There must, Franklin decided, be powerful currents scouring this area clear - but there was certainly no current now, as his drift meter assured him.

An ion drift meter is a device used to measure the velocity of individual ions in the area of a spacecraft.

An Ion drift meter, which measured the ambient ion drift.

It is believed his head was impaled on a drift meter during the ditching of the Cathay Pacific airliner.

A drift meter, also drift indicator and drift sight, is an optical device used to improve dead reckoning for aircraft navigation.

Ion drift meters have been used on several spacecraft including Dynamics Explorer and CHAMP, and will be on board the forthcoming Ionospheric Connection Explorer mission.

SSIESS includes a Retarding Potential Analyzer (RPA), and Ion Drift meter (IDM), a scintillation meter, and a Langmuir probe.

For most of the history of air navigation, this was accomplished through a reverse dead reckoning process, timing the passage of objects on the ground to measure ground speed, and either estimating the drift or measuring it with simple optical instruments like the drift meter.