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Original Indiana Prototype Tethered ADCP Platform

The basic premise of the tethered-platform method consists of a lightweight floating platform for an attached ADCP that can be pulled manually across a river to make a discharge measurement.

Making a discharge measurement.  

Making a discharge measurement with the original prototype platform.
Click for larger image

The original prototype tethered platform had a catamaran configuration and was constructed of polystyrene-foam floats built from a composite of several layers of 2-inch-thick standard insulation cut into a semi-vee shape.
Bottom view of polystyrene-foam floats and ADCP.  

Bottom view of polystyrene-foam floats and ADCP.
Click for larger image

The ADCP tethered-platform needed telemetry capability with a computer stationed on shore. This was accomplished by using two 900-megahertz (MHz) radio modems, one on the tethered boat connected to the ADCP and the other on the bank connected to a Pentium laptop computer that ran the software and collected  data from the measurement. The modems were not waterproof and needed to be housed with the battery in the NEMA enclosure. A 7.5-amp gel-cell battery that operated the ADCP and the modem lasted for about three measurements. The weight of the original prototype was about 40 pounds in measurement-ready condition.

 

Recording the data.  

Recording the data, using radio-modem telemetry.
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To make a discharge measurement, the  tethered platform was lowered into the water from a bridge and then guided across the stream by a rope tether. The design emphasis was on speed and ease of use. The boat was hand carried to the bridge or cableway where it was deployed over the guardrail into the stream. Once in the water, the boat was walked through a practice traverse or to a starting edge. When the operator of the computer was ready, a signal was given to the boat operator to begin a traverse (a single traverse across the river with an ADCP, resulting in one measurement of discharge, is called a "transect"). All measurements were made according to quality-assurance procedures published in "Quality-Assurance Plan for Discharge Measurements using Broadband Acoustic Doppler Current Profilers," (USGS Open File Report 95-701). The Indiana District office built several tethered platforms similar to the original for other USGS district offices.  The Indiana District office continues to use the original prototype platform to make discharge measurements.

In 1999, the Indiana District office started working on a new project to refine this prototype tethered platform. The project is part of a joint effort by the Indiana and Kentucky District offices for the USGS Instrument Committee and Office of Surface Water. The Indiana District office is refining the tethered platform, and the Kentucky District office is refining the remote-controlled platform developed in that office. 

The major objectives of the project are to:

 Results of the tethered-platform part of the project can be found here.

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U.S. Department of the Interior
U.S. Geological Survey
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URL: http://sunrise.er.usgs.gov/hydroacoustics/originaltetheredplatform.shtml
Last modified:Monday, 13-Aug-2007 15:58:46 EDT
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