def mv2hh(mv, ks, theta, dB=True):
"""
Input:
mv: soil moisture (v/v)
ks: microwave roughness
theta: incidence angle (degree)
Output:
hh: backscatter coefficient
"""
ep = mv2ep(mv)
gamma0 = ep2gamma(ep)
g = 0.7 * (1 - np.exp(-0.65 * ks**1.8))
q, p = foreward_model(ks, gamma0, theta, dB=False)
gamma_h = horizontal_fresnel(ep, theta)
gamma_v = vertical_fresnel(ep, theta)
hh = g * np.sqrt(p) * np.cos(np.radians(theta))**3 * (gamma_v - gamma_h)
if dB:
hh = 10 * np.log10(hh)
return hh
def mv2hh(mv, ks, theta, dB=True):
"""
Input:
mv: soil moisture (v/v)
ks: microwave roughness
theta: incidence angle (degree)
Output:
hh: backscatter coefficient
"""
ep = mv2ep(mv)
gamma0 = ep2gamma(ep)
g = 0.7*(1-np.exp(-0.65*ks**1.8))
q, p = foreward_model(ks, gamma0, theta, dB=False)
gamma_h = horizontal_fresnel(ep, theta)
gamma_v = vertical_fresnel(ep, theta)
hh = g*np.sqrt(p)*np.cos(np.radians(theta))**3*(gamma_v-gamma_h)
if dB:
hh = 10*np.log10(hh)
return hh
mv = ep2mv(ep)
# estimate ks
# convert from dB to linear
q = 10**(q / 10.0)
ks = -np.log(1 - q / (0.23 * np.sqrt(gamma0)))
return mv, ks
if __name__ == "__main__":
# fig 11 and 12 of Oh(1992)
theta = 40
mv = 0.25
ep = mv2ep(mv)
gamma0 = ep2gamma(ep)
ks = np.linspace(0, 7)
q, p = foreward_model(ks, gamma0, theta)
#plt.plot(ks,q)
#plt.show()
#plt.plot(ks,p)
#plt.show()
# inverse modelling
ks = 0.1
theta = 40
mv = 0.35
ep = mv2ep(mv)
q: (dB)
theta: incidence angle (degree)
"""
guess_ks_gamma0 = [0.2, 0.4]
ks_gamma0 = fmin(res_ks_gamma0, guess_ks_gamma0, args=(p, q, theta), disp=False)
ks = ks_gamma0[0]
gamma0 = ks_gamma0[1]
return ks, gamma0
def inverse_oh1994(p, q, theta):
"""
"""
ks, gamma0 = estimate_ks_gamma0(p, q, theta)
ep = gamma2ep(gamma0)
mv = ep2mv(ep)
return mv, ks
if __name__ == "__main__":
mv = 0.15
ks = 0.3
theta = 40
ep = mv2ep(mv)
gamma0 = ep2gamma(ep)
p,q = foreward_model(ks, gamma0, theta)
print inverse_oh1994(p, q, theta)