ROCA is a timed race in which individual competitors use a topographic map and a magnetic compass to navigate through diverse, wooded terrain while searching for radio transmitters.
Transmitters may identify themselves in Morse code or with voice recordings, and only transmit for ten seconds during every minute of the competition.
The transmitters are physically small, and marked with a control card that is no larger than a typical postcard with a unique number identification.
Because of the low power and short distances involved, most ROCA competitors walk the entire course, and focus their attention on the radio direction finding tasks rather than navigation.
ROCA events can be found today primarily in the San Francisco Bay area of the United States and in the People's Republic of China.