Bounding higher‐order ionosphere errors for the dual‐frequency GPS user

Abstract

[1] Civil signals at L2 and L5 frequencies herald a new phase of Global Positioning System (GPS) performance. Dual-frequency users typically assume a first-order approximation of the ionosphere index of refraction, combining the GPS observables to eliminate most of the ranging delay, on the order of meters, introduced into the pseudoranges. This paper estimates the higher-order group and phase errors that occur from assuming the ordinary first-order dual-frequency ionosphere model using data from the Federal Aviation Administration's Wide Area Augmentation System (WAAS) network on a solar maximum quiet day and an extremely stormy day postsolar maximum. We find that during active periods, when ionospheric storms may introduce slant range delays at L1 as high as 100 m, the higher-order group errors in the L1-L2 or L1-L5 dual-frequency combination can be tens of centimeters. The group and phase errors are no longer equal and opposite, so these errors accumulate in carrier smoothing of the dualfrequency code observable. We show the errors in the carrier-smoothed code are due to higher-order group errors and, to a lesser extent, to higher-order phase rate errors. For many applications, this residual error is sufficiently small as to be neglected. However, such errors can impact geodetic applications as well as the error budgets of GPS Augmentation Systems providing Category III precision approach.

Assessment of second‐order ionosphere error in GPS range observables using Arecibo incoherent scatter radar measurements

“…The two key parameters required to compute the error are the electron density distributions and the projection of the Earth's geomagnetic field onto the satellite signal propagation direction along the signal path. Theoretical and modeling studies have shown that for dual frequency receivers, higher‐order ionospheric error residuals could reach up to ∼10 cm during geomagnetic storms, but should remain less than 1∼2 cm under quiet conditions [ Bassiri and Hajj , 1993; Brunner and Gu , 1991; Datta‐Barua et al , 2008; Kedar et al , 2003]. These works used simplified ionospheric electron density distributions and geomagnetic fields to derive their results.…”

“…Bassiri and Hajj [1993] modeled the ionosphere as the sum of three Chapman layers, each with a different scale height, peak layer height, and peak layer electron density. Datta‐Barua et al [2008] and Kedar et al [2003] approximated the ionosphere as a uniformly distributed thin layer located at a fixed altitude of 350 km and 400 km, respectively. Hoque and Jakowski [2008] used a combination of three Chapman layers to describe the F2, F1, and E layers and an exponential decay function to describe the plasmasphere above 1000 km altitude.…”

Ionospheric Propagation Effects on GNSS Signals and New Correction Approaches

“…Brunner & Gu (1991) were pioneers to compute higher order ionospheric effects and developing correction for them. Since then higher order ionospheric effects have been studied by different authors during last decades, e.g., Bassiri & Hajj (1993), Jakowski et al (1994), Strangeways & Ioannides (2002), Kedar et al (2003), Fritsche et al (2005), Hawarey et al (2005), Hoque & Jakowski (2006, 2010b, Hernández-Pajares et al (2007), Kim & Tinin (2007, Datta-Barua et al (2008), Morton et al (2009), Moore & Morton (2011). The above literature review shows that higher order ionospheric terms are less than 1% of the first order term at GNSS frequencies.…”

Ionospheric Anomalies During the March 2013 Geomagnetic Storm from BeiDou Navigation Satellite System (BDS) Observations

“…Based on the thin shell ionosphere assumption, TEC can be converted to vertical TEC using the simple cosine mapping function as follow [15]:…”