt = optimization.ProjectedGNCG(maxIter=10,
lower=-10,
upper=10.0,
maxIterLS=5,
maxIterCG=5,
tolCG=1e-4)
invProb = inverse_problem.BaseInvProblem(dmis, reg, opt)
# A list of directive to control the inverson
betaest = directives.BetaEstimate_ByEig(beta0_ratio=1e1)
# Here is where the norms are applied
# Use pick a treshold parameter empirically based on the distribution of
# model parameters
IRLS = directives.Update_IRLS(f_min_change=1e-3,
max_irls_iterations=0,
beta_tol=5e-1)
# Pre-conditioner
update_Jacobi = directives.UpdatePreconditioner()
sensitivity_weights = directives.UpdateSensitivityWeights(
everyIter=False)
inv = inversion.BaseInversion(
invProb,
directiveList=[sensitivity_weights, IRLS, update_Jacobi, betaest])
# Run the inversion
m0 = np.ones(3 * nC) * 1e-4 # Starting model
mrec_MVIC = inv.run(m0)
sim.chiMap = maps.SphericalSystem(nP=nC * 3)
self.mstart = sim.chiMap.inverse(mrec_MVIC)
dmis.simulation.model = self.mstart
beta = invProb.beta
# Create a block diagonal regularization
wires = maps.Wires(("amp", nC), ("theta", nC), ("phi", nC))
# Create a Combo Regularization
# Regularize the amplitude of the vectors
reg_a = regularization.Sparse(mesh, indActive=actv, mapping=wires.amp)
reg_a.norms = np.c_[0.0, 0.0, 0.0,
0.0] # Sparse on the model and its gradients
reg_a.mref = np.zeros(3 * nC)
# Regularize the vertical angle of the vectors
reg_t = regularization.Sparse(mesh,
indActive=actv,
mapping=wires.theta)
reg_t.alpha_s = 0.0 # No reference angle
reg_t.space = "spherical"
reg_t.norms = np.c_[2.0, 0.0, 0.0, 0.0] # Only norm on gradients used
# Regularize the horizontal angle of the vectors
reg_p = regularization.Sparse(mesh, indActive=actv, mapping=wires.phi)
reg_p.alpha_s = 0.0 # No reference angle
reg_p.space = "spherical"
reg_p.norms = np.c_[2.0, 0.0, 0.0, 0.0] # Only norm on gradients used
reg = reg_a + reg_t + reg_p
reg.mref = np.zeros(3 * nC)
Lbound = np.kron(np.asarray([0, -np.inf, -np.inf]), np.ones(nC))
Ubound = np.kron(np.asarray([10, np.inf, np.inf]), np.ones(nC))
# Add directives to the inversion
opt = optimization.ProjectedGNCG(
maxIter=5,
lower=Lbound,
upper=Ubound,
maxIterLS=5,
maxIterCG=5,
tolCG=1e-3,
stepOffBoundsFact=1e-3,
)
opt.approxHinv = None
invProb = inverse_problem.BaseInvProblem(dmis, reg, opt, beta=beta)
# Here is where the norms are applied
IRLS = directives.Update_IRLS(
f_min_change=1e-4,
max_irls_iterations=5,
minGNiter=1,
beta_tol=0.5,
coolingRate=1,
coolEps_q=True,
sphericalDomain=True,
)
# Special directive specific to the mag amplitude problem. The sensitivity
# weights are update between each iteration.
ProjSpherical = directives.ProjectSphericalBounds()
sensitivity_weights = directives.UpdateSensitivityWeights()
update_Jacobi = directives.UpdatePreconditioner()
self.inv = inversion.BaseInversion(
invProb,
directiveList=[
ProjSpherical, IRLS, sensitivity_weights, update_Jacobi
],
)
def setUp(self):
ndv = -100
# Create a self.mesh
dx = 5.0
hxind = [(dx, 5, -1.3), (dx, 5), (dx, 5, 1.3)]
hyind = [(dx, 5, -1.3), (dx, 5), (dx, 5, 1.3)]
hzind = [(dx, 5, -1.3), (dx, 6)]
self.mesh = discretize.TensorMesh([hxind, hyind, hzind], "CCC")
# Get index of the center
midx = int(self.mesh.nCx / 2)
midy = int(self.mesh.nCy / 2)
# Lets create a simple Gaussian topo and set the active cells
[xx, yy] = np.meshgrid(self.mesh.vectorNx, self.mesh.vectorNy)
zz = -np.exp((xx**2 + yy**2) / 75**2) + self.mesh.vectorNz[-1]
# Go from topo to actv cells
topo = np.c_[utils.mkvc(xx), utils.mkvc(yy), utils.mkvc(zz)]
actv = utils.surface2ind_topo(self.mesh, topo, "N")
actv = np.where(actv)[0]
# Create active map to go from reduce space to full
self.actvMap = maps.InjectActiveCells(self.mesh, actv, -100)
nC = len(actv)
# Create and array of observation points
xr = np.linspace(-20.0, 20.0, 20)
yr = np.linspace(-20.0, 20.0, 20)
X, Y = np.meshgrid(xr, yr)
# Move the observation points 5m above the topo
Z = -np.exp((X**2 + Y**2) / 75**2) + self.mesh.vectorNz[-1] + 5.0
# Create a MAGsurvey
locXYZ = np.c_[utils.mkvc(X.T), utils.mkvc(Y.T), utils.mkvc(Z.T)]
rxLoc = gravity.Point(locXYZ)
srcField = gravity.SourceField([rxLoc])
survey = gravity.Survey(srcField)
# We can now create a density model and generate data
# Here a simple block in half-space
model = np.zeros((self.mesh.nCx, self.mesh.nCy, self.mesh.nCz))
model[(midx - 2):(midx + 2), (midy - 2):(midy + 2), -6:-2] = 0.5
model = utils.mkvc(model)
self.model = model[actv]
# Create active map to go from reduce set to full
actvMap = maps.InjectActiveCells(self.mesh, actv, ndv)
# Create reduced identity map
idenMap = maps.IdentityMap(nP=nC)
# Create the forward model operator
sim = gravity.Simulation3DIntegral(
self.mesh,
survey=survey,
rhoMap=idenMap,
actInd=actv,
store_sensitivities="ram",
)
# Compute linear forward operator and compute some data
# computing sensitivities to ram is best using dask processes
with dask.config.set(scheduler="processes"):
data = sim.make_synthetic_data(self.model,
relative_error=0.0,
noise_floor=0.001,
add_noise=True)
print(sim.G)
# Create a regularization
reg = regularization.Sparse(self.mesh, indActive=actv, mapping=idenMap)
reg.norms = np.c_[0, 0, 0, 0]
reg.gradientType = "component"
# reg.eps_p, reg.eps_q = 5e-2, 1e-2
# Data misfit function
dmis = data_misfit.L2DataMisfit(simulation=sim, data=data)
# Add directives to the inversion
opt = optimization.ProjectedGNCG(maxIter=100,
lower=-1.0,
upper=1.0,
maxIterLS=20,
maxIterCG=10,
tolCG=1e-3)
invProb = inverse_problem.BaseInvProblem(dmis, reg, opt, beta=1e8)
# Here is where the norms are applied
IRLS = directives.Update_IRLS(f_min_change=1e-4, minGNiter=1)
update_Jacobi = directives.UpdatePreconditioner()
sensitivity_weights = directives.UpdateSensitivityWeights(
everyIter=False)
self.inv = inversion.BaseInversion(
invProb, directiveList=[IRLS, sensitivity_weights, update_Jacobi])
self.sim = sim
def run(plotIt=True):
# Define the inducing field parameter
H0 = (50000, 90, 0)
# Create a mesh
dx = 5.0
hxind = [(dx, 5, -1.3), (dx, 10), (dx, 5, 1.3)]
hyind = [(dx, 5, -1.3), (dx, 10), (dx, 5, 1.3)]
hzind = [(dx, 5, -1.3), (dx, 10)]
mesh = TensorMesh([hxind, hyind, hzind], "CCC")
# Get index of the center
midx = int(mesh.nCx / 2)
midy = int(mesh.nCy / 2)
# Lets create a simple Gaussian topo and set the active cells
[xx, yy] = np.meshgrid(mesh.vectorNx, mesh.vectorNy)
zz = -np.exp((xx**2 + yy**2) / 75**2) + mesh.vectorNz[-1]
# We would usually load a topofile
topo = np.c_[utils.mkvc(xx), utils.mkvc(yy), utils.mkvc(zz)]
# Go from topo to array of indices of active cells
actv = utils.surface2ind_topo(mesh, topo, "N")
actv = np.where(actv)[0]
nC = len(actv)
# Create and array of observation points
xr = np.linspace(-20.0, 20.0, 20)
yr = np.linspace(-20.0, 20.0, 20)
X, Y = np.meshgrid(xr, yr)
# Move the observation points 5m above the topo
Z = -np.exp((X**2 + Y**2) / 75**2) + mesh.vectorNz[-1] + 5.0
# Create a MAGsurvey
rxLoc = np.c_[utils.mkvc(X.T), utils.mkvc(Y.T), utils.mkvc(Z.T)]
rxLoc = magnetics.receivers.Point(rxLoc, components=["tmi"])
srcField = magnetics.sources.SourceField(receiver_list=[rxLoc],
parameters=H0)
survey = magnetics.survey.Survey(srcField)
# We can now create a susceptibility model and generate data
# Here a simple block in half-space
model = np.zeros((mesh.nCx, mesh.nCy, mesh.nCz))
model[(midx - 2):(midx + 2), (midy - 2):(midy + 2), -6:-2] = 0.02
model = utils.mkvc(model)
model = model[actv]
# Create active map to go from reduce set to full
actvMap = maps.InjectActiveCells(mesh, actv, -100)
# Create reduced identity map
idenMap = maps.IdentityMap(nP=nC)
# Create the forward model operator
simulation = magnetics.simulation.Simulation3DIntegral(
survey=survey,
mesh=mesh,
chiMap=idenMap,
actInd=actv,
)
# Compute linear forward operator and compute some data
d = simulation.dpred(model)
# Add noise and uncertainties
# We add some random Gaussian noise (1nT)
synthetic_data = d + np.random.randn(len(d))
wd = np.ones(len(synthetic_data)) * 1.0 # Assign flat uncertainties
data_object = data.Data(survey, dobs=synthetic_data, noise_floor=wd)
# Create a regularization
reg = regularization.Sparse(mesh, indActive=actv, mapping=idenMap)
reg.mref = np.zeros(nC)
reg.norms = np.c_[0, 0, 0, 0]
# reg.eps_p, reg.eps_q = 1e-0, 1e-0
# Create sensitivity weights from our linear forward operator
rxLoc = survey.source_field.receiver_list[0].locations
m0 = np.ones(nC) * 1e-4 # Starting model
# Data misfit function
dmis = data_misfit.L2DataMisfit(simulation=simulation, data=data_object)
dmis.W = 1 / wd
# Add directives to the inversion
opt = optimization.ProjectedGNCG(maxIter=20,
lower=0.0,
upper=1.0,
maxIterLS=20,
maxIterCG=20,
tolCG=1e-3)
invProb = inverse_problem.BaseInvProblem(dmis, reg, opt)
betaest = directives.BetaEstimate_ByEig(beta0_ratio=1e-1)
# Here is where the norms are applied
# Use pick a threshold parameter empirically based on the distribution of
# model parameters
IRLS = directives.Update_IRLS(f_min_change=1e-3, max_irls_iterations=40)
saveDict = directives.SaveOutputEveryIteration(save_txt=False)
update_Jacobi = directives.UpdatePreconditioner()
# Add sensitivity weights
sensitivity_weights = directives.UpdateSensitivityWeights(everyIter=False)
inv = inversion.BaseInversion(
invProb,
directiveList=[
sensitivity_weights, IRLS, betaest, update_Jacobi, saveDict
],
)
# Run the inversion
mrec = inv.run(m0)
if plotIt:
# Here is the recovered susceptibility model
ypanel = midx
zpanel = -5
m_l2 = actvMap * invProb.l2model
m_l2[m_l2 == -100] = np.nan
m_lp = actvMap * mrec
m_lp[m_lp == -100] = np.nan
m_true = actvMap * model
m_true[m_true == -100] = np.nan
# Plot the data
utils.plot_utils.plot2Ddata(rxLoc, d)
plt.figure()
# Plot L2 model
ax = plt.subplot(321)
mesh.plotSlice(
m_l2,
ax=ax,
normal="Z",
ind=zpanel,
grid=True,
clim=(model.min(), model.max()),
)
plt.plot(
([mesh.vectorCCx[0], mesh.vectorCCx[-1]]),
([mesh.vectorCCy[ypanel], mesh.vectorCCy[ypanel]]),
color="w",
)
plt.title("Plan l2-model.")
plt.gca().set_aspect("equal")
plt.ylabel("y")
ax.xaxis.set_visible(False)
plt.gca().set_aspect("equal", adjustable="box")
# Vertica section
ax = plt.subplot(322)
mesh.plotSlice(
m_l2,
ax=ax,
normal="Y",
ind=midx,
grid=True,
clim=(model.min(), model.max()),
)
plt.plot(
([mesh.vectorCCx[0], mesh.vectorCCx[-1]]),
([mesh.vectorCCz[zpanel], mesh.vectorCCz[zpanel]]),
color="w",
)
plt.title("E-W l2-model.")
plt.gca().set_aspect("equal")
ax.xaxis.set_visible(False)
plt.ylabel("z")
plt.gca().set_aspect("equal", adjustable="box")
# Plot Lp model
ax = plt.subplot(323)
mesh.plotSlice(
m_lp,
ax=ax,
normal="Z",
ind=zpanel,
grid=True,
clim=(model.min(), model.max()),
)
plt.plot(
([mesh.vectorCCx[0], mesh.vectorCCx[-1]]),
([mesh.vectorCCy[ypanel], mesh.vectorCCy[ypanel]]),
color="w",
)
plt.title("Plan lp-model.")
plt.gca().set_aspect("equal")
ax.xaxis.set_visible(False)
plt.ylabel("y")
plt.gca().set_aspect("equal", adjustable="box")
# Vertical section
ax = plt.subplot(324)
mesh.plotSlice(
m_lp,
ax=ax,
normal="Y",
ind=midx,
grid=True,
clim=(model.min(), model.max()),
)
plt.plot(
([mesh.vectorCCx[0], mesh.vectorCCx[-1]]),
([mesh.vectorCCz[zpanel], mesh.vectorCCz[zpanel]]),
color="w",
)
plt.title("E-W lp-model.")
plt.gca().set_aspect("equal")
ax.xaxis.set_visible(False)
plt.ylabel("z")
plt.gca().set_aspect("equal", adjustable="box")
# Plot True model
ax = plt.subplot(325)
mesh.plotSlice(
m_true,
ax=ax,
normal="Z",
ind=zpanel,
grid=True,
clim=(model.min(), model.max()),
)
plt.plot(
([mesh.vectorCCx[0], mesh.vectorCCx[-1]]),
([mesh.vectorCCy[ypanel], mesh.vectorCCy[ypanel]]),
color="w",
)
plt.title("Plan true model.")
plt.gca().set_aspect("equal")
plt.xlabel("x")
plt.ylabel("y")
plt.gca().set_aspect("equal", adjustable="box")
# Vertical section
ax = plt.subplot(326)
mesh.plotSlice(
m_true,
ax=ax,
normal="Y",
ind=midx,
grid=True,
clim=(model.min(), model.max()),
)
plt.plot(
([mesh.vectorCCx[0], mesh.vectorCCx[-1]]),
([mesh.vectorCCz[zpanel], mesh.vectorCCz[zpanel]]),
color="w",
)
plt.title("E-W true model.")
plt.gca().set_aspect("equal")
plt.xlabel("x")
plt.ylabel("z")
plt.gca().set_aspect("equal", adjustable="box")
# Plot convergence curves
fig, axs = plt.figure(), plt.subplot()
axs.plot(saveDict.phi_d, "k", lw=2)
axs.plot(
np.r_[IRLS.iterStart, IRLS.iterStart],
np.r_[0, np.max(saveDict.phi_d)],
"k:",
)
twin = axs.twinx()
twin.plot(saveDict.phi_m, "k--", lw=2)
axs.text(
IRLS.iterStart,
0,
"IRLS Steps",
va="bottom",
ha="center",
rotation="vertical",
size=12,
bbox={"facecolor": "white"},
)
axs.set_ylabel("$\phi_d$", size=16, rotation=0)
axs.set_xlabel("Iterations", size=14)
twin.set_ylabel("$\phi_m$", size=16, rotation=0)
frequencies = [1.0] # Frequency (Hz)
omegas = [2.0 * np.pi] # Radial frequency (Hz)
survey = utils.define_survey(frequencies, receiver_locations, source_locations,
ntx)
# Refine at certain locations
M.refine_at_locations(mesh, source_locations)
M.refine_at_locations(mesh, receiver_locations)
mesh.finalize()
# Resistivity in Ohm m
res_background = 1.0
res_block = 100.0
# Find cells that are active in the forward modeling (cells below surface)
ind_active = surface2ind_topo(mesh, surface)
# Define mapping from model to active cells
model_map = maps.InjectActiveCells(mesh, ind_active, res_background)
# Define model. Models in SimPEG are vector arrays
model = res_background * np.ones(ind_active.sum())
ind_block = utils.get_ind_block(mesh, ind_active, box_coordinates)
model[ind_block] = res_block
# Run the adaptive meshing algorithm
mesh, ex, ey, ez, diff_list = iterator(mesh,
domain,
surface,
cell_width,
box_surface,
def run(
plotIt=True,
survey_type="dipole-dipole",
rho_background=1e3,
rho_block=1e2,
block_x0=100,
block_dx=10,
block_y0=-10,
block_dy=5,
):
np.random.seed(1)
# Initiate I/O class for DC
IO = DC.IO()
# Obtain ABMN locations
xmin, xmax = 0.0, 200.0
ymin, ymax = 0.0, 0.0
zmin, zmax = 0, 0
endl = np.array([[xmin, ymin, zmin], [xmax, ymax, zmax]])
# Generate DC survey object
survey = DCutils.gen_DCIPsurvey(endl,
survey_type=survey_type,
dim=2,
a=10,
b=10,
n=10)
survey = IO.from_ambn_locations_to_survey(
survey.locations_a,
survey.locations_b,
survey.locations_m,
survey.locations_n,
survey_type,
data_dc_type="volt",
)
# Obtain 2D TensorMesh
mesh, actind = IO.set_mesh()
# Flat topography
actind = utils.surface2ind_topo(
mesh, np.c_[mesh.vectorCCx, mesh.vectorCCx * 0.0])
survey.drape_electrodes_on_topography(mesh, actind, option="top")
# Use Exponential Map: m = log(rho)
actmap = maps.InjectActiveCells(mesh,
indActive=actind,
valInactive=np.log(1e8))
parametric_block = maps.ParametricBlock(mesh, slopeFact=1e2)
mapping = maps.ExpMap(mesh) * parametric_block
# Set true model
# val_background,val_block, block_x0, block_dx, block_y0, block_dy
mtrue = np.r_[np.log(1e3), np.log(10), 100, 10, -20, 10]
# Set initial model
m0 = np.r_[np.log(rho_background),
np.log(rho_block), block_x0, block_dx, block_y0, block_dy, ]
rho = mapping * mtrue
rho0 = mapping * m0
# Show the true conductivity model
fig = plt.figure(figsize=(12, 3))
ax = plt.subplot(111)
temp = rho.copy()
temp[~actind] = np.nan
out = mesh.plotImage(
temp,
grid=False,
ax=ax,
gridOpts={"alpha": 0.2},
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
)
ax.plot(survey.electrode_locations[:, 0], survey.electrode_locations[:, 1],
"k.")
ax.set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
ax.set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
cb = plt.colorbar(out[0])
cb.set_label("Resistivity (ohm-m)")
ax.set_aspect("equal")
ax.set_title("True resistivity model")
plt.show()
# Show the true conductivity model
fig = plt.figure(figsize=(12, 3))
ax = plt.subplot(111)
temp = rho0.copy()
temp[~actind] = np.nan
out = mesh.plotImage(
temp,
grid=False,
ax=ax,
gridOpts={"alpha": 0.2},
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
)
ax.plot(survey.electrode_locations[:, 0], survey.electrode_locations[:, 1],
"k.")
ax.set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
ax.set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
cb = plt.colorbar(out[0])
cb.set_label("Resistivity (ohm-m)")
ax.set_aspect("equal")
ax.set_title("Initial resistivity model")
plt.show()
# Generate 2.5D DC problem
# "N" means potential is defined at nodes
prb = DC.Simulation2DNodal(mesh,
survey=survey,
rhoMap=mapping,
storeJ=True,
solver=Solver)
# Make synthetic DC data with 5% Gaussian noise
data = prb.make_synthetic_data(mtrue, relative_error=0.05, add_noise=True)
# Show apparent resisitivty pseudo-section
IO.plotPseudoSection(data=data.dobs / IO.G,
data_type="apparent_resistivity")
# Show apparent resisitivty histogram
fig = plt.figure()
out = hist(data.dobs / IO.G, bins=20)
plt.show()
# Set standard_deviation
# floor
eps = 10**(-3.2)
# percentage
relative = 0.05
dmisfit = data_misfit.L2DataMisfit(simulation=prb, data=data)
uncert = abs(data.dobs) * relative + eps
dmisfit.standard_deviation = uncert
# Map for a regularization
mesh_1d = discretize.TensorMesh([parametric_block.nP])
# Related to inversion
reg = regularization.Simple(mesh_1d, alpha_x=0.0)
opt = optimization.InexactGaussNewton(maxIter=10)
invProb = inverse_problem.BaseInvProblem(dmisfit, reg, opt)
beta = directives.BetaSchedule(coolingFactor=5, coolingRate=2)
betaest = directives.BetaEstimate_ByEig(beta0_ratio=1e0)
target = directives.TargetMisfit()
updateSensW = directives.UpdateSensitivityWeights()
update_Jacobi = directives.UpdatePreconditioner()
invProb.beta = 0.0
inv = inversion.BaseInversion(invProb, directiveList=[target])
prb.counter = opt.counter = utils.Counter()
opt.LSshorten = 0.5
opt.remember("xc")
# Run inversion
mopt = inv.run(m0)
# Convert obtained inversion model to resistivity
# rho = M(m), where M(.) is a mapping
rho_est = mapping * mopt
rho_true = rho.copy()
# show recovered conductivity
vmin, vmax = rho.min(), rho.max()
fig, ax = plt.subplots(2, 1, figsize=(20, 6))
out1 = mesh.plotImage(
rho_true,
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
ax=ax[0],
)
out2 = mesh.plotImage(
rho_est,
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
ax=ax[1],
)
out = [out1, out2]
for i in range(2):
ax[i].plot(survey.electrode_locations[:, 0],
survey.electrode_locations[:, 1], "kv")
ax[i].set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
ax[i].set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
cb = plt.colorbar(out[i][0], ax=ax[i])
cb.set_label("Resistivity ($\Omega$m)")
ax[i].set_xlabel("Northing (m)")
ax[i].set_ylabel("Elevation (m)")
ax[i].set_aspect("equal")
ax[0].set_title("True resistivity model")
ax[1].set_title("Recovered resistivity model")
plt.tight_layout()
plt.show()
mesh.finalize() ############################################################### # Project Surveys to Discretized Topography # ----------------------------------------- # # It is important that electrodes are not model as being in the air. Even if the # electrodes are properly located along surface topography, they may lie above # the discretized topography. This step is carried out to ensure all electrodes # like on the discretized surface. # # Find cells that lie below surface topography ind_active = surface2ind_topo(mesh, topo_xyz[:, [0, 2]]) # Shift electrodes to the surface of discretized topography survey.drape_electrodes_on_topography(mesh, ind_active, option="top") ######################################################## # Starting/Reference Model and Mapping on OcTree Mesh # --------------------------------------------------- # # Here, we would create starting and/or reference models for the DC inversion as # well as the mapping from the model space to the active cells. Starting and # reference models can be a constant background value or contain a-priori # structures. Here, the starting model is the natural log of 0.01 S/m. # # Define conductivity model in S/m (or resistivity model in Ohm m)
def run(plotIt=True, survey_type="dipole-dipole"):
np.random.seed(1)
# Initiate I/O class for DC
IO = DC.IO()
# Obtain ABMN locations
xmin, xmax = 0.0, 200.0
ymin, ymax = 0.0, 0.0
zmin, zmax = 0, 0
endl = np.array([[xmin, ymin, zmin], [xmax, ymax, zmax]])
# Generate DC survey object
survey_dc = gen_DCIPsurvey(endl,
survey_type=survey_type,
dim=2,
a=10,
b=10,
n=10)
survey_dc = IO.from_abmn_locations_to_survey(
survey_dc.locations_a,
survey_dc.locations_b,
survey_dc.locations_m,
survey_dc.locations_n,
survey_type,
data_dc_type="volt",
data_ip_type="volt",
)
# Obtain 2D TensorMesh
mesh, actind = IO.set_mesh()
topo, mesh1D = genTopography(mesh, -10, 0, its=100)
actind = utils.surface2ind_topo(mesh, np.c_[mesh1D.vectorCCx, topo])
survey_dc.drape_electrodes_on_topography(mesh, actind, option="top")
# Build conductivity and chargeability model
blk_inds_c = utils.model_builder.getIndicesSphere(np.r_[60.0, -25.0], 12.5,
mesh.gridCC)
blk_inds_r = utils.model_builder.getIndicesSphere(np.r_[140.0, -25.0],
12.5, mesh.gridCC)
blk_inds_charg = utils.model_builder.getIndicesSphere(
np.r_[100.0, -25], 12.5, mesh.gridCC)
sigma = np.ones(mesh.nC) * 1.0 / 100.0
sigma[blk_inds_c] = 1.0 / 10.0
sigma[blk_inds_r] = 1.0 / 1000.0
sigma[~actind] = 1.0 / 1e8
rho = 1.0 / sigma
charg = np.zeros(mesh.nC)
charg[blk_inds_charg] = 0.1
# Show the true conductivity model
if plotIt:
fig, axs = plt.subplots(2, 1, figsize=(12, 6))
temp_rho = rho.copy()
temp_rho[~actind] = np.nan
temp_charg = charg.copy()
temp_charg[~actind] = np.nan
out1 = mesh.plotImage(
temp_rho,
grid=True,
ax=axs[0],
gridOpts={"alpha": 0.2},
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
)
out2 = mesh.plotImage(
temp_charg,
grid=True,
ax=axs[1],
gridOpts={"alpha": 0.2},
clim=(0, 0.1),
pcolorOpts={"cmap": "magma"},
)
for i in range(2):
axs[i].plot(
survey_dc.electrode_locations[:, 0],
survey_dc.electrode_locations[:, 1],
"kv",
)
axs[i].set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
axs[i].set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
axs[i].set_aspect("equal")
cb = plt.colorbar(out1[0], ax=axs[0])
cb.set_label("Resistivity (ohm-m)")
cb = plt.colorbar(out2[0], ax=axs[1])
cb.set_label("Chargeability")
plt.show()
# Use Exponential Map: m = log(rho)
actmap = maps.InjectActiveCells(mesh,
indActive=actind,
valInactive=np.log(1e8))
mapping = maps.ExpMap(mesh) * actmap
# Generate mtrue_dc for resistivity
mtrue_dc = np.log(rho[actind])
# Generate 2.5D DC problem
# "N" means potential is defined at nodes
prb = DC.Simulation2DNodal(mesh,
survey=survey_dc,
rhoMap=mapping,
storeJ=True,
solver=Solver)
# Make synthetic DC data with 5% Gaussian noise
data_dc = prb.make_synthetic_data(mtrue_dc,
relative_error=0.05,
add_noise=True)
IO.data_dc = data_dc.dobs
# Generate mtrue_ip for chargability
mtrue_ip = charg[actind]
# Generate 2.5D DC problem
# "N" means potential is defined at nodes
survey_ip = IP.from_dc_to_ip_survey(survey_dc, dim="2.5D")
prb_ip = IP.Simulation2DNodal(mesh,
survey=survey_ip,
etaMap=actmap,
storeJ=True,
rho=rho,
solver=Solver)
data_ip = prb_ip.make_synthetic_data(mtrue_ip,
relative_error=0.05,
add_noise=True)
IO.data_ip = data_ip.dobs
# Show apparent resisitivty pseudo-section
if plotIt:
IO.plotPseudoSection(data_type="apparent_resistivity",
scale="log",
cmap="viridis")
plt.show()
# Show apparent chargeability pseudo-section
if plotIt:
IO.plotPseudoSection(data_type="apparent_chargeability",
scale="linear",
cmap="magma")
plt.show()
# Show apparent resisitivty histogram
if plotIt:
fig = plt.figure(figsize=(10, 4))
ax1 = plt.subplot(121)
out = hist(np.log10(abs(IO.voltages)), bins=20)
ax1.set_xlabel("log10 DC voltage (V)")
ax2 = plt.subplot(122)
out = hist(IO.apparent_resistivity, bins=20)
ax2.set_xlabel("Apparent Resistivity ($\Omega$m)")
plt.tight_layout()
plt.show()
# Set initial model based upon histogram
m0_dc = np.ones(actmap.nP) * np.log(100.0)
# Set standard deviation
# floor
data_dc.noise_floor = 10**(-3.2)
# percentage
data_dc.relative_error = 0.05
mopt_dc, pred_dc = DC.run_inversion(m0_dc,
prb,
data_dc,
actind,
mesh,
beta0_ratio=1e0,
use_sensitivity_weight=True)
# Convert obtained inversion model to resistivity
# rho = M(m), where M(.) is a mapping
rho_est = mapping * mopt_dc
rho_est[~actind] = np.nan
rho_true = rho.copy()
rho_true[~actind] = np.nan
# show recovered conductivity
if plotIt:
vmin, vmax = rho.min(), rho.max()
fig, ax = plt.subplots(2, 1, figsize=(20, 6))
out1 = mesh.plotImage(
rho_true,
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
ax=ax[0],
)
out2 = mesh.plotImage(
rho_est,
clim=(10, 1000),
pcolorOpts={
"cmap": "viridis",
"norm": colors.LogNorm()
},
ax=ax[1],
)
out = [out1, out2]
for i in range(2):
ax[i].plot(
survey_dc.electrode_locations[:, 0],
survey_dc.electrode_locations[:, 1],
"kv",
)
ax[i].set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
ax[i].set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
cb = plt.colorbar(out[i][0], ax=ax[i])
cb.set_label("Resistivity ($\Omega$m)")
ax[i].set_xlabel("Northing (m)")
ax[i].set_ylabel("Elevation (m)")
ax[i].set_aspect("equal")
plt.tight_layout()
plt.show()
# Show apparent resisitivty histogram
if plotIt:
fig = plt.figure(figsize=(10, 4))
ax1 = plt.subplot(121)
out = hist(np.log10(abs(IO.voltages_ip)), bins=20)
ax1.set_xlabel("log10 IP voltage (V)")
ax2 = plt.subplot(122)
out = hist(IO.apparent_chargeability, bins=20)
ax2.set_xlabel("Apparent Chargeability (V/V)")
plt.tight_layout()
plt.show()
# Set initial model based upon histogram
m0_ip = np.ones(actmap.nP) * 1e-10
# Set standard deviation
# floor
data_ip.noise_floor = 10**(-4)
# percentage
data_ip.relative_error = 0.05
# Clean sensitivity function formed with true resistivity
prb_ip._Jmatrix = None
# Input obtained resistivity to form sensitivity
prb_ip.rho = mapping * mopt_dc
mopt_ip, _ = IP.run_inversion(
m0_ip,
prb_ip,
data_ip,
actind,
mesh,
upper=np.Inf,
lower=0.0,
beta0_ratio=1e0,
use_sensitivity_weight=True,
)
# Convert obtained inversion model to chargeability
# charg = M(m), where M(.) is a mapping for cells below topography
charg_est = actmap * mopt_ip
charg_est[~actind] = np.nan
charg_true = charg.copy()
charg_true[~actind] = np.nan
# show recovered chargeability
if plotIt:
fig, ax = plt.subplots(2, 1, figsize=(20, 6))
out1 = mesh.plotImage(charg_true,
clim=(0, 0.1),
pcolorOpts={"cmap": "magma"},
ax=ax[0])
out2 = mesh.plotImage(charg_est,
clim=(0, 0.1),
pcolorOpts={"cmap": "magma"},
ax=ax[1])
out = [out1, out2]
for i in range(2):
ax[i].plot(
survey_dc.electrode_locations[:, 0],
survey_dc.electrode_locations[:, 1],
"rv",
)
ax[i].set_xlim(IO.grids[:, 0].min(), IO.grids[:, 0].max())
ax[i].set_ylim(-IO.grids[:, 1].max(), IO.grids[:, 1].min())
cb = plt.colorbar(out[i][0], ax=ax[i])
cb.set_label("Resistivity ($\Omega$m)")
ax[i].set_xlabel("Northing (m)")
ax[i].set_ylabel("Elevation (m)")
ax[i].set_aspect("equal")
plt.tight_layout()
plt.show()
# Starting/Reference Model and Mapping on Tensor Mesh
# ---------------------------------------------------
#
# Here, we create starting and/or reference models for the inversion as
# well as the mapping from the model space to the active cells. Starting and
# reference models can be a constant background value or contain a-priori
# structures. Here, the background is 1e-6 g/cc.
#
# Define density contrast values for each unit in g/cc. Don't make this 0!
# Otherwise the gradient for the 1st iteration is zero and the inversion will
# not converge.
background_density = 1e-6
# Find the indecies of the active cells in forward model (ones below surface)
ind_active = surface2ind_topo(mesh, xyz_topo)
# Define mapping from model to active cells
nC = int(ind_active.sum())
model_map = maps.IdentityMap(
nP=nC) # model consists of a value for each active cell
# Define and plot starting model
starting_model = background_density * np.ones(nC)
##############################################
# Define the Physics
# ------------------
#
# Here, we define the physics of the gravity problem by using the simulation
# class.
mesh = refine_box(mesh)
mesh.finalize()
background_value = 100.0
dyke_value = 40.0
block_value = 70.0
# Define surface topography as an (N, 3) np.array. You could also load a file
# containing the xyz points
[xx, yy] = np.meshgrid(mesh.vectorNx, mesh.vectorNy)
zz = -3 * np.exp((xx**2 + yy**2) / 60**2) + 45.0
topo = np.c_[mkvc(xx), mkvc(yy), mkvc(zz)]
# Find cells below topography and define mapping
air_value = 0.0
ind_active = surface2ind_topo(mesh, topo)
model_map = maps.InjectActiveCells(mesh, ind_active, air_value)
# Define the model on subsurface cells
model = background_value * np.ones(ind_active.sum())
ind_dyke = (mesh.gridCC[ind_active, 0] > 20.0) & (mesh.gridCC[ind_active, 0] <
40.0)
model[ind_dyke] = dyke_value
ind_block = ((mesh.gridCC[ind_active, 0] > -40.0)
& (mesh.gridCC[ind_active, 0] < -10.0)
& (mesh.gridCC[ind_active, 1] > -30.0)
& (mesh.gridCC[ind_active, 1] < 30.0)
& (mesh.gridCC[ind_active, 2] > -40.0)
& (mesh.gridCC[ind_active, 2] < 0.0))
model[ind_block] = block_value
"colors": "k",
"linewidths": 2,
"linestyles": "--"
},
method="nearest",
)
plt.subplots_adjust(hspace=-0.25, wspace=0.1)
plt.show()
# Load Topo
topo_file = io_utils.download(
"https://storage.googleapis.com/simpeg/pgi_tutorial_assets/CDED_Lake_warp.xyz"
)
topo = np.genfromtxt(topo_file, skip_header=1)
# find the active cells
actv = utils.surface2ind_topo(mesh, topo, gridLoc="CC")
# Create active map to go from reduce set to full
ndv = np.nan
actvMap = maps.InjectActiveCells(mesh, actv, ndv)
nactv = int(actv.sum())
# Create simulations and data misfits
# Wires mapping
wires = maps.Wires(("den", actvMap.nP), ("sus", actvMap.nP))
gravmap = actvMap * wires.den
magmap = actvMap * wires.sus
idenMap = maps.IdentityMap(nP=nactv)
# Grav problem
simulation_grav = pf.gravity.simulation.Simulation3DIntegral(
survey=data_grav.survey,
mesh=mesh,
def run(plotIt=True):
H0 = (50000.0, 90.0, 0.0)
# Create a mesh
dx = 5.0
hxind = [(dx, 5, -1.3), (dx, 10), (dx, 5, 1.3)]
hyind = [(dx, 5, -1.3), (dx, 10), (dx, 5, 1.3)]
hzind = [(dx, 5, -1.3), (dx, 10)]
mesh = discretize.TensorMesh([hxind, hyind, hzind], "CCC")
# Lets create a simple Gaussian topo and set the active cells
[xx, yy] = np.meshgrid(mesh.vectorNx, mesh.vectorNy)
zz = -np.exp((xx ** 2 + yy ** 2) / 75 ** 2) + mesh.vectorNz[-1]
# We would usually load a topofile
topo = np.c_[utils.mkvc(xx), utils.mkvc(yy), utils.mkvc(zz)]
# Go from topo to array of indices of active cells
actv = utils.surface2ind_topo(mesh, topo, "N")
actv = np.where(actv)[0]
# Create and array of observation points
xr = np.linspace(-20.0, 20.0, 20)
yr = np.linspace(-20.0, 20.0, 20)
X, Y = np.meshgrid(xr, yr)
# Move the observation points 5m above the topo
Z = -np.exp((X ** 2 + Y ** 2) / 75 ** 2) + mesh.vectorNz[-1] + 5.0
# Create a MAGsurvey
rxLoc = np.c_[utils.mkvc(X.T), utils.mkvc(Y.T), utils.mkvc(Z.T)]
rxLoc = magnetics.Point(rxLoc)
srcField = magnetics.SourceField([rxLoc], parameters=H0)
survey = magnetics.Survey(srcField)
# We can now create a susceptibility model and generate data
model = np.zeros(mesh.nC)
# Change values in half the domain
model[mesh.gridCC[:, 0] < 0] = 0.01
# Add a block in half-space
model = utils.model_builder.addBlock(
mesh.gridCC, model, np.r_[-10, -10, 20], np.r_[10, 10, 40], 0.05
)
model = utils.mkvc(model)
model = model[actv]
# Create active map to go from reduce set to full
actvMap = maps.InjectActiveCells(mesh, actv, np.nan)
# Create reduced identity map
idenMap = maps.IdentityMap(nP=len(actv))
# Create the forward model operator
prob = magnetics.Simulation3DIntegral(
mesh,
survey=survey,
chiMap=idenMap,
actInd=actv,
store_sensitivities="forward_only",
)
# Compute linear forward operator and compute some data
data = prob.make_synthetic_data(
model, relative_error=0.0, noise_floor=1, add_noise=True
)
# Create a homogenous maps for the two domains
domains = [mesh.gridCC[actv, 0] < 0, mesh.gridCC[actv, 0] >= 0]
homogMap = maps.SurjectUnits(domains)
# Create a wire map for a second model space, voxel based
wires = maps.Wires(("h**o", len(domains)), ("hetero", len(actv)))
# Create Sum map
sumMap = maps.SumMap([homogMap * wires.h**o, wires.hetero])
# Create the forward model operator
prob = magnetics.Simulation3DIntegral(
mesh, survey=survey, chiMap=sumMap, actInd=actv, store_sensitivities="ram"
)
# Make depth weighting
wr = np.zeros(sumMap.shape[1])
print(prob.nC)
# print(prob.M.shape) # why does this reset nC
G = prob.G
# Take the cell number out of the scaling.
# Want to keep high sens for large volumes
scale = utils.sdiag(
np.r_[utils.mkvc(1.0 / homogMap.P.sum(axis=0)), np.ones_like(actv)]
)
for ii in range(survey.nD):
wr += (
(prob.G[ii, :] * prob.chiMap.deriv(np.ones(sumMap.shape[1]) * 1e-4) * scale)
/ data.standard_deviation[ii]
) ** 2.0
# Scale the model spaces independently
wr[wires.h**o.index] /= np.max((wires.h**o * wr))
wr[wires.hetero.index] /= np.max(wires.hetero * wr)
wr = wr ** 0.5
## Create a regularization
# For the homogeneous model
regMesh = discretize.TensorMesh([len(domains)])
reg_m1 = regularization.Sparse(regMesh, mapping=wires.h**o)
reg_m1.cell_weights = wires.h**o * wr
reg_m1.norms = np.c_[0, 2, 2, 2]
reg_m1.mref = np.zeros(sumMap.shape[1])
# Regularization for the voxel model
reg_m2 = regularization.Sparse(mesh, indActive=actv, mapping=wires.hetero)
reg_m2.cell_weights = wires.hetero * wr
reg_m2.norms = np.c_[0, 1, 1, 1]
reg_m2.mref = np.zeros(sumMap.shape[1])
reg = reg_m1 + reg_m2
# Data misfit function
dmis = data_misfit.L2DataMisfit(simulation=prob, data=data)
# Add directives to the inversion
opt = optimization.ProjectedGNCG(
maxIter=100,
lower=0.0,
upper=1.0,
maxIterLS=20,
maxIterCG=10,
tolCG=1e-3,
tolG=1e-3,
eps=1e-6,
)
invProb = inverse_problem.BaseInvProblem(dmis, reg, opt)
betaest = directives.BetaEstimate_ByEig()
# Here is where the norms are applied
# Use pick a threshold parameter empirically based on the distribution of
# model parameters
IRLS = directives.Update_IRLS(f_min_change=1e-3, minGNiter=1)
update_Jacobi = directives.UpdatePreconditioner()
inv = inversion.BaseInversion(invProb, directiveList=[IRLS, betaest, update_Jacobi])
# Run the inversion
m0 = np.ones(sumMap.shape[1]) * 1e-4 # Starting model
prob.model = m0
mrecSum = inv.run(m0)
if plotIt:
mesh.plot_3d_slicer(
actvMap * model,
aspect="equal",
zslice=30,
pcolorOpts={"cmap": "inferno_r"},
transparent="slider",
)
mesh.plot_3d_slicer(
actvMap * sumMap * mrecSum,
aspect="equal",
zslice=30,
pcolorOpts={"cmap": "inferno_r"},
transparent="slider",
)
