GEO_poly_fit.c

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/* file: poly_fit.c */ 
 
#include "PGS_MODIS_35251.h"
#include "smfio.h"
#include "GEO_geo.h"
#include "GEO_util.h"
 
int GEO_poly_fit(
    double const    *coef,  
    double      const in_x, 
    int     const degree,
    double      * const out_fit
)
/*
!C*****************************************************************************
!Description:   subroutine in the utility functions of the Level-1A geolocation
                software to evaluate a polynomial.
 
!Input Parameters:
        double *coef - the array of coefficients for the polynomial
        double in_x - the input independent variable x
        int degree - the degree of the polynomial
 
!Output Parameters:
        double *out_fit - the output value
 
Call functions: modsmf(MODIS_X_MNEMONIC_STRING, "user message string", "function,
                GEO_poly_fit.c") - writes error status messages to log
 
!Revision History:
        $Log: GEO_poly_fit.c,v $
        Revision 6.1  2011/02/14 21:34:00  kuyper
        Corrected const qualification of parameter which points at input data.
 
        Revision 1.6  1997/07/21 16:24:34  kuyper
        Baselined Version 1
 
 * Revision 1.6  1997/03/26  18:10:52  fhliang
 * Initial revision of SDST delivery of GEO_poly_fit.c.
 *
        Revision 1.5  1997/02/13 19:52:19  kuyper
        Merged seed files.
 
        Revision 1.4  1996/07/24 21:09:07  kuyper
        Standardized order of #include files.
        Declared arguments const.
 
        Revision 1.3  1996/07/23 23:30:28  kuyper
        Inserted required '!'s in comments.
        Changed constants to double, to avoid conversions.
 
        Revision 1.2  1996/07/18 19:54:18  kuyper
        Included self-checking header file.
        Added other required header file.
        James Kuyper Jr (kuyper@ltpmail.gsfc.nasa.gov)
 
        10/10/95
        Tracey W. Holmes
        Added debug option. 
 
        6/30/95
        Tracey W. Holmes (holmes@modis-xl.gsfc.nasa.gov)
        Added SDP error messages.
 
        6/12/95
        Frederick S. Patt (patt@modis-xl.gsfc.nasa.gov)
        Revised prolog and initialized internal variables
                
        4/5/95
        Ruiming Chen
        Finished coding
 
!Team-unique Header:
                This software is developed by the MODIS Science Data Support
                Team for the National Aeronautics and Space Administration,
                Goddard Space Flight Center, under contract NAS5-32373.
 
!END*************************************************************************
*/
{
 
  double x_power_degree = 1.0;  /* degree power of x */
  int i = 0;  /* iteration parameter */
 
  if (degree <= 0)  {
    /* write to SDP event message */
    modsmf(MODIS_E_UTIL_POLY, "", "GEO_poly_fit, GEO_poly_fit.c");
 
    return FAIL;
  }
 
  if (degree > MAX_POLY_DEGREE)  {
    /* write to SDP event message */
    modsmf(MODIS_E_UTIL_MAX_POLY, "", "GEO_poly_fit, GEO_poly_fit.c");
 
    return FAIL;
  }
 
  /* initialize out_fit */
  *out_fit = 0.0;
 
  /* calculate the fit number */    
  for (i = 0; i <= degree; i++)  {
    *out_fit += coef[i]*x_power_degree; 
    x_power_degree = x_power_degree * in_x;
  }
 
  return SUCCESS;
}