Real time digital data communication system for a remotely operated ADCP

An acoustic Doppler current profiler is moored adjacent to the Miami Offshore Dredged Material Disposal Site to monitor in real-time ocean currents during dredge disposal operations. By combining hardwired cable and radio transmission techniques, a remote telemetry system was designed and installed at a fixed navigational marker that provides system reliability and a stable platform to work from. Most ADCP systems that provide real-time data are cabled back to a recording site which also supplies power to the ADCP down the cable. A self powered ADCP was utilized since cabling to shore was not a viable option. This presented problems in powering the interface to the data cable and had to be overcome. Powering down the cable was limited since the telemetry unit at the other end of the cable also had to be battery powered. From the ADCP a cable was laid to the closest fixed workable point, which happened to be a navigation marker at the entrance to the Port of Miami. This cable extends approximately three miles, and proper cable drivers had to be located that would deal with this distance. At the navigation marker, a telemetry unit was designed that buffers the received data from the ADCP cable by using a micro controller, and then transmits this data by a UHF radio modem. The data is received and stored by computer at our laboratory approximately five miles away. Power consumption proved to be a major concern, since there are no available power sources at the navigation marker. The ADCP operates from its own internal battery pack, and the telemetry unit was designed to operate from batteries with solar panels to supplement the power. It is able to operate for months unattended. The system was installed in June of 1995, and has since proved to be an extremely reliable system