text: Accuracy The Standard Positioning Service system is intended to provide an absolute position accuracy of about 5 to 10 metres throughout the Indian landmass and an accuracy of about  in the Indian Ocean as well as a region extending approximately  around India. GPS, for comparison, has a position accuracy of 5 m under ideal conditions. However, unlike GPS, which is dependent only on L-band, NavIC has dual frequencies (S and L bands). When a low-frequency signal travels through atmosphere, its velocity changes due to atmospheric disturbances. GPS depends on an atmospheric model to assess frequency error, and it has to update this model from time to time to assess the exact error. In NavIC, the actual delay is assessed by measuring the difference in delay of the two frequencies (S and L bands). Therefore, NavIC is not dependent on any model to find the frequency error and can be more accurate than GPS.
  Clock failure
  In 2017, it was announced that all three SpectraTime supplied rubidium atomic clocks on board IRNSS-1A had failed, mirroring similar failures in the European Union's Galileo constellation. The first failure occurred in July 2016, followed soon after by the two other clocks on IRNSS-1A. This rendered the satellite non-functional and required replacement. ISRO reported it had replaced the atomic clocks in the two standby satellites, IRNSS-1H and IRNSS-1I in June 2017. The subsequent launch of IRNSS-1H, as a replacement for IRNSS-1A, was unsuccessful when PSLV-C39 mission failed on 31 August 2017. The second standby satellite, IRNSS-1I, was successfully placed into orbit on 12 April 2018.
  In July 2017, it was reported that two more clocks in the navigational system had also started showing signs of abnormality, thereby taking the total number of failed clocks to five, in May 2018 a failure of a further 4 clocks was reported, taking the count to 9 of the 24 in orbit.
  As a precaution to extend the operational life of navigation satellite, ISRO is running only one rubidium atomic clock instead of two in the remaining satellites.