Module delta 

Reading a Signal K delta, in the units the rest of this workspace uses.

The wire is SI and the rest of this workspace is not: Signal K carries courses and headings in radians and speeds in metres per second, while everything above nav-math works in degrees and knots. Position is the exception – it is already degrees. That conversion happens here, once, rather than in every consumer, and it is the main thing this module is for.

Anything unrecognised is skipped rather than refused. A Signal K server sends dozens of paths a caller may have no use for and will send more after the next update; a reader that failed on the first unknown one would stop working the day the boat gained a sensor.

Structs

Delta

One delta message, read.

Depth

A sounding, and what it was measured from.

Offsets

The vessel’s sounder geometry, as far as it is known.

Reading

One value from one source.

Enums

AisClass

Which kind of AIS transponder a target carries, sensors.ais.class.

AisTargetStatus

The tracking status a target-tracking plugin publishes per target on sensors.ais.status – confirmed live against sk-ais-status-plugin (not a Signal K specification path, a third-party convention). Its own README recommends the following treatment:

Context

Whose data a delta is about.

Measurement

The values a caller has a use for. Everything else on the wire is skipped.

NotificationSeverity

A Signal K notification’s own severity – the schema’s alarmState enum, read off a notification’s state field. Five of its six defined values are modelled here (nominal is left out: the schema defines it, but no producer this crate has actually been read against – neither signalk-derived-data nor signalk-ais-target-prioritizer’s own CPA alarms, both confirmed live – ever emits it, and the same skip-unrecognised discipline this module keeps everywhere else means an unmodelled value is simply not a reading rather than a parse failure).

Sounding

What a sounding is measured from.

Functions

parse

Reads one delta message.