What this SP3 inspector checks
SP3 stores satellite positions and clock offsets at epochs, with optional velocity and clock-rate records. This tool reads the SP3-c/d header, declared satellite list, time system and interval, then counts P and V records per satellite and epoch. It flags count mismatches, duplicates, unlisted satellite records, malformed numeric fields, out-of-order epochs, and gaps against the declared interval.
Missing values and prediction flags
The IGS SP3-d specification uses zero positional components for absent or bad positions and a 999999 clock value for absent or bad clock offsets. P-record columns also carry predicted-orbit, predicted-clock, clock-event, and maneuver flags. These are tallied without interpreting orbit quality or accuracy.
Validation boundary
This is a bounded structural and coverage preflight, not full SP3 conformance or scientific validation. It does not check coordinate frames or GNSS time conversions, decode accuracy/correlation values, interpolate trajectories, validate physical orbit plausibility, or certify a precise ephemeris. It supports SP3-c and SP3-d text records only, not earlier variants or compressed inputs. A clean result means only that these supported checks found no errors.
Frequently asked questions
Does the tool upload my orbit file?
No. Your file is decoded and analyzed locally in your browser; no orbit data is sent to ToolQuill.
What is the difference between an absent P record and a missing position?
An absent P record means no position/clock row was found for a declared satellite at an epoch. A missing position means a P row exists but at least one coordinate is zero, the SP3 missing-value convention.
Why might a good file still show warnings?
An SP3 product can intentionally omit a satellite at some epochs or mark predicted values. The report highlights these cases for review; it does not declare the orbit scientifically invalid.
Authoritative reference
Consult the International GNSS Service SP3-d format specification for record columns, missing-value conventions, and complete format rules.
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