Exploration and exploitation of the marine resources, both living and non-living, is unthinkable without acoustic instruments. With this background and in view of India's vast coastline and EEZ, the Marine Instrumentation mission of the National Institute of Ocean Technology has been geared towards development of acoustic based instruments along with other specialised instruments.

11.4.1 Design and Development of Acoustic Tide Gauge (ATG)

An Acoustic Tide Gauge (ATG) was designed and developed with an accuracy of better than 1 cm, and field trials were conducted at Chennai Port Trust. The complete system is being re-engineered to suit the marine environment.

ATG analog electronic hardware components have been built in-house. Dedicated signal processing system have been developed. The whole system has been designed as a stand-alone system and can hold one month's tide data. This data can be downloaded to a laptop or a desktop computer through a serial port.A novel calibration technique using quarter wave tubes as side branches has also been developed by NIOT to minimize errors due to temperature effects. This version has a high signal to noise ratio.

Field trials of the first prototype of ATG took place at Chennai Port during November, 1997. The data collected using the ATG by NIOT has been verified with that collected by using a mechanical tide gauge. The agreement between both the data collected is very good. The prototype II with improved features under development.

11.4.2 Remotely Operable Sea Skimmer (ROSS)

The objective of the project was to design, develop and fabricate a prototype ROSS module with environmental sensor and under radio control from a stationery ship or shore. This will enable rapid acquisition of biological and physical variables that are commonly measured in oceanography. The National Institute of Oceanography (NIO), Goa was entrusted with the task of developing the concept, mission software, erc. The Indian Institute of Technology, Chennai, was entrusted with the task of development of a stable, unsinkable hull. The full scale hull module has been tested for its hydrodynamic properties. A joystick controller has also been tested . A GPS card for finding out the position of the platform has been acquired and is being integrated into the system. The mission software is also being developed and tested.

11.4.3 Technology Development for Multilayer Current Measurement

A 3-component multilayer Perforated Ball Velocity Meter (PVBM) has been developed. This will be useful in collecting information about wave currents and water particle kinematics. Ten strain gauge cantilever arms with perforated balls, which form the main component of PVBM current meter, have been fabricated and tested in laboratory. Software to compute velocities from the measured forces was also developed and tested. The laboratory model has been demonstrated at the wave basin in September, 1997. The project has been completed in March'98 with the realisation of a spare unit and to formulate a proposal for a hand held portable velocity meter for field use.