Also known as: compact position reporting, CPR

Compact position reporting (CPR) is the encoding ADS-B uses to convey an aircraft’s latitude and longitude in few bits, trading a small amount of ambiguity for compactness.¹

Compact position reporting (ADS-B) combines an even and odd message to pin down a position with few bits.

How it works

CPR encodes position relative to a grid of zones. A globally unambiguous fix is recovered from a matched pair of even and odd format messages, or locally from a known reference position.

Relevance to SDR

An ADS-B decoder must implement CPR to turn raw messages into mappable aircraft positions.

Sources

1. Automatic Dependent Surveillance–Broadcast — Wikipedia, for ADS-B and its compact position-reporting encoding. ↩

See also

• ADS-B
• Cyclic redundancy check (CRC)
• ICAO

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