NASA Ocean Color

ocssw V2022
 import numpy as np
  
 def derive_orbitparams(posr, velr):
  
     # adapted from Fred Patt's IDL routine get_ephem_from_hkt.pro
     omegae = 7.29211585494e-5
     for i in np.arange(len(posr)):
         velr[i][0] += posr[i][1]*omegae
         velr[i][1] -= posr[i][0]*omegae
  
     # adapted from Fred Patt's IDL routine orb2lla.pro
     re = 6378.137      # Earth equatorial radius (km)
     rem = 6371.0       # Earth mean radius (km)
     f = 1./298.257     # Earth flattening factor
     omf2 = (1.0-f) * (1.0-f)
  
     xyz = np.array([p/1000.0 for p in posr], dtype=np.float64)  # convert meters to km
     x, y, z = [xyz[:,i] for i in np.arange(3)]  # separate coords
  
     # Compute longitude
     lon = np.arctan2(y, x)
  
     # Compute geodetic latitude
     rad = np.linalg.norm(xyz,axis=1)  # Euclidean distance
     omf2p = (omf2*rem + rad - rem)/rad
     pxy = x*x + y*y
     temp = np.sqrt(z*z + omf2p*omf2p*pxy)
     lat = np.arcsin(z/temp)
  
     # Compute altitude
     clatg = np.cos(np.arctan(omf2*np.tan(lat)))
     rl = re*(1.0-f)/np.sqrt(1.0-(2.0-f)*f*clatg*clatg)
     alt = rad - rl
  
     # return as dictionary
     orbitparams = {}
     orbitparams['posr'] = posr
     orbitparams['velr'] = velr
     orbitparams['lon']  = np.rad2deg(lon)
     orbitparams['lat']  = np.rad2deg(lat)
     orbitparams['alt']  = alt * 1000.0  # convert from km to meters
  
     return orbitparams
derive_orbitparams.derive_orbitparams
def derive_orbitparams(posr, velr)
Definition: derive_orbitparams.py:3