Radio Technical Commission for Maritime Services
The Radio Technical Commission for Maritime Services ( RTCM ) is an American organization that was founded in 1947 with the aim of creating the basis and standardization of maritime telecommunications .
SC-104
The RTCM has become known in particular for the GPS- related standard for the transmission of corrections for GNSS applications. It contains data elements, time intervals between transmissions, data segment sizes, units and resolution of the parameters to be transmitted, the format of which is defined in various data types. It was developed by Special Committee number 104 ( SC-104 ) and first presented as a recommendation in 1985.
development
The first definition of a standard was created for so-called DGPS applications. In the original specification of GPS, only a navigation accuracy of 100 meters was provided for civil applications. For this purpose, the so-called Selective Availability (S / A) was developed in the 1990s . Essentially, this is an artificial deterioration in the achievable measurement accuracy due to cyclical satellite clock errors that were not reported by the system and could therefore not be corrected directly.
Differential measurement methods had been known from the field of geodesy since the 1980s. With the differential method using GPS, one assumes identical or similar errors at two measuring stations. Since the artificial deterioration of the satellite signal is measured as the same quantity by all stations, this error can be eliminated again by calculating the difference between observations made by two stations on the same satellites.
The SC-104 has meanwhile expanded the standard for various applications. In addition to DGPS corrections, there are also different methods for so-called real - time kinematics applications (RTK). While DGPS achieves an accuracy of approximately one meter, RTK applications deliver accuracy of up to centimeters.
Designation of the standardizations for the data protocol for the transmission of the correction data:
- RTCM SC-104 version 1.0 (1985)
- RTCM SC-104 version 2.0 (1990)
- RTCM SC-104 version 2.1 (1994)
- RTCM SC-104 version 2.2 (1998)
- RTCM SC-104 version 2.3 (2001)
- RTCM SC-104 version 3.0 (2004)
- RTCM SC-104 version 3.1 (2009)
- RTCM SC-104 version 3.2 (2013)
- RTCM SC-104 version 3.3 (2016)
literature
- Kendal Furgerson: RTCM / Special Committee 104, Current Status and Focus . Presented: International Symposium on GNSS, Space-based and Ground-based Augmentation Systems and Applications, November 29-30, 2010, Brussels, Belgium ( PDF ).
- Gerhard Wübbena, Martin Schmitz, Andreas Bagge: Real-Time GNSS Data Transmission Standard RTCM 3.0 . Presented: IGS Workshop 2006 "Perspectives and Visions for 2010 and beyond", May 8-12, 2006, ESOC, Darmstadt, Germany ( PDF ).