Applications and Impact of RTCM SC-104 Type 9 Messages

David R. Cragg, Joseph W. Spalding, James E. Robbins and Greg T. Kremer

Abstract:	The RTCM SC-104 DGPS Standard includes a number of messages necessary for a differential GPS service. The type 9 message is intended to provide more frequent corrections for satellites with rapidly changing pseudorange correction rates. Selective Availability is the most frequent cause of rapid changes in pseudorange corrections. We also see an application for the use of type 9 messages when using medium frequency radiobeacon broadcasts during periods of high atmospheric noise. We have tested the performance of type 9 messages, making use of actual satellite pseudoranges during periods of operational SA. The USCG Research Reference Station was run with and without type 9 messages using the same pseudorange measurements. The resulting differential position solutions were analyzed for a number of cases and performance was compared. The loss rate for type 9 messages during high noise periods was tested and compared against loss rates for other message types. The algorithm for RTCM type 9 differential message generation is described in detail. The effectiveness of type 9 messages is evaluated as a function of broadcast data rate, signal strength, and atmospheric noise. The impact of type 9 message generation on reference station design is discussed. In particular, the importance of an atomic frequency standard is detailed.
Published in:	Proceedings of the 4th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1991) September 11 - 13, 1991 Albuquerque, NM
Pages:	537 - 546
Cite this article:	Cragg, David R., Spalding, Joseph W., Robbins, James E., Kremer, Greg T., "Applications and Impact of RTCM SC-104 Type 9 Messages," Proceedings of the 4th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1991), Albuquerque, NM, September 1991, pp. 537-546.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In