fix!: consistent nav-data field naming + CNAV-2 EOP ΔUT_GPS scale fix#62
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Resolves #60 and extends it with two further inconsistencies found while auditing all nav-data structs against IS-GPS-200/705/800 and the Galileo OS SIS ICD v2.2. Klobuchar ionospheric coefficients (#60): - GPSL5IData, GPSL1C_DData: α0…α3/β0…β3 -> α_0…α_3/β_0…β_3 Almanac SV-clock coefficients (#60): - GPSL1CAAlmanac: af0/af1 -> a_f0/a_f1 SV health (D): - GPSL1CAData: svhealth -> sv_health, matching the sibling sv_health_sf4_25/ sv_health_sf5_25 fields; IS-GPS-200 labels all of them identically "SV Health". Rate of inclination (E): - GPSL5IData, GPSL1C_DData: i_0_dot -> i_dot. IS-GPS-200/705/800 name this IDOT (an absolute rate, not a delta), matching LNAV/Galileo i_dot; also aligns with PositionVelocityTime.jl's generic data.i_dot access. BREAKING CHANGE: renamed public struct fields on GPSL1CAData, GPSL1CAAlmanac, GPSL5IData and GPSL1C_DData. Downstream code reading the old names must update. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The L1C-D subframe-3 page-2 EOP field was decoded as ΔUT1 = UT1−UTC with scale 2⁻²⁴, reflecting a pre-Rev-G interpretation of the ICD. IS-GPS-800J Table 3.5-5 defines the 31-bit field as ΔUT_GPS = UT1−GPS (UT1−GPST) with scale 2⁻²³ (the rate keeps scale 2⁻²⁵). This brings L1C-D in line with the latest ICD and with the L5 CNAV MT32 decoder, which already uses ΔUT_GPS. - Rename struct/parser field ΔUT1/ΔUT1_dot → ΔUT_GPS/ΔUT_GPS_dot. - Fix scale factor 2⁻²⁴ → 2⁻²³ for the value; rate unchanged. - Update docstring/comments and the SF3 page-2 test expectation. Fixes #61. BREAKING CHANGE: the GPSL1C_DData fields ΔUT1/ΔUT1_dot are renamed to ΔUT_GPS/ΔUT_GPS_dot, and the decoded ΔUT_GPS value is now twice the previous (incorrect) value due to the 2⁻²⁴ → 2⁻²³ scale-factor fix. Downstream code reading data.ΔUT1 must be updated. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The SF3 page-2 EOP assertions previously checked `raw * <the decoder's own LSB>`, which is tautological for scale factors — it cannot detect a wrong scale (this is how the earlier 2⁻²⁴ ΔUT_GPS bug went unnoticed). Re-anchor the EOP fields to Spirent's L1C reference capture: feed the raw integers Spirent actually transmitted and assert the physical values its own reference decoder reported. The expected values now come from an independent decoder, so a scale regression fails the test. Verified: reverting the decoder to 2⁻²⁴ makes the new ΔUT_GPS assertion fail. ΔUT_GPS is asserted as 2× Spirent's printed Delta_UT1, since Spirent uses the pre-Rev-G UT1−UTC scale 2⁻²⁴ while IS-GPS-800J Table 3.5-5 defines ΔUT_GPS = UT1−GPS at 2⁻²³ (matching the L5 MT32 golden test). GGTO stays synthetic — the capture carries no GGTO data — to retain its scale-factor coverage. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Summary
Resolves the field-naming inconsistencies in #60, extends them with two more found
while auditing every nav-data struct against IS-GPS-200/705/800 and the Galileo
OS SIS ICD v2.2, and fixes a CNAV-2 EOP scale-factor bug (#61) that the audit
surfaced. All names/scales are verified against the current ICDs and cross-checked
with GNSS-SDR and RTKLIB/PocketSDR.
Three self-contained commits:
refactor!— unify nav-data field names across signalsfix(l1c_d)!— correct CNAV-2 EOP ΔUT_GPS per IS-GPS-800J (Fixes Wrong LSB scale factor for CNAV-2 (L1C) EOP UT1-GPS difference: 2^-24 should be 2^-23 #61)test(gpsl1c)— anchor the SF3 page-2 EOP test to a Spirent L1C reference capture1. Field-naming unification (breaking)
GPSL5IData,GPSL1C_DDataα0…α3,β0…β3α_0…α_3,β_0…β_3M_0,i_0); aligns withGPSL1CAData(#60)GPSL1CAAlmanacaf0,af1a_f0,a_f1GPSL1CADatasvhealthsv_healthsv_health_sf4_25/_sf5_25; de-gluedGPSL5IData,GPSL1C_DDatai_0_doti_dotIDOT(absolute, not a delta); matches LNAV/Galileoi_dot, GNSS-SDR/RTKLIBidot, andPositionVelocityTime.jl's genericdata.i_dotaccess2. CNAV-2 EOP ΔUT_GPS fix (breaking — value change)
The L1C-D subframe-3 page-2 EOP field was decoded as
ΔUT1(UT1−UTC) with scale2⁻²⁴, a pre-Rev-G reading of the ICD. IS-GPS-800J Table 3.5-5 (and IS-GPS-705JTable 20-VII) define it as
ΔUT_GPS(UT1−GPS) with scale2⁻²³— the rate keeps2⁻²⁵. This brings L1C-D in line with the current ICD and with the already-correctL5 CNAV MT32 decoder.
GPSL1C_DData.ΔUT1/ΔUT1_dot→ΔUT_GPS/ΔUT_GPS_dotΔUT_GPSis now 2× the previous (incorrect) value3. Test hardening
The SF3 page-2 EOP assertions previously checked
raw * <the decoder's own LSB>—tautological for scale factors, which is exactly why the
2⁻²⁴bug went unnoticed.They're now anchored to a Spirent GSS L1C reference capture: the raw integers
Spirent transmitted are fed in, and the assertions are Spirent's own
reference-decoder values (an independent oracle). Confirmed it now catches the bug —
reverting the decoder to
2⁻²⁴makes the test fail.Breaking changes / migration
SemVer-major (public field renames + one value change). Downstream field reads:
Downstream impact checked:
PositionVelocityTime.jlandGNSSReceiver.jlreadnone of the renamed fields — except that PVT's
sat_position.jlalready expectsdata.i_dot, so thei_0_dot → i_dotrename actually aligns the CNAV structswith PVT (no PVT change needed). No consumer reads the EOP fields.
Verification
JuliaFormatter2.8.5: cleanOS SIS ICD v2.2; cross-referenced with GNSS-SDR and RTKLIB/PocketSDR
Release note
This is breaking —
Project.tomlstill reads2.1.0and needs a 3.0.0 bumpbefore tagging (not done in this PR yet).
Closes #60
Fixes #61