EGM96 Geoid Fortran to C

f477.c

void main(){
  double AR = AE / RE,
      ARN = AR,
      AC = 0.0,
      A = 0.0,
      B = 0.0;
  int K = 3;
  for(int N = 2; N <= NMAX; N++){ // DO 030 N=2,NMAX
    ARN *= AR;
    K++;
    double SUM  = P[K] * HC[K]; // HC from EGM96, M = 0
    double SUMC = P[K] * CC[K]; // CC from CORRCOEF, M = 0
    for(int M = 1; M <= N; M++){ // DO 020 M=1,N
      K++;
      SUM  += P[K] * (HC[K] * COSML[M] + HS[K] * SINML[M]);
      SUMC += P[K] * (CC[K] * COSML[M] + CS[K] * SINML[M]);
    } // 20
    A  += SUM * ARN;
    AC += SUMC;
  } // 30
  AC += CC[1] + (P[2] * CC[2]) + (P[3] * (CC[3] * COSML[1] + CS[3] * SINML[1])); // (n = 0, m = 0), (n = 1, m = 0/1)
  UNDU = A * GM / (GR * RE);
  // ADD HACO (=AC/100) TO CONVERT HEIGHT ANOMALY ON THE ELLIPSOID TO THE UNDULATION
  // ADD -0.53M TO MAKE UNDULATION REFER TO THE WGS84 ELLIPSOID.
  UNDU += (AC / 100.0E0) - 0.53E0;
}