Shijo Zacharia

Integrated Navigation System for Remotely Operable Vehicle for 6000m Water Depth

Many underwater positioning techniques have been developed as response to the increase in exploration and exploitation of ocean resources. Though there are many techniques available most successful ones are based on acoustics. Electromagnetic radiation suffers heavy losses in water and can not travel long distance in oceans. Even with the modern navigation equipment like GPS etc. it is not possible to determine the position and track the underwater objects and submersibles without employing subsurface navigational aids. Though techniques such as dead reckoning and inertial navigation are often employed for this propose the cumulative errors are large and for better results periodic correction of the position is required. As the sound is the only radiation that can travel long ranges in oceans underwater Acoustic Positioning Systems have been employed to fix the position of underwater objects and sites and the advent of modern computers Underwater Acoustic Positioning Systems reliable and versatile. However at longer depths acoustic positioning systems alone can not provide the high accuracy and fast update rates. Hence combinations of acoustic and other navigational systems have been recently developed. National Institute of Ocean Technology (NIOT) and Experimental Design Bureau of Oceanological Engineering (EDBOE), Russia have developed an ROV for 6000m (ROSUB 6000) water depths. To meet the challenge of positioning and tracking of the ROV at 6000m depths an Integrated Navigation System combining inertial navigation system and acoustic positioning system with other aids like Doppler velocity log has been developed.

Indigenous drifting buoys for the Indian Ocean observations

Drifting buoys are widely deployed to measure near surface ocean currents and temperature. The Global Ocean Observation System program designed a global array of 1250 drifter buoys to cover oceans at resolution of one per 5 ° × 5 ° grids spatially. The National Institute of Ocean Technology, India indigenized drifting buoy in 2012 with geostationary satellite communication to have near real-time data at every hour. The drifting buoy technology is applied for intellectual property right and transferred to Industries. The measurement scheme in the drifting buoys is capable to measure fluctuations in sea surface temperature and smaller surface eddies. This article describes case studies of indigenous drifting buoys in the Indian Ocean from 2012 onwards. The sea surface temperature and drifting speed measured with indigenous drifting buoy is compared with market available drifting buoy (Marlin-Yug), moored data buoy (BD11) and remote sensed data. We also report results from a drifting buoy with General Packet Radio Service (GPRS) telemetry in the coastal region.

Detection of Buried Objects using active Sonar

An indigenously developed Buried Object Detection SONAR (BODS) for finding targets in the seabed is described in this paper. The important features of BODS are wide bandwidth (2-24 kHz), light weight projector (21 kg) and computer based real time signal processing. The results from experiments at shallow waters to detect seabed boundary layer and targets like metal plate and concrete blocks, are also presented in this paper. It is seen that sediment layers and the targets are distinguishable in the BODS image.

Glider operations in the Bay of Bengal

Indian Ocean has an important role in regional and global climate due to its geography. Presently, variety of ocean observation instruments are employed to measure time and space variability of the large ocean that extends to two closed bays at higher latitudes. Underwater gliders are recently considered to be a vital platform for ocean observation. The revolutionary new underwater glider (“Barathi”), as a mobile sensor node was steered remotely and carried out highly spatial and temporal resolution measurement in Bay of Bengal (BoB) on April-August 2014 is presented in this paper.

Validation methods implemented to ascertain the positional data uncertainty of an indigenously developed drifter buoy-Pradyu

A systematic approach in implementing a suitable validation method which evaluates a newly developed product is highly necessary to ensure its continuous reliability and consistency of its quality[1] performances. More specifically any sensor or instrument developed for the real time data collection and measurement of ocean parameters need to be prejudged and evaluated for its data product quality before its being suggested to use for the practical applications particularly for study and modeling of any physical phenomenon. NIOT has successfully implemented a high accuracy smart sensor GPS receiver module in its drifter buoy which acquires positional (Latitude & Longitude) information and transmits using INSAT modems. NIOT named this drifter buoy indigenization as Pradyu. Performed land based triangulation test method and deployment & comparison of drifters using the imported drifter from Marlin-Yug, Ukraine is carried out in Bay of Bengal. The above validation methods[2] carried out confirms the drifters ability to follow and track the surface mixed layer current[5] with a positional accuracy of ±10m. In this paper, the recent outcome of different methods implemented for validating the drifter is presented.