• V. Nagaswapna
• Dr.G.Mamatha

Water vapor is one of the prime elements of the atmosphere that alters its radiation budget directly and also for the fresh water management. But high accuracy with its measurement remains an important challenge. The total column water vapor and precipitation are well associated in the tropics. In this paper, we estimate precipitable water vapor (PWV) by using the observations from Global Navigation Satellite System(GNSS) .The Measurements which we taken from GNSS can be used to sense the atmosphere by measuring the refraction and the delay of the signals as they pass through the atmosphere. From These delays we can infer the column-integrated precipitable water vapor or precipitable water. When a network of GNSS stations is available, they can extensively improve the spatial and temporal coverage of humidity above the surface. Knowing the importance of water vapor Indian Space Research Organization (ISRO) has taken-up a challenging project to get three dimensional profiles of water in all weather conditions. In this regard a network of ground-based GNSS receivers is planning to installed in any one of the station. These receivers collect signals from the GNSS satellites in any direction based on the position of the satellites at that time. Thus the water vapor information obtained from the delay of the signals is total column slant water vapor which is fed to the tomographic technique algorithms to get the 3D water vapor profiles. The efficiency of tomographic methods depends on experimental setup and mathematical algorithms. The retrieval of water vapor profiles depends on the passages of signals in a given voxel .

Global Satellite Navigation System(GNSS), Troposphere water vapor, GPS-tomography.

"Optimal distance estimation for implementing the tomographic technique to retrieve the 3D water vapor profiles from a ground-based GNSS receiver network", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.5, Issue 9, page no.310-317, September-2018, Available :http://www.jetir.org/papers/JETIR1809450.pdf

"Optimal distance estimation for implementing the tomographic technique to retrieve the 3D water vapor profiles from a ground-based GNSS receiver network", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.5, Issue 9, page no. pp310-317, September-2018, Available at : http://www.jetir.org/papers/JETIR1809450.pdf