Which ETSI standard defines the CPM?

ETSI TS 103 324 defines the Collective Perception Service and the CPM. It draws its data types from the Common Data Dictionary, ETSI TS 102 894-2, and its pre-standardization analysis is TR 103 562.

What is the CPM messageID?

The CPM carries messageID 14 in the ITS PDU header, which the decoder reads to auto-detect the type. Its protocolVersion is 2 in Release 2.

v2json / messages / CPM

V2X message reference

The Collective Perception Message

Q: What is inside a CPM?

A management container with the sender's reference position and time, optional containers describing the originating station and its sensors, and a perceived-object container listing each detected object with its position relative to the sender, its measurement age and per-object confidence.

Q: How do I decode a CPM message?

POST the hex UPER stream to https://v2json.skyv2x.com/api/v1/decode with {"hex":"..."}. The response is structured JSON with the containers, enums resolved and coordinates in decimal degrees. No SDK or local ASN.1 toolchain is needed.

A CPM is how a vehicle or roadside unit tells its neighbours what its sensors see. Below: what it carries, the ETSI clauses that define each part, and a real one decoded to JSON.

What is a Collective Perception Message?

A CPM is the ETSI V2X message a station broadcasts to share its perception of the world around it: the other road users and objects its sensors detect, each with a position, kinematics and a confidence. It lets a station warn its neighbours about traffic they cannot see for themselves. It is defined in ETSI TS 103 324 and carries messageID 14.

What is inside a CPM?

The message is a header plus a set of containers. The ones that matter most:

Container	Holds	Clause (TS 103 324)
Management	The sender's `referencePosition` and reference time. Every perceived object is expressed relative to this anchor.	7.1.3
Originating station	The sender's own orientation and, for a vehicle, its dimensions, so a receiver can place the anchor.	7.1.4
Perceived object	Each detected object: an `objectId`, a Cartesian offset from the reference position, kinematics, and a per-object confidence.	7.1.8

One field to read with care is measurementDeltaTime (7.1.8.2): it is per object, so two objects in the same message can be dated at different instants. The reconstruction of a 95% confidence from the reported components is set out in Annex C.

A real CPM, decoded

A vendor reference CPM (66 bytes) through the API, with enrich: true. Enriched siblings appear next to coded fields: coordinates in decimal degrees, enums resolved.

POST /api/v1/decode → JSON (excerpt)

{
  "header": { "protocolVersion": 2, "messageId": 14, "stationId": 99999,
             "_messageId_name": "CPM" },
  "payload": {
    "managementContainer": {
      "referenceTime": 689686032850,
      "referencePosition": {
        "latitude": 488700000,  "longitude": 23500000,
        "_latitude_decoded": "48.8700000",  "_longitude_decoded": "2.3500000"  // degrees
      }
    },
    "cpmContainers": [
      { "containerId": 5, "containerData": {
          "numberOfPerceivedObjects": 1,
          "perceivedObjects": [
            { "objectId": 1, "measurementDeltaTime": 0,
              "position": { "xCoordinate": { "value": 1000, "confidence": 100 } } }
          ] } }
    ]
  }
}
… full container tree in the workbench.

Open this message in the workbench →

How do I decode a CPM message?

Send the hex to /api/v1/decode. No SDK, no local ASN.1 toolchain.

curl

curl -s -X POST https://v2json.skyv2x.com/api/v1/decode \
  -H 'Content-Type: application/json' \
  -d '{"hex":"<your CPM hex>","type":"cpm","enrich":true}'

The integration guide has the same in Python, JavaScript and Node.js, plus encode and round-trip.

Which standard defines the CPM?

Standard

ETSI TS 103 324 V2.1.1

messageID

Data types

Common Data Dictionary, TS 102 894-2 V2.1.1

Analysis

TR 103 562

The CPM is a perception message an intersection or roadside unit broadcasts as readily as a vehicle does. For where it sits in an infrastructure deployment, see V2X for infrastructure.

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