Glass RPC detector R&D for a mega neutrino detector

India-based Neutrino Observatory (INO) collaboration has proposed a 50 kTons magnetised iron calorimeter (ICAL), whose primary goals are to precisely determine oscillation parameters of the atmospheric neutrinos, to study matter effects on the oscillations and finally to use it as a long baseline detector for the neutrino beams. Good tracking and energy resolutions, good directionality (translating to a time resolution of better than a ns) and charge identification of the detecting particles are the essential requirements of ICAL detector. The ICAL detector will cover an area of about 100,000 m² and will use about 30,000 glass Resistive Plate Chambers (RPCs) of about 2 m × 2 m in area as active detector elements. An aggressive R&D program to develop and characterise RPCs operating in the avalanche mode was undertaken. We will describe our R&D efforts towards developing these devices and will present the results of their characterisation studies.