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RTCM Data Format ( R adio T echnical C ommission for M aritime Services). Overview of Common GPS Data Format. RINEX Raw GPS static data format for data processing and archive NMEA Standard related to data communication between marine electronic devices.
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RTCM Data Format (Radio Technical Commission for Maritime Services)
Overview of Common GPS Data Format • RINEX • Raw GPS static data format for data processing and archive • NMEA • Standard related to data communication between marine electronic devices. • Transmission of GPS position from GPS receiver to other devices (e.g. GPS receiver to PDA) • For real time positioning • RTCM SC-104 • Transmission of GPS correction from GPS reference station to GPS Rover • For DGPS/RTK surveys
Outline • Example of using RTCM Data Format • About RTCM • RTCM Data Structure • RTCM Message Types
RTCM using in SatRef • SatRef System • DGPS • Single-RTK • Network-RTK All GPS corrections from SatRef are in RTCM-2.1 data format.
Radio Technical Commission for Maritime Services • Various Special Committees set the standards for International maritime radionavigation and radiocommunication Examples: • GPS Applications • Electronic Charts…..
What is RTCM SC-104 ? • RTCM Special Committee (SC) 104 is the one concerned GPS correction signal. • RTCM data format related to GPS corrections is called RTCM SC-104 data format. • Compact binary data • good for real-time processing
What is RTCM SC-104 ? Different versions • RTCM-2.0 (Code correction ->DGPS) • RTCM-2.1 (Code + Phase correction -> RTK) • RTCM 2.2 ( …+ GLONASS ) • RTCM 2.3 ( ….+ GPS Antenna Definition) • RTCM 3.0 (….+ Network RTK & GNSS)
RTCM Data Structure (Versions 2.0-2.3)
RTCM Data Structure • Each data record contains several message types for various contents. • Message 1, Message2…. Message N • Each message comprises header and body • Header: message type, time, length of message, • Body: data for every data type
RTCM Message Types 18-21 messages added in RTCM2.1 23-24 messages added in RTCM2.3 31-36 messages added in RTCM2.2
RTCM Message Types 31-36 messages added in RTCM2.2
RTCM Raw Data Binary data
RTCM Message Type 1 1. Pseudorange Corr. 2. Range Rate Corr.
RTCM version 3.0 • RTCM 3.0 • New data structure developed for network RTK applications. • new signals L2C and L5 • GNSS system data • Compact Data Structure • RTCM 2.0 – 0.5 kbit / sec. (DGPS) • RTCM 2.1-2.3 requires 5 kbit / sec (DGPS+RTK) • RTCM 3.0.requires 2 kbit / sec
References • RTCM Recommended Standards for Differential NAVSTAR GPS service www.navcen.uscg.gov/pubs/dgps/rctm104/Default.htm • RTCM Official Website http://www.rtcm.org/ • DGPS Data Formats 2.0 www.geopp.de/download/DGPS-data-formats2.pdf • Reference Station Network Information Distribution http://www.network-rtk.info/euler/euler.html