该程序代码实现的功能是找出$GPRMC语句，计算校验和，找出其中校验正确，并且字段2表示已定位的语句，从中计算出时间，换算成北京时间。一次数据中会包含多条$GPRMC语句，以最后一条语句得到的北京时间作为结果输出。-The function of the program code to achieve is to find $GPRMC statement, calculate the checksum, find out the check is correct, and field said it had 2 positioning statement, to calculate the time, converted to Beijing time.A data will contain more than $GPRMC statement, with the last statement of Beijing time as a result the output.