Real-Time Kinematic (RTK) is a method to solve navigation position by determining ambiguity included in Carrier-Phase Measurement. RTK would be very useful for Intelligent Transportation System (ITS) such as "lane control" and "autonomous vehicle control" in the vehicle, but in an urban cannon environment the RTK-based ITS navigation often loses its own position by very ordinary causes such as multipath or cycle-slip. Besides them, the time delay in correction also affects the RTK performance of moving rover. Message Type (MT) 1004 of RTCM v3.1, used as RTK correction messages, contains pseudo-range, carrier phase measurement, which include the distance from a reference station to the satellite. This message should be transmitted to the user as often as possible, because the distance in the message varies rapidly. On the other hands, Compact RTK, whose message is assigned by RTCM SC-104 as a proprietary message, MT 4081 can provide high quality GPS-RTK with a small communication bandwidth. Pseudo Range Correction (PRC) and Carrier Phase Correction (CPC) in MT 4081 change very slowly, therefore it can reduce current MT 1004 message correction data size, and more over it can compensate the time latency without a severe degradation in a low-rate datalink such as 500bps. In this paper, we construct a user receiver as a Virtual User Station (VUS) at known positions and a Correction Repeater that transmit correction messages from a reference station to the VUS. Through this testbed, we can compute current latency by comparing the GPSTime of user and that of RTCM message. Also, we can compare the position from RTK whose correction message are coming from vehicles with the true position. Finally, we implement a zero and non-zero baseline test with 30s time latency to correction repeater in static situation for comparison of time delay complementation performances between current MT 1004 message of RTK and MT 4081 message of Compact RTK. As this result, we confirmed 3.8cm horizontal RMS error, 6.5 cm vertical RMS error and that MT 1004 didn????t maintain fixed positioning while MT 4081 maintained.

Keywords: network RTK, compact RTK, ITS (intelligent transport system), RTCM (the radio technical commission for maritime services), time delay