RTCM 10403.3, Differential GNSS (Global Navigation Satellite Systems)
Services - Version 3, October 7, 2016
This standard (referred to as Version 3) has been developed by RTCM Special Committee 104 as a more
efficient alternative to the standards entitled "RTCM Recommended Standards for Differential
Recommended Standards for Differential GNSS (Global Navigation Satellite Systems) Service, Version 2.x".
(Current version is 2.3, now designated as RTCM 10402.3.) Service providers and vendors represented on
the SC104 Committee wanted a new standard that would be more efficient, easy to use, and more easily
adaptable to new situations. The main complaint was that the Version 2.x parity scheme, which uses
words with 24 bits of data followed by 6 bits of parity, was wasteful of bandwidth. Another complaint was
that the parity was not independent from word to word. Still another was that even with so many bits
devoted to parity, the actual integrity of the message was not as high as it should be. Plus, 30-bit words
are awkward to handle. The new standard, Version 3, is intended to correct these weaknesses.
Unlike Version 2.x, this standard does not include tentative messages. The messages in Version 3 have
undergone testing for validity and interoperability, and are considered to be permanent. Amendments to
the standard may change the meaning of reserved bits or provide additional clarifying text, but no changes
will be made in the data fields. Changes will require new messages to be developed. In addition to the
messages described in the current standard, the Committee continues to develop new messages, which
are described in separately published amendments, and periodically gathered into a new edition of the
standard. RTCM 10403.x for DGNSS services is proving useful in supporting highly accurate differential
and kinematic positioning as well as a wide range of navigation applications worldwide.
Note that Version 3 messages are not compatible with Version 2.x. Since many receivers have been
designed and programmed for use with Version 2.x messages, RTCM is maintaining both standards
10402.3 and 10403.3 as "current" standards.
Version 3.0:
The initial edition consisted primarily of messages designed to support real-time kinematic (RTK)
operations. The reason for this emphasis is that RTK operation involves broadcasting a lot of information,
and thus benefits the most from an efficient data format. Version 3.0 provided messages that support
GPS and GLONASS RTK operations, including code and carrier phase observables, antenna parameters,
and ancillary system parameters.
Version 3.1 (RTCM Standard 10403.1):
The next edition, Version 3.1 (RTCM Standard 10403.1), incorporated GPS Network Corrections, which
enable a mobile receiver to obtain accurate RTK information valid over a large area. In addition, new GPS
and GLONASS messages provide orbital parameters to assist in rapid acquisition. A Unicode text message
is also provided for the transmission of textual data. Finally, a set of messages are reserved for vendors
who want to encapsulate proprietary data in their broadcasts. The GPS Network Corrections enable a
mobile receiver to obtain accurate RTK information valid over a large area. The Network RTK correction
information provided to a rover can be considered as interpolated corrections between the reference
stations in the RTK network. This interpolation is not perfect and varies with the actual conditions of the
atmosphere. A residual interpolation error has to be expected. With sufficient redundancy in the RTK
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