Method of Using a TV Sound Multiplexed Sub-Carrier Data Link for a DGPS/RTK Service

K. Sasano, I. Petrovski, M. Ishii, H. Torimoto and B. Townsend

Abstract:	The paper presents new method of DGPS and RTK correction transmission through TV Sound Multiplexed Sub-Carrier. The presented system had been officially adopted by the Ministry of Post and telecommunications for broadcasting DGPS and RTK corrections in Japan. The results of system test and analysis are presented. Initial tests for Asahi TV system for distribution of DGPS and RTK corrections through TV audio sub channel was conducted in 1997. Since then the method had been further developed. Due to the interference issue method had been drastically modified including the implementation of other sub-carrier. The wide availability of DGPS and RTK corrections is very important to support the activity in different areas including geodetic, construction, land movement monitoring, etc. There are a number of different methods for DGPS and RTK correction transmission. The public demands include both GPS and GLONASS corrections DGPS and RTK, availability, reliability and strength of signal. The paper investigates different approaches to supply DGPS and RTK corrections. We present a short review and discussion of the requirements for DGPS and RTK. There are a number of DGPS and RTK services currently available in Japan. Comparison with other methods, that use FM radio, beacons and the Internet as a media, along with their advantages and disadvantages is presented. Paper considers technical problems of implementation, describes options for frequency band choosing, and compares different methods of available correction transmitting, underlying advantages of proposed method. Discussion of the TV sub carrier as a media for DGPS/RTK corrections is presented. The issues of frequency, coverage, encoding and decoding, error rates and latency are covered. User equipment was developed and is described in the paper. An overview of requirements for the system is presented. Specification of used TV Audio channel is presented. Operational characteristics for the channel based on the laboratory and field tests are derived. Interference issue is considered. The description of available in the world TV system is given. The system design for NTSC system that is adopted for America, Japan etc. is presented. Approach for development the similar system for PAL is given. The system now operates in a test mode in Tokyo area. DGPS and RTK corrections are available. The system will supply user with differential and RTK corrections in area approximately 100- diameter km. The system has been successfully tested and should be implemented as soon as this year. The test results on the error rates, signal latency, coverage (outages), available accuracy, interference are presented. The proposed method could be bases for worldwide approach to the RTK correction broadcast. After the first step implementation in the Tokyo area system is going to be implemented into the other areas.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	2418 - 2423
Cite this article:	Sasano, K., Petrovski, I., Ishii, M., Torimoto, H., Townsend, B., "Method of Using a TV Sound Multiplexed Sub-Carrier Data Link for a DGPS/RTK Service," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 2418-2423.
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