IMO PERFORMANCE STANDARDS
FOR SPEED AND DISTANCEMEASURING EQUIPMENT (SDME)
IMO PERFORMANCE STANDARDS FOR DEVICES TO
INDICATE SPEED
AND DISTANCE (SDME)Devices to indicate speed and distance are
intended for generalnavigational and ship maneuvering use. Although the
minimumrequirement is to provide information on the distance run and
theforward speed of the ship through the water or over the
ground,additional information on ship's motions other than in the
forwardaxis may be provided. The equipment should comply fully with
itsperformance standard at forward speeds up to the maximum speedof the
ship and in water of depth greater than 3 m beneath the keel.Devices to
indicate speed and distance should comply with thefollowing minimum performance requirements.1.
Speed information may be presented in either analogue or digitalform.
Where a digital display is used, its incremental steps shouldnot exceed
0.1 knots. Analogue displays should be graduated atleast every 0.5 knots and
be marked with figures at least every 5knots. If the display can present
the speed of the ship in other thanthe forward direction, the direction
of movement should beindicated unambiguously.2. Distance run
information should be presented in digital form. Thedisplay should cover
the range from 0 to not less than 9999.9nautical miles and the incremental
steps should not exceed 0.1nautical miles. Where practicable, means should
be provided forresetting readout to zero. The display should be easily readable
byday and by night.3. Means should be provided for feeding distance run
information toother equipment fitted on board.4. If equipment is capable of
being operated in either the "speedthrough the water" or
"speed over the ground" mode, modeselection and mode indication
should be provided.5. If the equipment has provision for indicating
speeds other than ona single fore and aft axis, then the forward and
athwart speedthrough the water must be provided, and the forward and
athwartspeed over the ground may be provided as an additional
option.Resultant speed and course information may be provided as aswitchable
option. All such information should clearly indicate thedirection, mode and
validity status of the displayed information.6. Errors in the indicated
speed, when the ship is operating freefrom shallow water effect and from the
effects of wind, current andtide, should not exceed 2% of the speed of the
ship, or 0.2 knots,whichever is greater.7. Errors in the indicated
distance run, when the ship is operatingfree from shallow water effect and from
the effects of wind, currentand tide, should not exceed 2% of the
distance run by the ship in 1h or 0.2 nautical miles in each hour, whichever is
greater.8. If the accuracy of devices to indicate speed and distance run
canbe affected by certain conditions (e.g. sea state and its effects,water
temperature, salinity, sound velocity in water, depth of waterunder the
keel, heel and trim of ship), details of possible effects
should be included
in the equipment handbook.9. The performance of the equipment should be
such that it willmeet the requirements of these standards when the
ship is rollingup to + 10
°
and pitching up to + 5
°
.10. The system should
be so designed that neither the method of attachment of parts of the
equipment to the ship nor damageoccurring to any part of the equipment which
penetrates the hullcould result in the ingress of water to the ship.11. Where
any part of the system is designed to extend from andretract into the hull
of the ship, the design should ensure that it canbe extended, operated
normally and retracted at all speeds up tothe maximum speed of the ship. Its
extended and retractedpositions should be clearly indicated at the display
position.
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