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Time and Model Contracts

Time and model contracts keep navigation science reproducible after data leaves the parser or receiver boundary. Core owns foundational time records. Nav owns GNSS-specific time interpretation, rollover resolution, and the physical models that corrections and estimators depend on.

flowchart LR
    product["navigation product<br/>or observation epoch"]
    time["nav time contracts<br/>system offsets rollover civil UTC"]
    model["nav model contracts<br/>atmosphere antenna tides celestial"]
    correction["corrections"]
    estimator["position PPP RTK<br/>estimators"]

    product --> time
    product --> model
    time --> correction
    model --> correction
    correction --> estimator

Time Surface

surface nav meaning required proof
GnssTimeSystem explicit system identity for GPST, GST, BDT, GLONASS, UTC, and TAI conversion tests
TimeOffsetEvidence source-labelled offset evidence between time systems serialization and conversion tests
TimeConversion<T> converted value plus the evidence used to convert it API and integration tests
UtcCivilTime civil-time parsing and formatting for navigation products leap-second tests
Galileo and BeiDou time records week and time-of-week representation after navigation interpretation broadcast decode tests
GLONASS time records day index and seconds-of-day interpretation GLONASS day-resolution tests
rollover helpers GPS, Galileo, BeiDou week rollover and GLONASS four-year day cycle resolution rollover boundary tests

Model Surface

surface nav meaning consumer
atmosphere and NeQuick models troposphere and ionosphere support used by corrections position, PPP, diagnostics
antenna models receiver and satellite phase-center correction evidence PPP and RTK
celestial models sun and moon support for physical effects tide and phase models
ocean tide loading station displacement support precise positioning
solid earth tide solid-earth displacement support precise positioning

Boundary Decisions

  • Keep generic epoch and serialization meaning in core.
  • Keep parser-local bit extraction in format modules, then hand resolved time evidence to the nav time surface.
  • Keep physical models here only when they support navigation corrections or estimators.
  • Keep repository run layout, artifact placement, and inspection workflows in infra.
  • Treat missing reference-week, reference-day, leap-second, or model-source evidence as a correctness issue, not a presentation issue.

First Proof Check

Inspect navigation-time source, rollover source, model source, the time guide, and model guide. Then inspect focused tests for time-system conversions and troposphere elevation behavior to confirm navigation-specific time interpretation and physical models still match checked scientific proof.