Bathymetry is the measurement of the depths of water bodies from the water surface. The vast majority of the bathymetric surveys we have conducted within the ponds and canals of the area have been done with a rowboat, a prism mounted atop a long pole with a large plat on the bottom which will not sink into the silt or puff mud, and a total station set up on shore. This simple methodology gets the job done and eliminates the need for the reduction of the sounding data and corrections for tides.
For larger bathymetric surveys our staff have used transducers which transmit a sound pulse from the boat and which records the signal when it bounces from the bottom of the water body. The echo sounder attached to the transducer filters and records the travel time of the pulse. At the same time that the pulse occurs, a GPS unit records the location of the reading. After many of these readings are taken, corrections are made based on fluctuations in the water surface elevation that may have occurred during the survey. The individual points are then mapped.