segyfileread.c

地震数据segy格式数据文件读取

#include "stdio.h"
#include "stdlib.h"
#include "math.h"
union Data{float a; char dat[4];};
union SI{unsigned short a; char s[2];};
union SP{unsigned short i; char s[2];};
main()
{
   short Tn;
   int i,j;
   int k;
   char ch;
   float dat;
   union SI si;//采样点数
   union SP sp;//定义采样率
   union Data data;//定义数据
   FILE *fp, *fp1;
   fp = fopen("E:\\3tk.sgy","rb");//打开SEGY数据文件
   if(!fp)
   {
	   printf("can't open fileseg!");
       exit(1);
   }
   fseek(fp,3220L,0);
   fread(si.s,2,1,fp);//读取采样点
   ch=si.s[0];
   si.s[0]=si.s[1];
   si.s[1]=ch;
   fseek(fp,3216L,0);//读取采样率
   fread(sp.s,2,1,fp);
   ch=sp.s[0];
   sp.s[0]=sp.s[1];
   sp.s[1]=ch;
   j=0;
   rewind(fp); 
   while(!feof(fp))
   {
      fread(&k,1,1,fp);
	  j+=1;
   }
   Tn = (short)((j-1-3600)/(float)(si.a*4+240));   //计算道数 
   if(!(fp1=fopen("data.dat","w+")))   //新建文本文件存储数据
   {
	   printf("can't open text file!");
       exit(1);  
   }
    fprintf(fp1,"si = %u, sp =%u, Tn =%d, j=%d\n",si.a, sp.i, Tn, j);
   for(j=0;j<2;j++)
   {
 	fprintf(fp1,"÷÷÷÷÷÷÷÷÷÷÷÷÷÷The %d trace:－－－－－－－－－－－－－－\n ", j+1);
	for(i=0;i<si.a;i++)
    {
      fseek(fp,3600L+j*240L+j*si.a*4L+240L+i*4L,0);
	  fseek(fp,3600L+240L+i*4L,0);
	  fread(data.dat,4,1,fp);
	  ch=data.dat[0];
	  data.dat[0]=data.dat[3];
	  data.dat[3]=ch;
	  ch=data.dat[1];
	  data.dat[2]=data.dat[1];
	  data.dat[1]=ch;  
	  fprintf(fp1,"%f ", data.a);
	  if((i+1)%10==0)
       fprintf(fp1,"\n");   
	  if(fabs(data.a)>1e6)
		  printf("error");
    }
	fprintf(fp1,"\n");
   }
   fclose(fp1);
   fclose(fp);
}