Jai G Singla, Sunanda Trivedi

GNSS observations are carried out in static mode/ Differential global navigation satellite
system (DGNSS) and dynamic mode / Real time Kinematics (RTK) mainly. RTK mode of
observation is useful in case of navigation whereas in order to determine very precise
positioning, static / DGNSS/ DGPS mode is recommended. In this study, we have examined
the quality of DGNSS survey of an urban city in India over ~300 Ground Control Points. Survey
is carried out in DGNSS mode with dual frequency mode. All the observations were recorded
using GPS, GLONASS , Galileo and Beidu with GDOP values in the range of 1.4 to 2.5. Beidu
was used in broadcast ephemeris mode whereas for other constellations, precise orbit
ephemeris were obtained from International GNSS service (IGS) site as per the observation
day and month. Further, all the data was post processed in the SW suite and positional and
vertical accuracies of millimeter to few centimeter level were obtained. This paper describes
the approach of Ground Control Point (GCP) identification, surveying, methodology, use of
CORS network and data post-processing in order to achieve such a precise accuracies in the
urban city.