RTKLIB中readobsnav()函数之——sortobs()

sortobs()函数：

       note：是对读取出来的GNSS观测数据进行排序，并删除重复数据

       argv：obs_t *obs

       return：历元数

qsort()函数的排序后效果：

/* sort and unique observation data --------------------------------------------
* sort and unique observation data by time, rcv, sat
* args   : obs_t *obs    IO     observation data
* return : number of epochs
*-----------------------------------------------------------------------------*/
extern int sortobs(obs_t *obs)
{
    int i,j,n;
    
    trace(3,"sortobs: nobs=%d
",obs->n);
    
    if (obs->n<=0) return 0;
    
    qsort(obs->data,obs->n,sizeof(obsd_t),cmpobs);    /* 先用qsort()函数进行排序  */
    
    /* delete duplicated data */                      /*  删除重复的观测数据   */
    for (i=j=0;i<obs->n;i++) {
        if (obs->data[i].sat!=obs->data[j].sat||
            obs->data[i].rcv!=obs->data[j].rcv||
            timediff(obs->data[i].time,obs->data[j].time)!=0.0) {
            obs->data[++j]=obs->data[i];
        }
    }
    obs->n=j+1;
    
    for (i=n=0;i<obs->n;i=j,n++) {                     /*  通过时间对历元进行计数   */
        for (j=i+1;j<obs->n;j++) {
            if (timediff(obs->data[j].time,obs->data[i].time)>DTTOL) break;
        }
    }
    return n;
}