def _igrf_tracefield_hemis(dn, lat, lon, alt, target_ht, step):
import numpy as np
import coord
from numpy import array as arr
lat = float(lat)
lon = float(lon)
alt = float(alt)
target_ht = float(target_ht)
step = float(step)
target_ht = target_ht*1e3
step = step*1e3
lla = np.array([lat, lon, alt*1e3])
lla_field = lla
""" Step 1: trace the field along a given direction """
TOLERANCE = 10 # [m]
i = 0
while (lla[2] > target_ht):
# convert to ECEF:
ecef = coord.lla2ecef(lla)
# Grab field line information:
p = Point(dn, lla[0], lla[1], lla[2]/1e3)
p.run_igrf()
# coordinates follow pyglow's convention:
# (x -> east, y -> north, z -> up)
N = p.By # North
E = p.Bx # East
D = -p.Bz # Down
A = p.B # Total
# Step along the field line
ecef_new = ecef + coord.ven2ecef(lla,[(-D/A*step), (E/A*step), (N/A*step)] )
# Convert to lla coordinates:
lla = coord.ecef2lla(ecef_new)
# add the field line to our collection:
lla_field = np.vstack( [lla_field, lla] )
i = i + 1
""" Step 2: Make the last point close to target_ht """
while (abs(lla[2]-target_ht) > TOLERANCE):
my_error = lla[2]-target_ht
old_step = step
# find out how much we need to step by:
step = -np.sign(step)*abs(lla[2]-target_ht)
ecef = coord.lla2ecef(lla)
p = Point(dn, lla[0], lla[1], lla[2]/1e3)
p.run_igrf()
N = p.Bx # North
E = p.By # East
D = p.Bz # Down
A = p.B # Total
# trace the field, but use the modified step:
ecef_new = ecef + coord.ven2ecef(lla,np.array([(-D/A), (E/A), N/A])*step/(-D/A) )
# TODO : I changed this, is this correct?
lla = coord.ecef2lla(ecef_new)
# replace last entry with the point close to target_ht:
lla_field[-1,:] = lla
return lla_field
def _igrf_tracefield_hemis(dn, lat, lon, alt, target_ht, step):
"""
Helper function to trace along a magnetic field line using IGRF
for only one hemisphere
:param dn: datetime.datetime object of requested trace
:param lat: Latitude [degrees]
:param lon: Longitude [degrees]
:param alt: Altitude [km]
:param target_ht: Altitude to stop trace [km]
:param step: Step size of trace [km]
:return lla: (latitude, longitude, altitude) data structure of trace
with dimentions [Nsteps x 3]
"""
lat = float(lat)
lon = float(lon)
alt = float(alt)
target_ht = float(target_ht)
step = float(step)
target_ht = target_ht * 1e3
step = step * 1e3
lla = np.array([lat, lon, alt * 1e3])
lla_field = lla
""" Step 1: trace the field along a given direction """
TOLERANCE = 10 # [m]
i = 0
while (lla[2] > target_ht):
# convert to ECEF:
ecef = coord.lla2ecef(lla)
# Grab field line information:
p = Point(dn, lla[0], lla[1], lla[2] / 1e3)
p.run_igrf()
# coordinates follow pyglow's convention:
# (x -> east, y -> north, z -> up)
N = p.By # North
E = p.Bx # East
D = -p.Bz # Down
A = p.B # Total
# Step along the field line
ecef_new = ecef + coord.ven2ecef(
lla,
[-D / A * step, E / A * step, N / A * step],
)
# Convert to lla coordinates:
lla = coord.ecef2lla(ecef_new)
# add the field line to our collection:
lla_field = np.vstack([lla_field, lla])
i = i + 1
""" Step 2: Make the last point close to target_ht """
while (abs(lla[2] - target_ht) > TOLERANCE):
my_error = lla[2] - target_ht
old_step = step
# Find out how much we need to step by:
step = -np.sign(step) * abs(lla[2] - target_ht)
ecef = coord.lla2ecef(lla)
p = Point(dn, lla[0], lla[1], lla[2] / 1e3)
p.run_igrf()
N = p.Bx # North
E = p.By # East
D = p.Bz # Down
A = p.B # Total
# Trace the field, but use the modified step:
ecef_new = ecef + coord.ven2ecef(
lla,
np.array([-D / A, E / A, N / A]) * step / (-D / A),
)
# TODO : I changed this, is this correct?
lla = coord.ecef2lla(ecef_new)
# replace last entry with the point close to target_ht:
lla_field[-1, :] = lla
return lla_field
def _igrf_tracefield_hemis(dn, lat, lon, alt, target_ht, step):
import numpy as np
import coord
from numpy import array as arr
lat = float(lat)
lon = float(lon)
alt = float(alt)
target_ht = float(target_ht)
step = float(step)
target_ht = target_ht * 1e3
step = step * 1e3
lla = np.array([lat, lon, alt * 1e3])
lla_field = lla
""" Step 1: trace the field along a given direction """
TOLERANCE = 10 # [m]
i = 0
while (lla[2] > target_ht):
# convert to ECEF:
ecef = coord.lla2ecef(lla)
# Grab field line information:
p = Point(dn, lla[0], lla[1], lla[2] / 1e3)
p.run_igrf()
# coordinates follow pyglow's convention:
# (x -> east, y -> north, z -> up)
N = p.By # North
E = p.Bx # East
D = -p.Bz # Down
A = p.B # Total
# Step along the field line
ecef_new = ecef + coord.ven2ecef(lla, [(-D / A * step), (E / A * step),
(N / A * step)])
# Convert to lla coordinates:
lla = coord.ecef2lla(ecef_new)
# add the field line to our collection:
lla_field = np.vstack([lla_field, lla])
i = i + 1
""" Step 2: Make the last point close to target_ht """
while (abs(lla[2] - target_ht) > TOLERANCE):
my_error = lla[2] - target_ht
old_step = step
# find out how much we need to step by:
step = -np.sign(step) * abs(lla[2] - target_ht)
ecef = coord.lla2ecef(lla)
p = Point(dn, lla[0], lla[1], lla[2] / 1e3)
p.run_igrf()
N = p.Bx # North
E = p.By # East
D = p.Bz # Down
A = p.B # Total
# trace the field, but use the modified step:
ecef_new = ecef + coord.ven2ecef(
lla,
np.array([(-D / A), (E / A), N / A]) * step / (-D / A))
# TODO : I changed this, is this correct?
lla = coord.ecef2lla(ecef_new)
# replace last entry with the point close to target_ht:
lla_field[-1, :] = lla
return lla_field