/* 
Transform Station Data for GrADS Station Model Plot Into Binary
Initial C program provided by the Center for Ocean-Land-Atmosphere Studies at George Mason University
Code expanded and modified by Dorian J. Burnette

Name of Input File = stationdata.txt
Name of Output File = stationdata.dat

Structure of Input File:
Space-delimited with No Header
Variables In Following Order by Columns: 
-Year Month Day Hour StationID Lat Lon Temperature Dewpoint Pressure WindDirection WindSpeed CloudCover Visibility WeatherSymbol PressureChange
StationID Character Limit = 6
Units: Time (UTC), Temperature (degrees F), Dewpoint (degrees F), Pressure (mb), Wind Direction (degrees), Wind Speed (knots), Visibility (SM)
Cloud Cover (enter GrADS values): 20=clear, 21=scattered, 22=broken, 23=overcast, 24=obscured, 25=missing (M plotted)
Weather Symbols (enter GrADS values, see chart):
-thunder/sleet/freezing/hurricane [used in symbols 1-13,24-27,31-32,38,40,41]
-rain/drizzle [used in symbols 3,8,12-18,24,26-30,37]
-snow [used in symbols 4,9,19-23,37]
-fog [used in symbol 34]
-blowing snow/sand/smoke [used in symbols 33,35,36,39]
If weather variables (temperature, dewpoint, etc.) are missing, enter -999 in the respective columns
*/

#include <stdio.h>
#include <math.h>
#define PI 3.141592654
 
/* Station Data Report Header Structure */
struct rpthdr {
  char  id[6];    /* Station ID */
  float lat;      /* Latitude of Station */
  float lon;      /* Longitude of Station */
  float t;        /* Time in grid-relative units */
  int   nlev;	  /* Number of levels following */
  int   flag;     /* Level independent var set flag */
} hdr;
 
main ()
{
  FILE  *ifile, *ofile;
  char  rec[150];
  int   flag,year,month,day,hour,yrsav,mnsav,ddsav,hhsav,i;
  float temp,dp,press,winddir,windsp,cld,vis,wx,pressdelta,windu,windv;
 
/* Open Files */
  ifile = fopen ("stationdata.txt","r");
  ofile = fopen ("stationdata.dat","wb");
  if (ifile==NULL) {
    printf("\nError opening input text file.\n");
    return;
  }
  if (ofile==NULL) {
    printf("\nError opening output binary file.\n");
    return;
  }
 
/* Convert Station Data Text File Into GrADS Binary File */
  printf("\nConverting station data to binary...");
  flag = 1;
  while (fgets(rec,sizeof(rec),ifile)!=NULL) {
    /* Read Station Report */
    sscanf (rec,"%i %i %i %i %s %g %g %g %g %g %g %g %g %g %g %g",&year,&month,&day,&hour,hdr.id,&hdr.lat,&hdr.lon,&temp,&dp,&press,&winddir,&windsp,&cld,&vis,&wx,&pressdelta);
    /* Time Group Terminator...If Needed */
    if (flag) {
      yrsav = year;
      mnsav = month;
      ddsav = day;
      hhsav = hour;
      flag = 0;
    }
    if (yrsav!=year || mnsav!=month || ddsav!=day || hhsav!=hour) {
      hdr.nlev = 0;
      fwrite(&hdr,sizeof(struct rpthdr), 1, ofile);
    }
    yrsav = year;
    mnsav = month;
    ddsav = day;
    hhsav = hour;
	/* Transform Wind Direction and Wind Speed Into U and V Vectors for GrADS */
	winddir = 270-winddir;
	if (winddir<0) winddir = winddir + 360;
	winddir = (winddir * PI) / 180;
	windu = windsp * cos(winddir);
	windv = windsp * sin(winddir);
    /* Write Station Report */
    hdr.nlev = 1;
    hdr.flag = 1;
    hdr.t = 0.0;
    fwrite (&hdr,sizeof(struct rpthdr), 1, ofile);
    fwrite (&temp,sizeof(float), 1, ofile);
	fwrite (&dp,sizeof(float), 1, ofile);
	fwrite (&press,sizeof(float), 1, ofile);
	fwrite (&windu,sizeof(float), 1, ofile);
	fwrite (&windv,sizeof(float), 1, ofile);
	fwrite (&cld,sizeof(float), 1, ofile);
	fwrite (&vis,sizeof(float), 1, ofile);
	fwrite (&wx,sizeof(float), 1, ofile);
	fwrite (&pressdelta,sizeof(float), 1, ofile);
  }
  /* End of Station Data...Write Final Terminator */
  hdr.nlev = 0;
  fwrite (&hdr,sizeof(struct rpthdr), 1, ofile);
  /* Close Station Data Files */
  fclose (ifile);
  fclose (ofile);
  printf("done\n");
  printf("\nRun completed successfully.\n");
  /* Display STNMAP Utility Reminder */
  printf("Reminder: Run the STNMAP utility within the GrADS directory to create a station map file that allows GrADS to access the station data more efficiently.\n\n");
}