NASA Ocean Color

ocssw V2022
 #include <math.h>
 #include "l1.h"
  
 static float raddeg = 180. / PI;
  
 int ll2vec(float *ll, float *vec)
 /*******************************************************************
  
    ll2vec
  
    purpose: convert lat, lon (or az, ele) into vectors in x, y, z
  
    Returns type: int - 0 if all is OK
  
    Parameters: (in calling order)
       Type              Name            I/O     Description
       ----              ----            ---     -----------
       float *           ll               I      latitude longitude pair
       float *           vec              O      x, y, z vector with x
                                                 along the 0 lat, lon,
                                                 y at 0 lat, 90 lon and z
                                                 at 90 lat
                   (assumed to exist - array passed in)
  
    Modification history:
       Programmer        Date            Description of change
       ----------        ----            ---------------------
       W. Robinson       10 Sep 2010     Original development
  
  *******************************************************************/ {
     int32_t err;
     float latr, lonr;
  
     if ((*ll > 90.) || (*ll < -90.)) {
         *vec = -999.;
         *(vec + 1) = -999.;
         *(vec + 2) = -999.;
         err = -1;
     } else {
         latr = *ll / raddeg;
         lonr = *(ll + 1) / raddeg;
         /*
          *  get the components
          */
         *vec = cos(lonr) * cos(latr);
         *(vec + 1) = sin(lonr) * cos(latr);
         *(vec + 2) = sin(latr);
         err = 0;
     }
     return err;
 }
  
 int vec2ll(float *vec, float *ll)
 /*******************************************************************
  
    vec2ll
  
    purpose: convert a vectors in x, y, z into lat, lon (or az, ele)
  
    Returns type: int - 0 if all is OK
  
    Parameters: (in calling order)
       Type              Name            I/O     Description
       ----              ----            ---     -----------
       float *           vec              I      x, y, z vector with x
                                                 along the 0 lat, lon,
                                                 y at 0 lat, 90 lon and z
                                                 at 90 lat
       float *           ll               O      latitude longitude pair
                   (assumed to exist - array passed in)
  
    Modification history:
       Programmer        Date            Description of change
       ----------        ----            ---------------------
       W. Robinson       10 Sep 2010     Original development
  
  *******************************************************************/ {
     int32_t err;
     float lonr, latr, vls, vlen;
  
     vls = pow(*vec, 2.) + pow(*(vec + 1), 2.) + pow(*(vec + 2), 2.);
     if (vls <= 0) {
         *ll = -999.;
         *(ll + 1) = -999.;
         err = -1;
     } else {
         /*
          *  get the vector lengths for normalization and derive lat, lon
          */
         vlen = sqrt(vls);
         latr = asin(*(vec + 2) / vlen);
         lonr = atan2(*(vec + 1) / vlen, *vec / vlen);
  
         *ll = latr * raddeg;
         *(ll + 1) = lonr * raddeg;
         err = 0;
     }
     return err;
 }
ll2vec
int ll2vec(float *ll, float *vec)
Definition: ll2vec.c:6
#define PI
Definition: l3_get_org.c:6
fix_mac_rpath.err
err
Definition: fix_mac_rpath.py:21
l1.h
vec2ll
int vec2ll(float *vec, float *ll)
Definition: ll2vec.c:53