Specifications

34 Z-Family Technical Reference Manual
Message size
Table 3.6 lists the message size for RTCM messages 18 & 19 or 20 & 21.
Table 3.7 lists the message size for Ashtech DBN messages.
ceil (3.1) = 4
Required Radio Rate
For RS232 communications, 1 start bit and 1 stop bit is required for each byte. The
required number of bits is 10/8 times the number of message bits.
For RTCM, the data is packed in 6/8 format. The required number of bits is 8/6 times
the number of bits in the message.
For RTCM data on an RS232 link, the required number of bits is 8/6*10/8 times the
number of bits in the message.
Table 3.8 lists the minimum baud rates, for a receiver sending RTCM 18 & 19 or 20
& 21 messages only.
Table 3.6: Message Size for RTCM Messages 18 & 19 or 20 & 21
Number
of
Satellites
Number of RTCM Words in
Message Type 18/20.
(30 bits/word)
Number of RTCM Words
in Message Type 19/21.
(30 bits/word)
7 (2+1+7)*2 = 20 (2+1+7)*2 = 20
9 (2+1+9)*2 = 24 (2+1+9)*2 = 24
12 (2+1+12)*2 = 30 (2+1+12)*2 = 30
Table 3.7: Message Size For Ashtech DBN Messages
Number of
Satellites
Number of Bits in DBN Message
Number of bytes in DBN
Messages
7 17*8+ceil((94+72*2*7)/16)*16 = 1240 155
9 17*8+ceil((94+72*2*9)/16)*16 = 1528 191
12 17*8+ceil((94+72*2*12)/16)*16 = 1960 245
Table 3.8: Minimum Baud Rates for RTCM Messages 18 & 19 or 20 & 21
Number of
Satellites
Minimum baud rate
(message period = T)
Minimum standard
baud rate (T = 5 sec)
Minimum standard
baud rate (T = 1 sec)
7 20*30*2*8/6*10/8*1/T 600 bps 2400 bps
9 24*30*2*8/6*10/8*1/T 600 bps 2400 bps