ISRO's PSLV-C33, carrying India's seventh navigation satellite IRNSS-1G, blasted off from the Satish Dhawan Space Centre in Sriharikota at 12.50pm on Thursday. 
The countdown for the launch of the 1,425-kg satellite, IRNSS-1G, began at 9.20am on Tuesday. The integration of the rocket on the launch pad and the propellant filling operations were taken up at different stages during the 51.30-hours countdown. 
A regional navigation satellite system with just seven spacecraft and in civil domain is unique to India. The three global versions of other countries offer worldwide commercial coverage and are operated by their respective militaries. 
IRNSS will be to the subcontinent what the GPS is to its users worldwide, but with far greater precision and in Indian control, according to the Indian Space Research Organisation. It is expected to provide position accuracy of better than 20 m over Indian region and also an area extending up to 1,500 sq. km around India. 
The well-known GPS is owned by the U.S. Air Force; Russia has GLONASS and China is expanding its regional BeiDou into a global system, also operated by its military. Europe’s GALILEO is a civil global system. They each have between 28 and 35 satellites. 
IRNSS will drive both everyday uses as a 24/7 standard service for air, sea, ship transport among others. It will also be used for military and missile-related applications as an encrypted and restricted service. 
Over the next three to six months, all the IRNSS satellites would be stabilised as a constellation, their signals and performance verified and later put to use, an ISRO official had said. 
The constellation has been in the making since July 2013 when IRNSS-1A, was launched. ISRO placed IRNSS-1E and IRNSS-1F in January and March this year, each with a designed life of 12 years.