Research And Implementation Of DGNSS Correction Message Broadcasting System Based On AIS Base Station

AIS is Automatic Identification System, it is composed of shore (station) facilities and shipborne equipment, which is a new type of digital aids to navigation systems. AIS work in VHF band, using SOTDMA, broadcast static information and dynamic information of the ship to the nearby ship and shore station. AIS is almost free from outside influence, which can effectively improve the safety of the ship, plays a very important role in ship navigation, communications, collision avoidance, sea rescue, maritime and other aspects of the investigation.GNSS module provides location information to the AIS system, in order to transmit position reports. In offshore and narrow fairways, high positioning accuracy can make to improve the reliability and dependability of AIS. GNSS positioning technology is affected by many factors, there will be some errors, while errors can be reduced by DGNSS. At present, because of existing coastal DGNSS system differential signal broadcast on IF channel, IF receiver is not force to install on ship, therefore, the scope of its application is limited,but AIS boat station is forced to install, research on the use of AIS base stations to expand the scope of DGNSS is necessary and feasible. This paper studies DGNSS system based AIS base stations, mainly includes three aspects, one is designe the location of the base station calculate software, to determine the corresponding base station FATDMA slot schedule based on IALA A-124Recommendation; The second is designe FATDMA slot occupancy rules that DGNSS used to send information, and ensure that the time and frequency to meet the requirements of DGNSS; The third is to restore the AIS mobile station via AIS channel the received signal into a binary DGNSS RTCM data format, directly to DGNSS shipboard equipment, improve ship positioning accuracy.In this papper, the application software consists of two parts, one in the windows environment, use QT to development cell number calculation software; The second is use Keil to development DGNSS message reception and processing software. In AIS base stations, The RTCM SC-104format signal differential reference desk, in accordance with ITU-RM.1371AIS messages encoded using the slot occupied FATDMA, broadcast binary message. In AIS mobile station, The AIS binary message has been decoded, according to RTCM SC-104format restored to DGNSS information provided directly to DGNSS shipborne equipment, improve positioning accuracy GNSS receiver.The contents of this thesis are a part of research of National Support Program "key technology and system development of AIS/GNSS ship borne navigational equipment (2012BAH36B02) undertaken by the Institute of Navigation".