Correction Contracts

Correction contracts are reusable navigation science between observations and solution estimates. They encode physical assumptions: atmosphere, ionosphere, group delay, biases, signal combinations, and carrier effects.

They are public contracts only when more than one solver, product path, or higher-level crate needs the same correction meaning.

Correction Flow

flowchart LR
    obs["observations"]
    products["broadcast or precise products"]
    models["atmosphere and physical models"]
    corrections["correction values"]
    estimator["position, PPP, or RTK estimator"]

    obs --> corrections
    products --> corrections
    models --> corrections
    corrections --> estimator

Contract Families

family	owns	first proof
atmosphere and ionosphere	atmospheric context, broadcast ionosphere, measured ionosphere, residual summaries	the atmosphere model, broadcast residual model, and measured ionosphere model
biases and group delay	code bias, phase bias, broadcast group-delay conversions	the bias model and broadcast group-delay model
combinations	ionosphere-free, geometry-free, narrow-lane, Melbourne-Wubbena, and related combinations	the combination model, ionosphere-free code model, ionosphere-free phase model, and Melbourne-Wubbena model
carrier effects	phase windup and carrier-aware correction helpers	the phase-windup model
dual-frequency support	dual-frequency correction and diagnostic surfaces	the dual-frequency correction model

Boundary Rules

• Navigation owns correction law and model assumptions.
• Signal owns carrier, wavelength, code, raw-IQ, and DSP behavior before navigation correction.
• Core owns shared observation and unit record meaning.
• Receiver owns when a correction is invoked during a runtime pipeline.
• Infra owns persisted product discovery and run evidence around correction use.

Reader Checks

• Which physical assumption changed?
• Which observation, product, or model input is required?
• Does the correction remain reusable across PVT, PPP, RTK, or product validation?
• Does a higher-level failure need correction proof or only receiver/infra handoff proof?

First Proof Check

Start with the navigation correction guide and the correction source tree. Then run or inspect the correction-focused integration tests for ionosphere, windup, bias, and signal-combination behavior before changing correction claims.