 thumb|cutaway of an anschÃ¼tz gyrocompass thumb|a gyrocompass repeater a gyrocompass is a type of non-magnetic compass which is based on a fast-spinning disc and rotation of the earth (or another planetary body if used elsewhere in the universe) to automatically find geographical direction. although one important component of a gyrocompass is a gyroscope, these are not the same devices; a gyrocompass is built to use the effect of gyroscopic precession, which is a distinctive aspect of the general gyroscopic effect. gyrocompasses are widely used for navigation on ships, because they have two significant advantages over magnetic compasses: * they find true north as determined by earth's rotation, which is different from, and navigationally more useful than, magnetic north, and * they are unaffected by ferromagnetic materials, such as ship's steel hull, which change the magnetic field == operation == a gyroscope, not to be confused with gyrocompass, is a spinning wheel mounted on gimbal so that the wheel's axis is free to orient itself in any way. when it is spun up to speed with its axis pointing in some direction, due to the law of conservation of angular momentum, such a wheel will normally maintain its original orientation to a fixed point in outer space (not to a fixed point on earth). since our planet rotates, it appears to a stationary observer on earth that a gyroscope's axis is completing a full rotation once every 24 hours.although the effect is not visible in a specific case when the gyroscope's axis is precisely parallel to the earth's rotational axis. such a rotating gyroscope is used for navigation in some cases, for example on aircraft, where it is known as heading indicator, but cannot ordinarily be used for long-term marine navigation. the crucial additional ingredient needed to turn such gyroscope into a gyrocompass, so it would automatically position to true north, is some mechanism that results in an application of torque whenever the compass's axis is not pointing north. one method uses friction to apply the needed torque:gyrocompass, auxiliary gyrocompass, and dead reckoning analyzing indicator and tracer systems, san francisco maritime national park association. the gyroscope in a gyrocompass is not completely
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