Total refractivity fields from GNSS tropospheric delays reconstructed with collocation methods

Abstract

Refractivity of the Earth's troposphere is directly reflected in the observations of space geodesy such as Global Navigation Satellite Systems (GNSS) and satellite radars. Therefore, they can provide valuable information about the quantity and spatio-temporal distribution of atmospheric gases. With improvement of GNSS modeling strategies and increasing network density tomographic approaches were developed. In this paper, we present an alternative tomographic approach based on collocation method to estimate the refractivity field from GNSS observables. Collocation adjustment is used to estimate parameters that relate GNSS observables (such as zenith or slant delays) with refractivities. Therefore, the parameters are used to compute the refractivity field. With this approach, for end-to-end simulations, the refractivity field can be reconstructed with an accuracy of 2.5 ppm and 4.5 ppm in terms of mean and standard deviation respectively; these results are comparable to typical tomography results.