Efficient Transmission Technique of Compact RTK Correction Messages for Low-rate RTK Data-link

Current RTK-GPS protocols like RTCM SC-104 v.2.3, 3.0(Draft 15) and Trimble CMR require at least 2400bps-bandwidth of RTK-GPS data-link. Unlike the RTK-GPS correction messages of the RTCM SC-104 v.2.3, those of the RTCM SC-104 version 3.0(Draft 15) and the Trimble CMR have optimized structures. But they neither consider the effect of latency on corrections, nor make full use of the S/A(Selective Availability) termination. In this paper, we propose new RTK-GPS correction messages compatible with the RTCM SC-104 version 3.0(Draft 15) and describe the efficient transmission technique of the proposed RTK-GPS correction messages. By taking full advantage of the compactness of the RTCM SC-104 v. 3.0(Draft 15) and lowering update rate of the RTK -GPS corrections, we can lower the required baud rate of RTK-GPS data-link up to 600 bps or less. Transmission periods of corrections can be much lengthened by S/A termination. In order to verify the above strategy, we performed RTK-GPS experiments with simulated low-rate RTK data-link(less than 600bps). We used the SNUR-2000 v. 2.2 as RTK-GPS protocol. Then, we evaluated the performance of the SNUR-2000 v. 2.2 and the efficient transmission technique of the RTK-GPS corrections.