“The challenge with rivers is that much of the beauty and interest is hidden from view beneath the surface,” said Jack Spees, CEO of the Ribble Rivers Trust. “To reveal this beauty, we undertook a bathymetric survey of a section with particularly interesting features that is adjacent to a heavily used public footpath.”
The trust is using survey results to reveal these hidden depths on interpretation boards, including digitally augmented reality and video media enabling visitors to explore the underwater world.
For the survey, a robotically controlled 1.2-meter twin-hull shallow draft vessel powered by a twin-jet system surveyed a hectare of the riverbed. It carried depth-recording sonar and a tracking prism that enabled a Spectra Precision Focus 35 total station to lock onto and robotically follow and record the vesssel’s location.
Echo soundings were transmitted to a tablet PC ashore via long-range Bluetooth and time stamped, while the boat’s position was continuously recorded by the total station and sent back to a tablet PC, also using long-range Bluetooth and time stamped.
The tablet PC ran 4Site, a program that formatted and processed the data from the sonar and the total station into a DWG drawing. Each point was positioned in real time, so the vessel operator could ensure complete coverage. A mesh of a 200-meter section of the river with depths to 3.5 meters was combined with aerial lidar data to produce the survey.