PlanObject

Source file	schemas/plan_object.schema.json
$id	urn:synapsecommand:cdm:3.0.0:plan_object
CDM schema version	3.0.0
SHA-256 of source	fec19733e1521067754ec1a1ec920698636c9133450c54b80b5d14fa0d832e94

What we push OUT: a drawing a commander's plan puts on someone else's map.

Geometry is REQUIRED here, unlike on Event. An overlay with no geometry cannot be drawn, so an egress adapter would have to either invent a location or silently drop the object — and a COA sketch that quietly fails to appear on the TAK client is the worst of the three outcomes, because everyone assumes it arrived.

Fields

Field	Type	Required	Description
area	Area | null	no	Lateral geometry with vertical limits and time validity, when this object is a region. geometry above stays the required projection of its lateral extent. Default null.
expires_at	string | null	no	When the drawing should disappear. None = until explicitly removed — which for a stale COA sketch on a live map is a decision, so state it. KEPT beside validity below, of which it is the projection: a receiving client that only knows how to expire an overlay reads this one field. Default null. (pattern ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}Z$)
geometry	Point | LineString | Polygon | MultiPoint | MultiLineString | MultiPolygon	yes	GeoJSON, WGS84, [lon, lat] order. Required.
integrity	Integrity | null	no	PQC signature block — designed, not yet populated. A DATA CONTAINER and nothing more: this package makes no signature and verifies none, no conformance check, harness column or evidence field reads it, and its presence on an object proves nothing about the object. A record carrying one is unverified until something outside this package verifies it. Default null.
label	string | null	no	What a client shows next to the drawing. None = unlabelled; never an empty string, which renders as a blank callout. Default null. (min length 1)
object_id	string (uuid)	yes
object_kind	"plan_object"	no
object_type	ObjectType	yes
quality	Quality | null	no	How good the SOURCE says this object is. None = the source said nothing about quality, which is not the same as saying it is poor. Default null.
residual	Residual | null	no	Source information the CDM does not model, under the name of the format it came from (§28). None = nothing was left over, or — for the fourteen adapters shipped before this container existed — the leftovers are parked in attributes / payload under source_extras, which ARCHITECTURE.md §5 rules they keep through Part 1. Default null.
route	Route | null	no	Ordered waypoints and legs, when this object IS a route (ObjectType.ROUTE). geometry above stays REQUIRED and stays the LineString projection of the waypoints, so every consumer written before routes existed still draws it. Default null.
schema_version	string	no	Semver of the CDM this object was written against. Default "3.0.0". (pattern ^(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)$)
source	SourceRef	yes	Which adapter produced this object. Required on every kind.
source_ids	array<SourceId>	yes	Every external identifier this object is known by. At least one, on EVERY kind — see the class docstring. (min items 1)
status	OperationalStatus | null	no	The source's own operational state for this object, namespaced. None = the source stated none. Default null.
style	object	no	Rendering HINTS, not requirements — stroke, fill, opacity, dash. A receiving client is free to ignore them, so nothing that changes MEANING may live here (an affiliation belongs on the entity, not in a colour).
validity	TemporalValidity | null	no	The four times the source states about this object (§27). expires_at above is the projection of validity.valid_to for clients that read one field; when both are stated they must agree. Default null.

additionalProperties: false

Unknown keys are rejected. That is safe only because the CDM pairs strictness with a declared escape hatch — Entity.attributes and Event.payload accept anything — so an adapter never has to choose between dropping a field and failing validation.

Referenced definitions

Every $ref on this page resolves to one of these, inlined here so the page is a complete reference and not a starting point for chasing pointers.

Area

A region with lateral geometry, optional vertical limits and optional time validity.

The three together are what an airspace, a danger area, a jamming footprint and a search box all are, and the reason they are one model is that any two of them without the third is a different claim: a polygon with no ceiling is the whole column of sky above it, and a polygon with no validity is permanent.

geometry is a Polygon or a MultiPolygon and nothing else. A point or a line is not an area — a corridor drawn as a line has no width, and a consumer that buffered it would be choosing the width itself, which is an operational decision an adapter may not make (Rule 6).

Field	Type	Required	Description
bounds	BoundingBox | null	no	The coarse extent the SOURCE declared about this area, when it declared one. NEVER computed from geometry here: a sensor's declared coverage rectangle and its footprint's envelope are different facts and are allowed to differ, so a computed value would overwrite one with the other. Default null.
geometry	Polygon | MultiPolygon	yes	Lateral extent. WGS84, [lon, lat].
validity	TemporalValidity | null	no	When the area applies. None = the source stated no times. Default null.
vertical	VerticalExtent | null	no	Floor and ceiling. None = the source stated no vertical limits, which is not the same as surface-to-unlimited (that is a VerticalExtent with both bounds absent, and it says the source described the column). Default null.

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

BoundingBox

A rectangular region in WGS84, bounds NAMED rather than positional.

Why not RFC 7946 §5's bbox array: it is [west, south, east, north] and nothing in a four-float array stops a reader from taking it as [south, west, north, east]. That transposed reading is legal for most of the globe and puts the box in the wrong hemisphere, which is the same silent defect _check_lonlat exists to catch and cannot catch inside an array of four. Named fields make it unspellable. An adapter that must emit RFC 7946's array builds it from these four, in that order, at the edge where it is writing GeoJSON anyway.

A box is not a Polygon and is not a substitute for one. It is the coarse extent a source states about itself — a coverage envelope, a search area, a tile — and a consumer that draws it as a shape is drawing something the source did not describe. Where the source really does describe a region, that region is a Polygon or a MultiPolygon.

Field	Type	Required	Description
max_lat	number	yes	North edge, WGS84 degrees. (≥ -90; ≤ 90)
max_lon	number	yes	East edge, WGS84 degrees. (≥ -180; ≤ 180)
min_lat	number	yes	South edge, WGS84 degrees. (≥ -90; ≤ 90)
min_lon	number	yes	West edge, WGS84 degrees. (≥ -180; ≤ 180)
vertical	VerticalExtent | null	no	Floor and ceiling, when the source states a volume. Default null.

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

Integrity

DESIGNED, NOT IMPLEMENTED — the field the PQC signature will occupy.

No crypto happens in this package (tests/test_cdm_boundary.py asserts the package imports no crypto module). The field exists from day one so that turning signing on is a value change rather than a schema change: a schema change would be a MAJOR bump rippling through every store and every consumer, and would arrive exactly when the signing work is already late.

algorithm is a free string rather than an enum, naming what the platform's ledger already uses — ML-DSA-87 for entry signatures, SLH-DSA for checkpoints. Free, because the algorithm that replaces those is not knowable now, and an enum would make the migration a MAJOR bump for a value nobody reasons over programmatically.

All three fields or none. A block holding a signature with no algorithm is unverifiable, and an unverifiable signature that LOOKS present is worse than an absent one: it reads as assurance to everything downstream that does not check.

Field	Type	Required	Description
algorithm	string	yes	e.g. ML-DSA-87, SLH-DSA-SHAKE-256s. (min length 1)
chain_hash	string	yes	Hash binding this object to the chain. (min length 1)
signature	string	yes	(min length 1)

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

LineString

Field	Type	Required	Description
coordinates	array<array<number>>	yes	(min items 2)
type	"LineString"	no

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

MultiLineString

Several lines that are one thing — a route with a gap, a corridor in two legs.

Field	Type	Required	Description
coordinates	array<array<array<number>>>	yes	(min items 1)
type	"MultiLineString"	no

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

MultiPoint

Several points that are ONE thing — a scatter of detections from one report.

Not a list of Point objects, because a list of geometries is a list of objects and this is one object with a discontinuous location. The difference is visible the moment a consumer counts contacts.

Field	Type	Required	Description
coordinates	array<array<number>>	yes	(min items 1)
type	"MultiPoint"	no

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

MultiPolygon

Several polygons that are one thing — an airspace in disjoint lateral parts.

The ring rules are Polygon's and are enforced per part, for the reason they are enforced there: a ring that arrives open is a source or adapter defect, and closing it invents an edge the source never stated.

Field	Type	Required	Description
coordinates	array<array<array<array<number>>>>	yes	(min items 1)
type	"MultiPolygon"	no

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

ObjectType

What we push OUT — the egress direction, e.g. to TAK as a drawing object.

Closed vocabulary — a value outside this list is invalid, and UNKNOWN is a

member rather than a null wherever the enum has one.

Value
COA_SKETCH
ROUTE
CONTROL_MEASURE
ANNOTATION

OperationalStatus

What state the source says a thing is in, in the SOURCE's vocabulary, namespaced.

THERE IS NO ENUM HERE AND THERE WILL NOT BE ONE. "SERVICEABLE", "DEGRADED", "MISSION CAPABLE", "RED" and "U/S" come from five different domains and mean five different things, and a closed CDM vocabulary would have to map each of them onto a member — which is a judgement about somebody else's operational language, made inside a translator, invisible in the output, and exactly what Rule 6 forbids. namespace says whose vocabulary state belongs to, so a consumer meeting an unfamiliar value can find out what it means instead of guessing; a consumer MUST NOT compare state across namespaces.

since is when the state began, not when it was reported. Absent means the source did not say — never the receipt time, which would make every restart look like a state change.

Field	Type	Required	Description
attributes	object	no	Status-specific source fields with no canonical home.
namespace	string	yes	Whose vocabulary state is in — normally the source format's name. Required: an unnamespaced status is a word with no owner. (min length 1)
since	string | null	no	When the state began. None = the source did not say. Default null. (pattern ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}Z$)
state	string	yes	The source's own token, verbatim and untranslated. (min length 1)

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

Period

A closed or open-ended interval. start required, end optional and open-ended if absent.

start is required and end is not, because that asymmetry is what the sources state: an activation begins at a stated instant and ends "until further notice" far more often than the reverse. An interval with neither bound is not a period, it is the absence of one, and the field holding a Period is optional for exactly that case.

Field	Type	Required	Description
end	string | null	no	When it closes. None = open-ended, never 'unknown'. Default null. (pattern ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}Z$)
start	string	yes	When the interval opens. (pattern ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}Z$)

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

Point

Field	Type	Required	Description
coordinates	array<number>	yes
type	"Point"	no

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

Polygon

Field	Type	Required	Description
coordinates	array<array<array<number>>>	yes	(min items 1)
type	"Polygon"	no

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

Position

A fix. Both coordinates required — that is how the null-never-zero rule is structural.

An unknown position is the ABSENCE of this object (entity.position is None), never a Position holding zeros. Because lat and lon are required here, an adapter cannot express "unknown" as (0, 0) even by accident: it has to either omit the Position or state a real coordinate. Coordinate zero is a real point in the Gulf of Guinea, and a contact painted there is a contact that does not exist.

accuracy_m absent means unknown accuracy, NOT perfect accuracy. Zero would mean a fix with no error, which no sensor produces.

Field	Type	Required	Description
accuracy_m	number | null	no	Metres, 1-sigma. None = unknown, never 0. Default null. (≥ 0)
alt_m	number | null	no	Metres HAE. None = unknown. Default null.
lat	number	yes	WGS84 decimal degrees. (≥ -90; ≤ 90)
lon	number	yes	WGS84 decimal degrees. (≥ -180; ≤ 180)
position_source	PositionSource	yes	How the fix was obtained — the field that survives GNSS denial.
vertical	VerticalPosition | null	no	The height AS THE SOURCE STATED IT — unit and datum carried, never converted. alt_m above stays the canonical HAE-in-metres projection and is None whenever the source's datum is not HAE. Default null.

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

PositionSource

How the position was obtained. Load-bearing in a GNSS-denied environment.

This is the field that lets a commander tell a fix from a guess. When PNTMAP reports jamming over an area, every GNSS-sourced position inside that area becomes suspect and every INERTIAL or MANUAL one does not — a distinction that is impossible to make after the fact if the adapter flattened them all to "position".

Closed vocabulary — a value outside this list is invalid, and UNKNOWN is a

member rather than a null wherever the enum has one.

Value
GNSS
INERTIAL
MANUAL
ESTIMATED

Quality

How good the source says its own data is. Four ways of saying it, none derived.

confidence is 0..1 and comparable across sources; source_quality is the source's OWN grade, a free string, because ASTERIX's track quality, AIS's position accuracy flag and a NATO track's evaluation code are three ordinal scales with no defined mapping between them and inventing one would be a fusion decision made inside a translator.

uncertainty is a NAMED dict — {"along_track_m": 40.0, "cross_track_m": 12.0} — rather than a single number, because an error ellipse is not a radius and flattening it loses the orientation that made it worth sending. Names are the source's; the CDM does not fix a vocabulary here, and the unit belongs in the key exactly as signal_strength_dbm carries its own unit in its name.

Field	Type	Required	Description
accuracy_m	number | null	no	Metres, 1-sigma. None = unknown, never 0. Default null. (≥ 0)
confidence	number | null	no	0..1. None = unknown; 0 means certainty-that-not, which is a claim. Default null. (≥ 0; ≤ 1)
source_quality	string | null	no	The source's own grade, verbatim. None = the source stated none. Default null. (min length 1)
uncertainty	object<string, number>	no	Named components, e.g. along_track_m / cross_track_m. The unit is in the key. Empty = the source named none.

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

Residual

Source information the CDM does not model, kept under the name of the format it came from.

§28's container, and its two rules are load-bearing in opposite directions:

1. It MUST identify its origin. namespace is the source format's own name — the same string as the adapter's metadata.format.name — so a reader meeting an unfamiliar key inside data can find out which standard's vocabulary it belongs to. An unnamespaced bag of leftovers is the free-form dict this model exists to replace.
2. It MUST NOT be treated as semantically trusted merely because it survived translation. A residual says "the source said this and the CDM has no home for it". It is a fact about the source RECORD, not an assertion about the world. A consumer MUST NOT promote a residual value into a canonical field, and a later adapter MUST NOT read another adapter's residual as an input — ARCHITECTURE.md §5 states both as normative text.

data preserves the source's own STRUCTURE, which is why it is a dict and not a list of dotted paths: lossless.residual() learned that the hard way when a two-element list came back as two keys named affected_constellations[0] and [1], satisfying the never-drop rule in the letter while destroying the reader's ability to see a list.

THE FOURTEEN ADAPTERS IN THIS REPOSITORY DO NOT USE THIS YET, deliberately. ARCHITECTURE.md §5 rules that they keep their attributes / payload parking under source_extras through the whole of Part 1 and declare residual: legacy in their manifests, because the information is already preserved and paying for a placement change with every golden file and every downstream consumer buys nothing a reader can use (§29: no breaking change for stylistic cleanliness). Every Part 2 adapter declares residual: structured and uses this.

Field	Type	Required	Description
data	object	no	The unconsumed source structure, preserved as the source shaped it.
namespace	string	yes	The source format's name — normally metadata.format.name. Required. (min length 1)

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

Route

Ordered waypoints, the legs between them, and the route's own metadata.

At least two waypoints, because a route to one place from nowhere is a position. sequence values must be distinct — two waypoints numbered 3 make the order unrecoverable, which is the single thing sequence exists to preserve — and every leg must name sequences that exist, because a leg to a waypoint nobody sent is a route with a hole in it that renders as a line to the origin.

Legs may be EMPTY. A source that sends points and no segments has described a route whose legs are the implied consecutive pairs, and manufacturing those pairs here would publish segments the source never stated — including, for a route the source meant as a set of reporting points, segments that are not flyable.

Field	Type	Required	Description
legs	array<RouteLeg>	no	Segments the SOURCE stated. Empty = the source stated none; consecutive pairs are NOT invented here.
metadata	object	no	Route-level source fields with no canonical home — a procedure name, a flight rules letter, an airway designator.
waypoints	array<Waypoint>	yes	At least two. Ordered by sequence, not by list position. (min items 2)

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

RouteLeg

One segment between two waypoints, addressed BY SEQUENCE and not by index.

distance_m and course_deg are optional because they are the SOURCE's numbers when the source states them, and nothing computes them here. Two waypoints determine a great-circle distance, so a computed value is always available — and a computed value that disagrees with the source's is a second truth in the same record, with nothing to say which one a consumer should plan against. The source's own leg lengths often encode a procedure the geometry does not (a DME arc, a holding pattern), which is exactly the information a computation destroys.

Field	Type	Required	Description
attributes	object	no	Leg-specific source fields with no canonical home.
course_deg	number | null	no	Degrees true, [0, 360), as the source states it. None = not stated. Default null. (≥ 0; < 360)
distance_m	number | null	no	Metres, as the SOURCE states it. None = not stated. Default null. (≥ 0)
from_seq	integer	yes	sequence of the waypoint this leg leaves. (≥ 0)
to_seq	integer	yes	sequence of the waypoint this leg reaches. (≥ 0)

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

SourceHash

A digest of the source record, as the ADAPTER computed it. Carried, never computed here.

Rule 5 asks for "source hash where appropriate", and the appropriateness is the adapter's judgement: a hash of a 3-byte AIS sentence identifies nothing an external id does not, while a hash of a 4 MB NITF segment is how an auditor proves the bytes on the wire were the bytes described. So it is optional, and its absence means the adapter did not compute one.

NO HASHING HAPPENS IN THIS PACKAGE. tests/test_cdm_boundary.py asserts that no module under synapse_cdm/ imports hashlib or any crypto library, and this model does not change that: it is a container for a value produced outside the contract layer, exactly as Integrity is a container for a signature this package does not make. algorithm is therefore required and free-form — a digest with no algorithm cannot be reproduced by anyone, and an enum would make the day SHA-3 arrives a MAJOR bump for a string nobody branches on.

Field	Type	Required	Description
algorithm	string	yes	e.g. sha256. Named by the producer. (min length 1)
value	string	yes	The digest, in the producer's own encoding. (min length 1)

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

SourceId

One external identifier for an object — the provenance mapping.

A list of these, not one, because the same object arrives from several systems: the same vessel is an MMSI to AIS, a track number to STANAG 4676 and a UID to TAK. Fusion joins them later; the adapter's job is to record which name its own system used, and never to overwrite another system's entry.

Field	Type	Required	Description
external_id	string	yes	That system's own identifier. (min length 1)
system	string	yes	The external system, e.g. PNTMAP, TAK. (min length 1)

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

SourceRef

Which adapter produced this object, from which system, and whether it is real.

synthetic is required and has no default. Every fixture in this repository is synthetic and every scenario package is too (TR-12), and the platform keeps the synthetic and live layers apart over one interface — so an object that does not say which layer it belongs to cannot be filed. A default of false would silently promote exercise data to operational data, which is the dangerous direction; a default of true would silently demote live data and hide it from an operator. There is no safe default, so there is no default.

Field	Type	Required	Description
adapter	string	yes	Adapter name, e.g. pntmap. (min length 1)
adapter_version	string	yes	Adapter semver: MAJOR.MINOR.PATCH, no leading zeroes, nothing else. (pattern ^(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)$; min length 1)
format_name	string | null	no	The source STANDARD's name, e.g. 'ASTERIX'. Filled from the adapter's own declared metadata.format; None only for an adapter that declares none. Default null.
format_version	string | null	no	The edition of that standard, e.g. 'Cat 062 ed 1.18'. None = no document in this tree states which edition the adapter targets — a reading, never a gap filled in. Default null.
observed_at	string | null	no	The instant the SOURCE RECORD states for itself, when it states one and no canonical field already carries it. Event.observed_at stays the event's own time; this is the record's. Default null. (pattern ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}Z$)
original_id	string | null	no	The source record's OWN identifier, as a first-class provenance field. Distinct from source_ids, which is the identity of the THING; this is the identity of the RECORD that described it. Default null.
record_index	integer | null	no	Which record of a multi-record payload this object came from, 0-based. None = the payload was not a sequence, or the adapter does not track it. Never -1 and never 0-as-unknown: 0 is the first record. Default null. (≥ 0)
source_hash	SourceHash | null	no	Digest of the source record, computed by the adapter. Default null.
synthetic	boolean	yes	true for anything not from a real source (TR-12).
system	string	yes	The external system this came from. (min length 1)
transformations	array<string>	no	Rule 5's transformation chain: the TRANSFORMS reasons this adapter applied, in the order it applied them. Empty = nothing was transformed, which is a claim the lossless check can contradict.

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

TemporalValidity

The four times an object can have, separated because they answer different questions.

§27's four, and the separation is the point:

observed_at when the SOURCE saw the state valid_from when the state BEGAN, which may be long before anyone saw it valid_to when it ceased. None = still current, never "unknown" effective the period the source declares the object OPERATIVE — an airspace reservation published on Monday, effective Wednesday 0600 to 1200

An airspace restriction shows why one timestamp cannot do the work of four: it is observed when the NOTAM is read, valid from the moment it is published, and effective for a window that has not started yet. Collapsing those into "the time" is how a restriction gets drawn on a map twelve hours early.

EVERY FIELD IS OPTIONAL AND THAT IS DELIBERATE. A source that states only one of the four says one of the four; a model that required more would be filled by adapters copying one instant into three fields, and three copies of one reading look like corroboration. The PRESENCE of this block is itself information — the source described validity in time — and a block with nothing in it is the absence of the block.

§27's epoch rule, stated where it is enforced: unknown time is NOT 1970-01-01 and NOT now(). It is the absence of the field. Timestamp does not refuse the epoch instant, and that is a decision rather than an omission — 1970-01-01T00:00:00Z is a real instant, some sources legitimately carry it as a base epoch, and a validator that refused it would refuse real data in order to catch a defect that lives in the ADAPTER. The rule is therefore enforced where the substitution would be made, in review of the adapter and in the conformance suite's own reading, and it is written down here and in docs/docs/cdm/policies.

Field	Type	Required	Description
effective	Period | null	no	The period the source declares the object operative. Default null.
observed_at	string | null	no	When the source saw it. None = the source did not say. Default null. (pattern ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}Z$)
valid_from	string | null	no	When the state began. None = the source did not say. Default null. (pattern ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}Z$)
valid_to	string | null	no	When it ceased. None = still current / open-ended. Default null. (pattern ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}Z$)

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

VerticalExtent

Lower and upper bounds of a volume. An airspace's floor and ceiling.

Both optional and both may be absent: "surface to unlimited" is a real airspace and it is spelled by two absences, not by 0 and 999999. An extent with neither bound is still worth carrying, because its PRESENCE says the source described a volume rather than a surface.

A bound may be stated in a different unit or against a different datum from the other — a danger area really is published as "surface to FL195" — so no comparison between the two is attempted here. Comparing 0 AGL with FL195 would need a terrain model and a pressure, and a validator that guessed at either would refuse real airspace.

Field	Type	Required	Description
lower	VerticalPosition | null	no	Floor. None = unstated. Default null.
upper	VerticalPosition | null	no	Ceiling. None = unstated. Default null.

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

VerticalPosition

A height, with the unit it was stated in and the datum it was measured from.

§26's rule made structural: value is never alone. Three fields are required together because any two of them without the third is the ambiguity the policy exists to prevent — 600 could be metres or feet, and 600 ft AGL over the Alps is not 600 ft MSL.

NO CONVERSION HAPPENS HERE. This model records; it does not normalise. models.Position keeps alt_m as the canonical HAE-in-metres projection and a validator (there, not here) requires the two to agree when both are stated and the reference really is HAE. When the source's altitude is anything else, alt_m stays None — Rule 2, unknown is not a substituted value — and this block carries what the source actually said. Converting MSL to HAE needs a geoid model, converting a flight level needs the local QNH, and an adapter that performed either silently would be publishing a number nobody measured.

uncertainty is in the SAME unit as value, and is one-sigma, matching Position.accuracy_m's convention. Absent means unknown, never zero: zero would assert a height with no error, which no altimeter and no GNSS receiver produces.

Field	Type	Required	Description
reference	VerticalReference	yes	The datum. UNKNOWN is a member, not null.
uncertainty	number | null	no	1-sigma, in the same unit as value. None = unknown, never 0. Default null. (≥ 0)
unit	VerticalUnit	yes	Never inferred; see VerticalUnit.
value	number	yes	The number the source stated, in unit.

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).

VerticalReference

What a VerticalPosition is measured FROM. The datum, never assumed.

The six here are the ones the formats in scope actually state. HAE is the WGS84 ellipsoid — what a GNSS receiver computes natively and what Position.alt_m has always meant. MSL is a geoid model, and the separation between the two reaches 100 m in places, so a silent substitution moves an aircraft by more than its own vertical separation minimum. AGL is height above the terrain beneath the object, which is not a datum at all but a difference, and is therefore not convertible to either of the others without a terrain model. BARO is an altimeter reading against a stated or unstated pressure setting; FL is BARO against the standard setting.

UNKNOWN is a MEMBER, unlike VerticalUnit's absent one, and the asymmetry is the point: a number with no unit cannot be rendered at all, whereas a number whose datum is unstated can still be shown to an operator beside the words "reference unknown". That is a worse fix than a referenced one and a far better one than a fix silently labelled MSL.

Closed vocabulary — a value outside this list is invalid, and UNKNOWN is a

member rather than a null wherever the enum has one.

Value
HAE
MSL
AGL
BARO
FL
UNKNOWN

VerticalUnit

The unit a VerticalPosition states its number in. §26's "value plus unit", closed.

Three members and no UNKNOWN, which is a departure from this module's opening paragraph and is the unit policy rather than an oversight. §26 forbids "ambiguous naked numeric fields where unit ambiguity matters"; a vertical measurement whose unit nobody knows IS that naked number wearing a wrapper, and recording it would let a consumer render 300 as metres when the source meant feet. An adapter that cannot read the unit therefore has no vertical position to state — it parks the raw number in the residual, where nothing reads it as a height. Absence is expressible (the whole VerticalPosition is optional); an unknown unit is not, deliberately.

FL is a unit as well as a reference because a flight level IS its own scale: FL350 is "35000 feet on the 1013.25 hPa isobaric surface", a number that is neither metres nor feet above anything on the ground. Converting it needs the local pressure, which the adapter does not have, so it is carried as it was stated.

Closed vocabulary — a value outside this list is invalid, and UNKNOWN is a

member rather than a null wherever the enum has one.

Value
m
ft
FL

Waypoint

One ordered point of a route.

sequence is REQUIRED and is the route's order of record. List position would be the obvious alternative and it is the wrong one: a route arrives split across messages, is filtered, is re-sent with one leg amended, and every one of those operations preserves the numbers while destroying the positions. A waypoint that knows its own sequence can be reassembled; one that knows only where it happened to sit in an array cannot.

altitude_constraint is a VerticalPosition rather than a bare number for §26's reason: a crossing restriction published as "FL240" and one published as "8000 ft MSL" are different constraints and the difference is in the unit and the datum, not in the number.

Field	Type	Required	Description
altitude_constraint	VerticalPosition | null	no	A crossing restriction, with its unit and datum. Default null.
eta	string | null	no	Estimated time at this waypoint. None = not estimated. Default null. (pattern ^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\.[0-9]{3}Z$)
name	string | null	no	The source's own designator, e.g. an ICAO fix name. None = unnamed; never an empty string. Default null. (min length 1)
position	Position	yes	Where the waypoint is.
sequence	integer	yes	0-based order of record. Required — see the class docstring. (≥ 0)

additionalProperties: false — unknown keys are rejected. Source-specific fields belong in the declared extension bags (Entity.attributes, Event.payload).