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Use numpy functions to convert angles between degrees and radians #7

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Oct 12, 2022
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Use numpy functions to convert angles between degrees and radians #7

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37 changes: 22 additions & 15 deletions src/ppigrf/ppigrf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,6 @@
import numpy as np
import pandas as pd
import os
d2r = np.pi/180

basepath = os.path.dirname(__file__)
shc_fn = basepath + '/IGRF13.shc' # Default shc file
Expand Down Expand Up @@ -171,11 +170,12 @@ def get_legendre(theta, keys):
nmax, mmax = np.max(n), np.max(m)

theta = theta.flatten()[:, np.newaxis]
theta_rad = np.radians(theta)

P = {}
dP = {}
sinth = np.sin(d2r*theta)
costh = np.cos(d2r*theta)
sinth = np.sin(theta_rad)
costh = np.cos(theta_rad)

# Initialize Schmidt normalization
S = {}
Expand Down Expand Up @@ -325,22 +325,26 @@ def geod2geoc(gdlat, height, Bn, Bu):
a = WGS84_a
b = a*np.sqrt(1 - WGS84_e2)

sin_alpha_2 = np.sin(gdlat*d2r)**2
cos_alpha_2 = np.cos(gdlat*d2r)**2
# Convert geodetic latitude angles to radians
gdlat_rad = np.radians(gdlat)

sin_alpha_2 = np.sin(gdlat_rad)**2
cos_alpha_2 = np.cos(gdlat_rad)**2

# calculate geocentric latitude and radius
tmp = height * np.sqrt(a**2 * cos_alpha_2 + b**2 * sin_alpha_2)
beta = np.arctan((tmp + b**2)/(tmp + a**2) * np.tan(gdlat * d2r))
beta = np.arctan((tmp + b**2)/(tmp + a**2) * np.tan(gdlat_rad))
theta = np.pi/2 - beta
r = np.sqrt(height**2 + 2 * tmp + a**2 * (1 - (1 - (b/a)**4) * sin_alpha_2) / (1 - (1 - (b/a)**2) * sin_alpha_2))

# calculate geocentric components
psi = np.sin(gdlat*d2r) * np.sin(theta) - np.cos(gdlat*d2r) * np.cos(theta)
psi = np.sin(gdlat_rad) * np.sin(theta) - np.cos(gdlat_rad) * np.cos(theta)

B_r = -np.sin(psi) * Bn + np.cos(psi) * Bu
B_th = -np.cos(psi) * Bn - np.sin(psi) * Bu

theta = theta/d2r
# Convert theta to degrees
theta = np.degrees(theta)

return theta, r, B_th, B_r

Expand Down Expand Up @@ -401,7 +405,7 @@ def geoc2geod(theta, r, B_th, B_r):
A84 = 320.*E8 /2048.

GCLAT = (90-theta)
SCL = np.sin(GCLAT * d2r)
SCL = np.sin(np.radians(GCLAT))

RI = a/r
A2 = RI*(A21 + RI * (A22 + RI* A23))
Expand All @@ -418,16 +422,18 @@ def geoc2geod(theta, r, B_th, B_r):
S6CL = S2CL * C4CL + C2CL * S4CL

DLTCL = S2CL * A2 + S4CL * A4 + S6CL * A6 + S8CL * A8
gdlat = DLTCL + GCLAT * d2r
gdlat = DLTCL + np.radians(GCLAT)
height = r * np.cos(DLTCL)- a * np.sqrt(1 - E2 * np.sin(gdlat) ** 2)


# magnetic components
psi = np.sin(gdlat) * np.sin(theta*d2r) - np.cos(gdlat) * np.cos(theta*d2r)
theta_rad = np.radians(theta)
psi = np.sin(gdlat) * np.sin(theta_rad) - np.cos(gdlat) * np.cos(theta_rad)
Bn = -np.cos(psi) * B_th - np.sin(psi) * B_r
Bu = -np.sin(psi) * B_th + np.cos(psi) * B_r

gdlat = gdlat / d2r
# Convert gdlat to degrees
gdlat = np.degrees(gdlat)

return gdlat, height, Bn, Bu

Expand Down Expand Up @@ -511,8 +517,9 @@ def igrf_gc(r, theta, phi, date, coeff_fn = shc_fn):
h = h.interpolate(method = 'time').loc[date, :]

# compute cosmlon and sinmlon:
cosmphi = np.cos(phi * d2r * m) # shape (n_coords x n_model_params/2)
sinmphi = np.sin(phi * d2r * m)
phi_rad = np.radians(phi)
cosmphi = np.cos(phi_rad * m) # shape (n_coords x n_model_params/2)
sinmphi = np.sin(phi_rad * m)

# make versions of n and m that are repeated twice
nn, mm = np.tile(n, 2), np.tile(m, 2)
Expand All @@ -528,7 +535,7 @@ def igrf_gc(r, theta, phi, date, coeff_fn = shc_fn):

# calculate Bphi:
G = -(RE / r) ** (nn + 1) * mm * np.hstack((-P * sinmphi, P * cosmphi)) \
* RE / r / np.sin(theta * d2r)
* RE / r / np.sin(np.radians(theta))
Bphi = G.dot(np.hstack((g.values, h.values)).T).T # shape (n_times, n_coords)

# reshape and return
Expand Down