How to read a RINEX quality report: gaps, slips, multipath and SNR
Read a RINEX quality report in this order: session coverage, observation availability, phase continuity, multipath and signal strength, then antenna and station metadata. Compare metrics for the same signals and elevation mask. A good QC score indicates usable observations; it does not establish coordinate accuracy.
Separate missing epochs from missing observations
Epoch completeness describes the presence of timestamps. Observation completeness describes the measurements available within those timestamps, using the denominator defined by the QC tool. A receiver can log continuously while losing several satellites or one frequency. Read both measures and inspect the per-satellite plots.
| Worked example | Calculation |
|---|---|
| An inclusive one-hour grid, from 00:00:00 through 01:00:00 at 30 seconds | 3,600 / 30 + 1 = 121 expected epochs |
| The file contains 115 of those epochs | 115 / 121 × 100 = 95.04% epoch completeness |
| Why another report may differ | Its interval may exclude the final endpoint or use a different expected observation window |
Interpret cycle slips as interruptions of phase continuity
A cycle slip is a discontinuity in the accumulated carrier-phase measurement. Loss of lock, obstruction and receiver behaviour can contribute. Different detection methods use different combinations of observables, so slip counts from two engines are not automatically interchangeable.
- Check whether events affect one satellite or many satellites at the same epoch.
- Compare rates over a stated denominator, such as epochs, observations or satellite arcs; retain the raw count too.
- Inspect low-elevation arcs and the field log before deciding that an event indicates faulty equipment.
- Do not remove every flagged epoch blindly. Review whether the processing engine can restart or repair the affected ambiguity arc.
MP1 and MP2 are diagnostics, not position errors
Code multipath combinations use code and carrier observations to reduce some common effects and expose multipath and measurement noise. Their statistics depend on signals, arc handling and filtering. A reported multipath value in metres is not the horizontal error of the final coordinate, and a universal pass threshold is inappropriate for every receiver and environment.
- Compare the same station, signal and elevation range across sessions.
- Look for repeatable satellite-direction patterns near reflective surfaces.
- Distinguish a gradual change at one station from a change introduced by a new QC engine or configuration.
Check signal-strength units before comparing numbers
GNSS software sometimes labels carrier-to-noise-density ratio as SNR. RINEX may carry signal-strength observations and compact strength indicators, which are different fields. Inspect the header, receiver documentation and report definition before interpreting a number as dB-Hz. Compare signal strength with satellite elevation and with the same equipment settings.
Sources: IGS: formats and standards
Turn a report into a field decision
| Pattern | Next check |
|---|---|
| All satellites disappear together | Power, recorder interruptions, file truncation and clock events |
| One signal is consistently absent | Receiver tracking configuration and converter signal mapping |
| Low-elevation arcs are weak and interrupted | Sky obstruction, elevation mask and antenna surroundings |
| QC looks good but coordinates disagree | Antenna height, base coordinates, reference frame, epoch and processing products |
References and methodology
Technical definitions follow the sources below. Worked examples are illustrative; product-specific thresholds are identified as PosFlow settings. For corrections, contact PosFlow with the article URL and the relevant specification.