Product specifications

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B INARY I NTERFACE
Binary messages may be output from the Crescent Vector simultaneously as
NMEA 0183 data. Binary messages have a proprietary definition and would
likely require custom software support if you wish to use them. Binary
messages are inherently more efficient than NMEA 0183 and would be used
when you require maximum communication efficiency. Use of binary
messages for most users is not recommended - the NMEA interface allows
you to control the operation of the Crescent Vector and also receive most
types of information regarding status and positioning information.
Note: If you wish to log binary data, please ensure that your logging software
has opened the file as a binary file, otherwise you may lose data.
RTCM SC-104 P ROTOCOL
RTCM SC-104 is a standard that defines the data structure for differential
correction information for a variety of differential correction applications. It
has been developed by the Radio Technical Commission for Maritime services
(RTCM) and has become an industry standard for communication of correction
information. RTCM is a binary data protocol and is not readable via a
terminal program. It appears as ‘garbage’ data on-screen since it is a binary
format and not ASCII text. The following is an example of how the RTCM
data appears on-screen:
mRMP@PJfeUtNsmMFM{nVtIOTDbA^xGh~kDH`_FdW_yqLRryrDuhcB\@}N`ozbSD
@O^}nrGqkeTlpLLrYpDqAsrLRrQN{zW|uW@H`z]~aGxWYt@I`_FxW_qqLRryrDC
ikA\@Cj]DE]|E@w_mlroMNjkKOsmMFM{PWDwW@HVEbA^xGhLJQH`_F`W_aNsmMF
M[WVLA\@S}amz@ilIuPqx~_IZhTCpLLrYpdP@kOsmMFM[kVDHwVGbA^P{WWuNt_
SW_yMsmMnqdrhcC\@sE^ZfC@}vJmNGAHJVhTCqLRryrdviStW@H_GbA^P{wxu[K
RTCM has various levels of detail, however the highest level is the message.
RTCM defines numerous messages that contain specific information. The
Crescent Vector module processes the C/A code and does not support more
advanced methods of differential positioning, such as real-time kinematic
(RTK) that uses different RTCM message types. Considering this fact, only
certain RTCM messages are important for use with the Crescent Vector:
• Type 1 and Type 9 messages, both of which contain similar information. These two
messages contain pseudorange corrections and range rate corrections to each GPS
satellite.
• The Type 2 message contains delta differential corrections that are used when the
remote receiver is using a different satellite navigation message than used by the base
station.
• The Type 5 message contains GPS constellation health information used for improving
tracking performance of a GPS receiver
• The Type 6 message contains null information, and is broadcast so that a beacon
receiver demodulating the data from the broadcast does not lose lock when the beacon
station has no new data to transmit.
Note: RTCM is a local area data standard. This means that when positioning
with an external source of corrections or outputting corrections from the
Crescent Vector to another GPS receiver, performance will degrade as a
function of distance from the base station. The additional degradation will
depend on the difference in observed orbit and ionospheric errors between the