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Developing a Coastal Monitoring System For Enhancing Aquaculture Practices
System Collects Atmospheric and Water Data in Near Real Time, Building Models to Optimize Scallop Farming in Chile's Tongoy Bay

Lorenzo Luengo C.
Electrical Engineer
Departamento de Geofísica
Universidad de Concepción
Concepción, Chile

About three kilometers offshore Tongoy, Chile, a town about 360 kilometers north of Santiago, a coastal monitoring system—the first of its kind in the country—provides near-real-time data, with a delay of about 15 minutes after data collection. Similar systems have been previously developed in Chile with little success, and most oceanographic data are collected from moored instruments during cruises only once or twice a year.

The system, which is named Chispita, collects data on several environmental variables, including wind speed and direction, air temperature, humidity, barometric pressure, water temperature, water salinity (conductivity) and dissolved oxygen. Chispita is a part of a research project between the Universidad de Concepción and Centro de Estudios Avanzados en Zonas Áridas (CEAZA). The author completed its programing and integration and also oversaw its deployment with CEAZA marine biologist Ricardo Rodr'guez and other researchers.

Equipment and Technology
Campbell Scientific Inc. (Logan, Utah) provided the monitoring station's atmospheric sensors: It uses a 05106 Wind Monitor-MA, a CS106 barometric pressure sensor and an HMP50 temperature and humidity sensor. For monitoring underwater variables, the system uses a Sea-Bird Electronic Inc. (Bellevue, Washington) SBE16plus V2 CTD sensor.

The system sends data to a computer located in an Invertec Ostimar SA (Vitacura, Chile) facility near the shore using a pair of Campbell Scientific RF401 radio modems, allowing remote data collection and uploading modified configuration files. These radio modems have proved to provide a reliable link, even in heavy fog, at a distance of about seven kilometers with line of sight. At the core of this system, there is a Campbell Scientific CR1000 data logger that integrates all sensors previously mentioned.

The system's location in Tongoy Bay is tagged as 'Balsa Chispita.' The data receiving station is tagged as 'Invertec.' (Image from Google Earth)

The system was mounted and deployed on the Balsa Chispita, a raft owned by a local scallop farming company. The use of this platform drastically reduces the cost of implementation, providing all the buoyancy and structure to support the sensors.

The atmospheric sensors have been mounted on a mast made of galvanized steel that is kept tight by four guy wires. This mast also holds a 10-watt solar panel for charging the system's 12-volt, 7.2-ampere-hour battery, which provides enough energy even on heavily clouded days to keep the system running.

Data Collection
The system has been programmed to collect atmospheric data every 1.5 minutes and water data every 15 minutes. Water sampling occurs less frequently than atmospheric sampling because the energy required to acquire the water data is higher (due to the use of a pump to change the water sample being analyzed by the instrument). Also water variables change slowly enough to be sampled at this rate.

Programming was done with CRBasic, a proprietary language designed specifically for Campbell Scientific data loggers. The advantage of using this language is that most readings from analog sensors can be made using single statements for each one. Only digital sensors that communicate via RS232 protocol required programming.

One problem that needed to be solved was the ability to obtain a correct wind direction measurement. The 05106 Wind Monitor used in the system is designed to be mounted on a fixed mast, but because this system is built on a raft, it is not fixed. As the system moves and rotates depending on the conditions of wind and water current, so does the reference direction.

This problem was overcome by the integration of a 32500 Electronic Compass from R.M. Young Co. (Traverse City, Michigan), the company that also manufactures the 05106 anemometer for Campbell Scientific. This unit reads analog input (voltage and frequency) from the anemometer and digitizes the values. Among the anemometer's operation modes of ASCII output and NMEA, there is a polled mode, which is used for this system. The wind monitor also supports RS485 connections, which are suitable for longer distance and connecting multiple units over a cable. To continue this article please click here.

Lorenzo Luengo C. received his electrical engineering degree in 2009 from the Universidad de Concepción in Chile, where he works at the Department of Geophysics. His research interests are the design of data logging systems and sensor networks.

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