    typedef struct {
      int sweep_num;      /* Integer sweep number. */
      float elev;         /* Elevation angle (mean) for the sweep. */
      float beam_width;   /* This is in the ray header too. */
      float vert_half_bw; /* Vertical beam width divided by 2 */
      float horz_half_bw; /* Horizontal beam width divided by 2 */
      int nrays;
      float (*f)(Range x); /* Data conversion function. f(x). */
      Range (*invf)(float x); /* Data conversion function. invf(x). */
    } Sweep_header;