Welcome to the Hermes GNSS Streaming Server
General RTCM info
RTCM Version 2.x
The RTCM Version 2.x standard is used to format GNSS code and phase observables. It defines a number of messages. Message types that may be of interest in the Real-time IGS context are the following:
Type 1 message is the range correction message and is the primary message in code-phase differential positioning (DGPS). It is computed in the reverence station receiver by computing the error in the range measurement for each
Type 2 message is automatically generated when a new set of satellite ephemeris is downloaded to the base receiver. It is the computed difference between the old ephemeris and the new ephemeris.
Note, Type 2 messages are used when the reference station is transmitting Type 1 messages.
Type 3 and 22 messages are the reference station position and the antenna offset.
They are used in RTK processing to perform antenna reduction.
Type 18 and 20 messages are uncorrected carrier phase data and carrier phase
Type 19 and 21 messages are the uncorrected pseudo-range measurements and
Type 23 message provides the information on the antenna type used on the
Type 24 message carries the coordinates of the installed antenna's ARP in the GNSS
coordinate system coordinates.
Note that only RTCM Version 2.2 and 2.3 streams can include GLONASS data.
The range resolution for RTCM Version 2.x is 2 cm and the phase resolution is 0.5 mm.
RTCM Version 3.x
RTCM Version 3 is a GNSS streaming format that has been developed as an alternative to RTCM 2. Service providers and vendors have asked for an improved standard that would be more efficient, easy to use, and more easily adaptable to new situations.
RTCM Version 3 defines a number of message. Message types that may be of interest in the Real-time IGS context are:
Type 1001, GPS L1 code and phase.
Type 1002, GPS L1 code and phase and ambiguities and carrier to noise ratio.
Type 1003, GPS L1 and L2 code and phase.
Type 1004, GPS L1 and L2 code and phase and ambiguities and carrier to noise ratio.
Type 1005, Station coordinates XZY for antenna reference point.
Type 1006, Station coordinates XYZ for antenna reference point and antenna height.
Type 1007, Antenna descriptor and ID.
Type 1008, Antenna serial number.
Type 1009, GLONASS L1 code and phase.
Type 1010, GLONASS L1 code and phase and ambiguities and carrier to noise ratio.
Type 1011, GLONASS L1 and L2 code and phase.
Type 1012, GLONASS L1 and L2 code and phase and ambiguities and carrier tonoise ratio.
Type 1019, GPS Ephemeris (under development).
Type 1020, GLONASS Ephemeris (under development).
Note that RTCM Version 3 today only allows to transport one code observation per frequency (i.e. CA or P1, L2C or P2). The range resolution is 2 cm and the phase resolution is 0.5 mm.
More info on RTCM messages can be found at http://www.rtcm.org. Various documentation, software and useful infromation on NTRIP Protocol is also available at (Bundesamt fur Kartographie und Geodasie - BKG), http://igs.bkg.bund.de/. Relevant information is also referred in the book "GPS and Geodetic Applications" 2nd Version. (Authors: A.Fotiou & C.Pikridas) Editions Ziti, ISBN:978-960-456-346-3 (in Greek).