Abstract
In this manuscript, we introduce the Ionospheric Tomographic Common Clock (ITCC) model of undifferenced uncombined GNSS measurements. It is intended for improving the Wide Area precise positioning in a consistent and simple way in the multi-GNSS context, and without the need of external precise real-time products. This is the case, in particular, of the satellite clocks, which are estimated at the Wide Area GNSS network Central Processing Facility (CPF) referred to the reference receiver one; and the precise realtime ionospheric corrections, simultaneously computed under a voxel-based tomographic model with satellite clocks and other geodetic unknowns, from the uncombined and undifferenced pseudoranges and carrier phase measurements at the CPF from the Wide Area GNSS network area. The model, without fixing the carrier phase ambiguities for the time being (just constraining them by the simultaneous solution of both ionospheric and geometric components of the uncombined GNSS model), has been successfully applied and assessed against previous precise positioning techniques. This has been done by emulating real-time conditions for Wide Area GPS users during 2018 in Poland.
Highlights
In this paper we introduce the Ionospheric Tomographic Common Clock (ITCC) model of undifferenced uncombined GNSS measurements
In particular, the precise positioning service in Wide Area networks based on undifferenced and uncombined modelling, which is specially suitable for multi-GNSS and multifrequency signals, due to its sim
TOMION v1 was initially designed for solving ionospheric tomographic models based on dual-frequency GPS measurements and for generating Global Ionospheric Maps, [9,10]
Summary
In this paper we introduce the Ionospheric Tomographic Common Clock (ITCC) model of undifferenced uncombined GNSS measurements. TOMION v1 was initially designed for solving ionospheric tomographic models based on dual-frequency GPS measurements and for generating Global Ionospheric Maps, [9,10] Afterwards, this ionospheric model was further developed and synergistically connected with a precise GNSS non-frequency-dependent terms model, which was able to estimate position, clock errors and zenith tropospheric delay: TOMION v2. By not combining GNSS data in time and/or in frequency, the UU estimables are less noisy when stochastic methods are used to solve the GNSS equations Combined methods, such as standard PPP, remove almost all the ionospheric delay, which turns out to be a bottleneck for the convergence time of the ambiguities, up to the point that it may take an hour to achieve cm-level accuracy.
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