1. A method comprising: disposing a particle motion sensor on a spread of at least one towed streamer; using the particle motion sensor to acquire a measurement of a signal transmitted from an acoustic transmitter, the measurement representing orthogonal particle motions; and based at least in part on the orthogonal particle motions, determining a heading of at least one measurement axis of the particle motion sensor, wherein determining the heading comprises: based at least in part on the measurement, determining a first direction of the signal in a local reference system; and determining the heading based at least in part on the first direction and a second direction of the signal in a global reference system.