RTKLIB之RTCM解析

1.格式
rtcm3 message format:

*            +--------------+-----------+-------------+------------------------+-----------+

*            | preamble | 000000 |  length   |    data message    |  parity  |

*            +--------------+-----------+-------------+-------------------------+----------+

*            |<---8bit -->|<-6bit ->|<-10bit ->|<--- length x 8 ---->|<-24bit->|


例子:1005 message解析

(1)preamble: 0xD3
(2)reserve: 0x00=0000 0000
(3)len: 0x013=00 0001 0011=19 Bytes
(4) Message Number: 0x3ED=1005 (十进制)
(5) Reference Station ID: 0x7D3=2003(十进制)
(6)Reserved for ITRF Realization Year: 0x02=00000010 取0x02高6位,即0
(7)GPS Indicator: 0x02=00000010        取0x02低第2位,即为1,表示为支持GPS service
(8)GLONASS Indicator:同理取0x02=00000010, 表示不支持Gloass service
(9) Reserved for Galileo Indicator: 0x02=00000010, 保留位
(10)Reference-Station Indicator: 0x02=00000010
(11)Antenna Reference Point ECEF-X: 0x02980EDEEF=11,141,045,999*0.0001 =1114104.5999m 
(12)Single Receiver Oscillator Indicator:0x34=00110100
(13)Reserved: 0x34=00110100
(14)Antenna Reference Point ECEF-Y: 0x34B4BD62AC,由于最高位为1表示为负数,所以要取反加1得0xB4B429D=48507297108=>48507297108*0.0001=-(4850729.7108m),最终结果加负号.
(0x34B4BD62AC =11 0100 1011 0100 1011 1101 0110 0010 1010 1100=00 1011 0100 1011 0100 0010 1001 1101 0101 0011=0xB4B429D=48,507,297,107)
(15)Quarter Cycle Indicator:0x09=00001001
(16)Antenna Reference Point ECEF-Z: 0x0941986F33=39,755,214,3=>3975521.43m

总结:
(1)解析报文流程如下:
a.先解析message type字段,找到对应得message type具体是什么

c.DF(Data Filed)
找到DF得解释和单位,比如DF025