3D Sonar Modelling Tool for NYCDEP’s Manhattan Pumping Station
In 2010, SeaView Systems was contracted to perform work in an awkward location that required high precision. The task on this occasion was to measure the internal surfaces of a large sewage surge tower transmitting raw sewerage from lower Manhattan, NY to a processing station on Long Island, NY.
The purpose of the measurement was to specify a plug to isolate a pumping gallery from the main line. Accuracy of better than 1/2″ over an approximately 9ft diameter conduit was required.
In order to ensure proper calibration of the profiling sonar and to build confidence in the sonars ability to achieve the required accuracies, we performed extensive testing of the sonar in our test tank against targets of known distance. By doing this we were able to build a more precise understanding of the physics of the sound propagation at short range and develop a more precise receivable product for the client.
The collection phase of the project was to be performed in a two-hour window in the early hours of a morning when flow was at a minimum.
To achieve the requirements, SeaView’s team designed and fabricated a custom deployment tool which is essentially a 20′ long linear actuator with an 18ft stroke. SeaView wrote custom control software and integrated a profiling sonar into the system. Both vertical and horizontal accuracy was in the order of 1/16″ over the complete travel distance.
The actuator was held plumb in the surge tower using dedicated guide frames and the tool was actuated up and down a number of times in the two-hour window to build a dense point cloud of the surfaces under investigation.
The sonar data was post processed to produce point cloud images which were in turn converted to Autocad DXF files.