Linear combinations of GNSS phase observables to improve and assess TEC estimation precision
Date
2017
Authors
Breitsch, Brian W., author
Morton, Jade, advisor
Rino, Charles, committee member
Betten, Anton, committee member
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Abstract
One of the principal observations derived from GNSS (Global Navigation Satellite Systems) signals is ionospheric total electron content (TEC), which is a measure of the density of free electrons (i.e. ionosphere plasma density) integrated along the signal path. TEC is typically computed using the difference of dual-frequency signals from a GNSS satellite, thereby taking advantage of the frequency dispersive effects of ionosphere plasma on microwave-band propagation. However, it is difficult to distinguish between the ionosphere and other frequency-dependent effects, such as multipath and satellite antenna phase effects. Newly available triple-frequency GNSS signals allow computation of geometry-ionosphere-free combinations (GIFC) that specifically highlight the impact of residual errors from these effects. This work aims to: 1) introduce a framework for choosing linear estimator coefficients for GNSS parameters, 2) use this system to derive triple-frequency TEC estimator and GIFC coefficients, 3) introduce and summarize typical GIFC signals from real triple-frequency GPS data, 4) highlight the various frequency-dispersive effects that pervade these signals, and 5) use statistics from GIFC signals to assess the impact of error residuals on TEC estimates made using GPS signals.
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Subject
ionosphere
precision
GNSS
TEC
linear estimation