Tuesday 12 March 2013

IMO PERFORMANCE STANDARDS FOR SPEED AND DISTANCEMEASURING EQUIPMENT (SDME)


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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