along the beach to quantify the alongshore uniformity of the moveable bed. A
fully automated 3-D bathymetric survey system was developed to minimize the
time and effort required to conduct a bathymetric survey. In addition, the system
needed to be amphibious so that changes to the bathymetry above the still-water
level could be accurately measured.
The system consists of two primary components. First, the vertical elevation
of the sand bed is measured using a commercially available beach profile
indicator consisting of a mechanical spring-wheel system which tracks the
elevation of the bed as the sensor moves along the length of the bridge. Figure 8
shows the profile indicator in a stationary position on the sand bed when the
facility is drained. The spring-wheel assembly is located at the bottom end of the
1.52-m-long vertical rod. As the wheel rolls along the surface of the sand bed at
a constant horizontal speed of 0.1 m/sec, a servomotor maintains a continuous
downward force on the bed equivalent to a mass of 40 g. An analog output
voltage is provided by a potentiometer circuit, which is coupled with the sensor.
This gives a vertical resolution of approximately +1 mm. The sensor has
Previous Page
