The purpose of echo sounding equipment is to provide reliable information on the depth of water under a ship to aid navigation in particular in shallow water.
Echo sounding equipment should comply with the following performance requirements.
These Performance Standards are applicable for ship speeds from 0 up to 30 knots.
Sound speed in water for the purpose of this standard is set at 1500 m/s
Range of depth :- Under normal propagation and sea bed reflectibility conditions the equipment should be capable of measuring any clearance under the transducer between 2 m and 200 m.
Range scales :- The equipment should provide a minimum of two range scales one of which, the shallow range, should cover a range of 20 m, and the other, the deep range, should cover a range of 200 m.
Main display:- The primary presentation should be a suitable graphical display which provides the immediate depth and a visible record of soundings. The displayed record should, show at least 15 min of soundings.
Pulse repetition rate:- The pulse repetition rate should not be slower than 12 pulses per minute on the deep range and 36 pulses per minute on the shallow range.
Roll and pitch:- The performance of the equipment should be such that it will meet the requirements of these performance standards when the ship is rolling ± 10° and/or pitching ± 5°.
If more than one transducer is used:
- Means should be available to display the depths from the different transducers separately; and
- A clear indication of the transducer(s) in use should be provided.
Data storage: It should be possible to record on paper recording or other means the information about:
the depth(s), and the associated time for 12 h.
Accuracy of measurement: Based on a sound speed in water of 1,500 m/s, the tolerance of the indicated depth should be either:
- ± 0.5 m on the 20 m range scale, respectively ± 5 m on the 200 m range scale; or
- ± 2.5% of the indicated depth, whichever is greater.
Discrimination: The scale of display should not be smaller than 5.0 mm per meter depth on the shallow range scale and 0.5 mm per meter depth on the deep range scale.
Malfunctions, alarms and indications: –
- Depth alarm: An alarm signal – both visual and audible with mute function – should be provided when the water depth is below a preset value.
- Failure or reduction in power supply: Alarm signals, both visual and audible (with mute function) to the navigator on the watch should be provided to indicate failure or a reduction in the power supply to the echo sounder which would affect the safe operation of the equipment.
- Operational controls : The function of range scale selection should be directly accessible. The settings for the following functions should be recognizable in all light conditions:
- range scale; and – preset depth alarm.