def calculate_local_north_and_up_in_celestial_coords(self, force_update):
current_time = self.get_time_in_millis()
diff = math.fabs(current_time - self.celestial_coords_last_updated)
if (not force_update) and diff < self.MINIMUM_TIME_BETWEEN_CELESTIAL_COORD_UPDATES_MILLIS:
return
self.celestial_coords_last_updated = current_time
self.update_magnetic_correction()
up_ra, up_dec = Geometry.calculate_RADec_of_zenith(self.get_time(), self.location)
self.up_celestial = get_instance(up_ra, up_dec)
z = self.AXIS_OF_EARTHS_ROTATION
z_dotu = Geometry.scalar_product(self.up_celestial, z)
self.true_north_celestial = \
Geometry.add_vectors(z, Geometry.scale_vector(self.up_celestial, -z_dotu))
self.true_north_celestial.normalize()
self.true_east_celestial = Geometry.vector_product(self.true_north_celestial, \
self.up_celestial)
# Apply magnetic correction. Rather than correct the phone's axes for
# the magnetic declination, it's more efficient to rotate the
# celestial axes by the same amount in the opposite direction.
declination = self.magnetic_declination_calc.get_declination()
rotation_matrix = Geometry.calculate_rotation_matrix(declination, self.up_celestial)
magnetic_north_celestial = Geometry.matrix_vector_multiply(rotation_matrix, \
self.true_north_celestial)
magnetic_east_celestial = Geometry.vector_product(magnetic_north_celestial, \
self.up_celestial)
self.axes_magnetic_celestial_matrix = get_colmatrix_from_vectors(magnetic_north_celestial, \
self.up_celestial, \
magnetic_east_celestial)
def calculate_local_north_and_up_in_phone_coords(self):
down = self.acceleration.copy()
down.normalize()
# Magnetic field goes *from* North to South, so reverse it.
magnetic_field_to_north = self.magnetic_field.copy()
magnetic_field_to_north.scale(-1)
magnetic_field_to_north.normalize()
# This is the vector to magnetic North *along the ground*.
v2 = Geometry.scale_vector(down, -Geometry.scalar_product(magnetic_field_to_north, \
down))
magnetic_north_phone = Geometry.add_vectors(magnetic_field_to_north, v2)
magnetic_north_phone.normalize()
up_phone = Geometry.scale_vector(down, -1)
magnetic_east_phone = Geometry.vector_product(magnetic_north_phone, up_phone)
# The matrix is orthogonal, so transpose it to find its inverse.
# Easiest way to do that is to construct it from row vectors instead
# of column vectors.
self.axes_phone_inverse_matrix = \
get_rowmatrix_from_vectors(magnetic_north_phone,
up_phone,
magnetic_east_phone)
