# What is the unit for ground speed reported by ADS-B?

Strangely enough, I'm having trouble finding the unit reported by ADS-B on the Internet. Many sites simply refer to it as "ground speed". Is it measured in KPH?

• FWIW, I googled "ADS-B goundspeed readout". The second entry that came up was for faa.gov/documentLibrary/media/Advisory_Circular/AC20-172B.pdf. In that document, the only unit I saw for distance was nautical miles, and the only unit I saw for speed was knots. Apr 1 '18 at 21:15

ADS-B* encodes the ground speed in NM/s (nautical miles per second) in $2^{15}$ increments of ≅ 0.22 knots each such that: