This document outlines the International Maritime Organization's (IMO) performance standards for rate of turn indicators (ROTI) installed on ships. The ROTI must be capable of indicating port and starboard turns, have a means to verify operation, and use a center-zero analog dial indicator with positive indications for port and starboard turns. The scale must allow measurement of turns between -30 and 30 degrees per minute and meet accuracy standards for deviations from the actual turn rate under various ship motions and speeds.

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IMO PERFORMANCE STANDARDS FOR RATE OF TURN
INDICATORS (R.O.T.I.)
(FOR MMD PHASE II EXAMINATIONS)
Rate of Turn Indicators fitted onboard ships shall comply with
following IMO performance standards:
1. The Rate-of-Turn Indicator (ROTI) shall be capable of indicating rates of
turn to starboard and to port of the ship to which it is fitted.
2. The ROTI may be self-contained; or it may form part of, or derive
information from, any other appropriate equipment.
3. The ROTI shall include a means of enabling the operator to verify that it is
operating.
4. The indication required shall be provided by a centre-zero analogue type
indicator (preferably circular). Where a circular scale indicator is used, the
zero shall be uppermost.
5. A turn of ship to port shall be indicated on the left of the zero point and a
starboard turn to the right of the zero point. If the actual rate of turn
exceeds full scale deflection, this shall be clearly indicated on the display.
6. In addition, an alphanumeric display may be provided. Positive indication
of port and starboard shall be provided on such displays.
7. The length of scale in either direction from zero shall not be less than
120 mm. The sensitivity of the system shall ensure that a change in the rate
of turn of one degree per minute is represented by a distance of not less
than 4 mm on its scale.
8. A linear range scale of not less than ± 30 degrees per minute shall be
provided. This scale shall be marked in intervals of one degree per minute
on both sides of zero. The scale shall be marked with figures every 10
degrees per minute. Every 10 degree mark shall be significantly longer
than the 5 degree mark which in turn shall be significantly longer than the
one degree mark. The marks and figures shall preferably be red or a light
color on a dark background. Additional linear range scales may be
provided.
9. Periodic rolling motion of the ship with an amplitude of ± 5 degrees and
period of up to 25 seconds and periodic pitching motion with an amplitude
of ± 1 degree and period of up to 20 seconds shall not change the mean
value of the indicated rate of turn by more than 0.5 degrees per minute.

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10.The indicated rate of turn shall not deviate from the actual rate of turn of
the ship by more than 0.5 degrees per minute plus 5 per cent of the
indicated rate of turn of the ship. These values include the influence of
earth rate.
11.The ROTI shall meet these accuracy requirements at all ship speeds up to
10 knots.
12.The ROTI shall be ready for operation and comply with these standards
within 4 minutes of being switched on.
13.The design shall be such that whether operating or not, the ROTI will not
degrade the performance of any other equipment to which it is connected.
14.Damping of the ROTI shall be provided with a time constant which may be
varied during operation in the range zero to at least 10 seconds.