Abstract
Introducing ionospheric information into a precise point positioning (PPP) solution enables faster ambiguity resolution and significantly improves positioning accuracy. To compute such corrections over wide areas, sparse networks with potentially irregular station distributions are often used. This aspect brings a new level of complexity as ionospheric corrections should be weighted appropriately in the PPP filter. This paper presents a possible implementation of grid-based wide-area slant ionospheric delay corrections, with a focus on the reported uncertainties. A balance is obtained between obtaining corrections with formal errors small enough to enable fast convergence, while large enough to overbound most errors. Based on least-squares collocation, the method uses satellite-specific variograms based on the 99th percentile values in each distance bin. Tested in southern Canada over a 53-week period in 2020, ionospheric grids allowed dual-frequency receivers to obtain around 5 cm accuracy in each horizontal component within 5 min of static data collection. For single-frequency solutions using data from geodetic receivers, positioning errors were reduced by over 60% for both static and kinematic processing.
Highlights
Dual- frequency global navigation satellite system (GNSS) receivers can precisely measure ionospheric delays due to the dispersive properties of the medium for radio waves
This paper provides a possible implementation of wide-area grid-based slant ionospheric delay corrections and its application to precise point positioning (PPP)-RTK, describing the computation of precise slant ionospheric delays at individual stations, the functional and stochastic models for ionosphere modeling, the creation of satellite-specific grids, and the ingestion of gridded corrections at the user end
All but six belong to two stations. The cause of these larger RMS errors was traced to the presence of small (1 cycle) undetected cycle slips: while they are partly absorbed by ionospheric parameters in the solution without grids, the tighter constraints provided by the external ionospheric corrections seem to push the errors into the position estimates
Summary
Dual- (or multi-) frequency global navigation satellite system (GNSS) receivers can precisely measure ionospheric delays due to the dispersive properties of the medium for radio waves. This paper provides a possible implementation of wide-area grid-based slant ionospheric delay corrections and its application to PPP-RTK, describing the computation of precise slant ionospheric delays at individual stations, the functional and stochastic models for ionosphere modeling, the creation of satellite-specific grids, and the ingestion of gridded corrections at the user end. An assessment of these grids in the positioning domain is conducted
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