A new approach for GNSS tomography from a few GNSS stations
Abstract. The determination of the distribution of water vapor in the atmosphere plays
an important role in the atmospheric monitoring. Global Navigation Satellite
Systems (GNSS) tomography can be used to construct 3-D distribution of water
vapor over the field covered by a GNSS network with high temporal and spatial
resolutions. In current tomographic approaches, a pre-set fixed rectangular
field that roughly covers the area of the distribution of the GNSS signals on
the top plane of the tomographic field is commonly used for all tomographic
epochs. Due to too many unknown parameters needing to be estimated, the
accuracy of the tomographic solution degrades. Another issue of these
approaches is their unsuitability for GNSS networks with a low number of stations, as
the shape of the field covered by the GNSS signals is, in fact, roughly that of an
upside-down cone rather than the rectangular cube as the pre-set. In this
study, a new approach for determination of tomographic fields fitting the
real distribution of GNSS signals on different tomographic planes at
different tomographic epochs and also for discretization of the tomographic
fields based on the perimeter of the tomographic boundary on the plane and
meshing techniques is proposed. The new approach was tested using three
stations from the Hong Kong GNSS network and validated by comparing the
tomographic results against radiosonde data from King's Park Meteorological
Station (HKKP) during the one month period of May 2015. Results indicated
that the new approach is feasible for a three-station GNSS network
tomography. This is significant due to the fact that the conventional
approaches cannot even solve a network tomography from a few stations.