以下为我的gps实际输出，checksum是星号后的数字码？
我认为这种文本输出似乎没有使用checksum的必要，丢码的话，文本肯定会解析出错，
比简单的checksum算法更容易发现错误。
$gpgsv,3,1,09,05,18,043,43,11,04,290,44,14,59,034,43,15,01,184,*70
$gpgsv,3,2,09,16,13,200,,18,22,153,,23,44,160,,25,54,288,51*7e
$gpgsv,3,3,09,30,46,061,30,,,,,,,,,,,,*45
$pgrme,45.3,m,,m,45.3,m*00
$gprmc,131558,a,2818.7145,n,10944.4235,e,000.0,000.0,1n0503,002.0,w*61
$gpgga,131558,2818.7145,n,10944.4235,e,1,04,4.6,238.2,m,-25.4,m,,*66
$gpgsa,a,2,05,11,14,,,,,25,,,,,4.6,4.6,*1a
