ISO 9875:1996
(Main)Ships and marine technology — Marine echo-sounding equipment
Ships and marine technology — Marine echo-sounding equipment
Navires et technologie maritime — Appareils de sondage par écho
General Information
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Standards Content (Sample)
INTERNATIONAL
IS0
STANDARD
9875
Second edition
1996-08-o 1
Ships and marine technology - Marine
echo-sounding equipment
Navires et technologie maritime - Appareils de sondage par &ho
Reference number
IS0 9875: 1996(E)
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IS0 9875:1996(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide fed-
eration of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard IS0 9875 was prepared by Technical Committee
lSO/TC 8, Ships and marine technology, Subcommittee SC 6, Navigation.
This second edition cancels and replaces the first edition (IS0 9875:1991),
which has been technically revised.
Annex A forms an i ntegral part of this International Standard. Annex B is
for info rmation only
0 IS0 1996
All rights reserved. Unless otherwise specified, no part of this publication may be
reproduced or utilized in any form or by any means, electronic or mechanical, including
photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
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IS0 9875:1996(E)
INTERNATIONAL STANDARD o Iso
Ships and marine technology - Marine echo-sounding
equipment (
International Convention for the Safety of Life at Sea
1 Scope
(SOLAS 1981), Chapter V, Regulation 12: Shipborne
navigational equipment.
This International Standard specifies the performance
and type testing of marine echo-sounding equipment
IMO Resolution A.224(VI I), Performance standards for
required by Regulation 12 of Chapter V of the Inter-
echo-sounding equipment.
national Convention for the Safety of Life at Sea, 1967
(SOLAS 1981) as amended.
IMO Resolution A.694( 17), Genera/ requirements for
shipborne radio equipment forming part of the global
It establishes, when used in conjunction with IEC 945,
maritime distress and safety system (GMDSS) and for
minimum performance standard test methods and
electronic navigational aids.
required test results for marine echo-sounding equip-
ment which measures the depth of water under a ship
by transmitting pulsed acoustic energy and timing the
return of the echo from the sea-bed.
3 Definitions
Clause 4 gives the performance requirements, based
For the purposes of this International Standard, the
on IMO Resolution A.224(VI I).
following definitions apply.
of the test methods and the re-
Clause 5 consists
quired test results.
3.1 source level, S: Maximum rms (root-mean-
square) sound pressure level, expressed in decibels
All requirements (I with the exception of numerical
relative to 1 PPa, at a point on the principal axis of the
values and their units) that are extracted from the
transducer, as measured in the far field but referred to
recommendations of IMO Resolution A.224(Vll) are
the distance of 1 m.
printed in italics.
3.2 directivity index, D: Ratio, expressed in deci-
bels, of the acoustic power density at a distant point
on the principal axis of the transducer, when used as a
2 Normative references
transmitter, to that of an omnidirectional transducer,
with the same total radiated acoustic power.
The following standards contain provisions which,
through reference in this text, constitute provisions of
3.3 receiving bandwidth, B: 10 loglo (fl -f2), ex-
this International Standard. At the time of publication,
pressed in decibels relative to 1 Hz, where fl and f2
the editions indicated were valid. All standards are
are the upper and lower frequencies respectively in
subject to revision, and parties to agreements based
hertz at which the response of the overall system,
on this International Standard are encouraged to in-
measured through water, is 3 dB below the maximum
vestigate the possibility of applying the most recent
response of the system.
editions of the standards indicated below. Members
of IEC and IS0 maintain registers of currently valid
3.4 minimum detectable signal-to-noise ratio, E:
International Standards.
Ratio, expressed in decibels, of the signal level to the
background noise level in the bandwidth of the re-
IEC 945:1994, Marine navigational equipment - Gen-
ceiver required to give a minimum detectable signal
eral requirements - Methods of testing and required
on the display.
test results.
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@ IS0
IS0 9875: 1996(E)
4.4.2 The record shall, on the deep range scale,
4 Requirements
show at least 15 min of soundings.
4.1 General requirements
4.4.3 Where paper is used for recording depth on the
4.1.1 General requirements of the echo-sounding
graphical display, either by marks on the recording
equipment shall be in accordance with IEC 945:1994,
paper, or by other means, there shall be a clear
clause 3.
indication when the paper remaining is less than ap-
proximately 10 % of the original roll length.
4.1.2 The echo-sounding equipment shall provide
reliable information on the depth of water under a ship
4.4.4 The equipment shall have the function of dis-
to aid navigation.
playing time in time mark at an interval of 3 min or
less. The accuracy shall be + 5 %.
4.1.3 If an acoustic depth alarm is fitted, the acoustic
signal emitter shall be tested. During this test, the
functions of the echo-sounding equipment shall not be
affected. When numerical displays conforming to 4.5 Safety
IEC 945:1994, subclause 3.2.7.1, are used, this test
may be combined with segment testing.
In the case of equipment using a high voltage electro-
sensitive recording medium and/or a moving writing
mechanism, and where access to the record is poss-
ible while the echo-sounding equipment is operating,
4.2 Range of depths
the equipment shall provide for operator safety.
Under normal propagation conditions, the equipment
shall be capable of measuring any clearance under the
4.6 Pulse repetition rate
transducer between 2 m and 400 m.
The pulse repetition rate shall not be slower than
12 pulses per minute.
4.3 Range scales
4.3.1 The equipment shall provide a minimum of two
4.7 Measurement accuracy
range scales, one of which, the deep range, shall
cover the whole depth range, and the other, the shal-
4.7.1 Based on a sound speed in water of 1 500 m/s,
low range, the first one-tenth of the range.
the allowable tolerance on the indicated depth shall be
either
4.3.1.1 Range scales in addition to those required in
4.3.1 may be provided.
+ 1 m on the shallow range scale, and
4.3.1.2 Positive indication of the range in use shall be
+ 5 m on the deep range scale;
provided in all cases.
or
4.3.1.3 Where phased ranges, not starting from zero,
are available, an indication shall be provided to show - + 5 % of the indicated depth,
when such a range is in use.
whichever is the greater.
4.3.2 The scale of display shall not be smaller than
NOTE 1 These tolerances take no account to ship roll and
2,5 mm per metre depth on the shallow range scale
pitch.
and 0,25 mm per metre depth on the deep range
scale.
4.7.2 Where a set zero control is provided, this shall
be for use in calibration and installation and shall not
4.4 Method of presentation be made available as an operator control.
4.4.1 The primary presentation shall be a graphical
display which provides the immediate depth and a 4.7.3 Where depth measurement relative to the sea
surface is provided, in addition to measurement of the
visible record of soundings. Other forms of display
may be added but these shall not affect the normal depth of water under the ship, there shall be positive
operation of the main display. indication of the mode of operation in use.
2
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0 IS0 IS0 9875:1996(E)
4.8 Roll and pitch it. Initially, the transducer shall be directed towards
the calibrated hydrophone.
The performance of the equipment shall be such that
NOTE 2 See [I], [Z] and [3] for details.
it will meet the requirements of this International
Standard when the ship is rolling + IO0 and/or pitching
In order to minimize near-field effects, distance d, in
+ 5O.
metres, shall not be less than
1 ,25a2flc
4.9 Power supply
where
The power supply of the equipment shall be in accor-
a is the largest active dimension of the trans-
dance with IEC 945:1994, subclause 3.3.
ducer element, in metres, appropriate to the
mode of use i.e. transmission or reception
(usually the same figure for either);
4.10 Environmental conditions
is the highest operation frequency of the
f
echo-sounding equipment in hertz;
Weatherproofing and exposure-to-weather integrity
of the equipment shall be in accordance with
c is the sound speed in water, equal to
I EC 945: 1994, subclause 3.4.
I 500 m/s (see 4.7.1).
Precautions shall be taken to minimize the effects of
4.11 Interference reverberation in the water. These precautions shall
include the use of gated pulse measurement tech-
niques. These techniques will be essential in the case
The equipment shall comply with the requirements for
of some echo-sounding equipment receivers that op-
interference given in IEC 945:1994, subclause 3.5.
erate in a non-linear mode.
5.3 Range of depths
5 Test methods and required test results
53.1 Minimum depth indication
5.1 General
5.3.1 .I Test method
Any requirement in clause 4 for which no test is
specified in this clause or in IEC 945:1994, clause 4,
The transducer in its housing, complete with acoustic
shall be checked by inspection of the equipment, the
window if provided, shall be normally connected and
manufacturer’s drawings or the relevant documents.
immersed in water with its axis of maximum response
The result of the inspection shall be stated in the test
directed towards (i.e. normal to) an echoing boundary
report.
surface such as the bottom or side of the tank holding
the water. It shall be possible to adjust and to measure
the physical distance between the transducer and the
boundary surface from 0 to not less than 2 m.
5.2 General underwater test conditions
The test shall be conducted such that no other object
The equipment transducer in its housing, complete
or discontinuity shall be capable of affecting the result
with acoustic window if provided, shall be attached
significantly.
underwater to a clamp calibrated in degrees to enable
the transducer to be rotated to any required angle
The equipment shall be set to the shallow scale with
about the major axis of the face of its element (i.e.
the longest pulse length available on that scale and
about the longer axis, which will run parallel to the
the physical distance between the transducer and
ship fore-and-aft line) and about the minor axis (the
the boundary surface shall be adjusted until the echo
athwartships axis) where the element is rectangular or
from this surface is just indicated separately and dis-
elliptical, or about any facial axis where the element is
tinctly on the display. This physical distance shall be
circular.
measured and noted as the minimum depth indication.
A calibrated hydrophone, which can be replaced by a
calibrated projector (or, alternatively, a single instru-
5.3.1.2 Result required
ment capable of being used in either role as required)
shall be mounted under the water as a suitable known
The minimum depth indication shall not be greater
distance, d, from the transducer and directed towards
than 2 m.
3
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IS0 9875:1996(E)
5.32 Maximum required measurable depth 5.3.2.2 Test methods
5.3.2.2.1 Source level, S
5.3.2.1 Figure of merit
.
The transducer shall be immersed in water with its
The equipment shall be tested by the assessment,
principal axis directed towards a calibrated hydro-
under laboratory conditions, of the system figure of
phone and lead (also immersed in the water) and situ-
merit for a water depth of 400 m.
ated at a known distance, d, in metres, in the far
sound field from the transducer. The equipment shall
The figure of merit, L’, expressed in decibels, is
be switched on.
defined as
The source level, S, is given by
. . .
L’=S--2r+D-B-E (1)
s=(v+120)-M+2010glod
and shall exceed Lo as indicated by the following rela-
tionship:
M is the known response of the hydrophone
. . .
L0=L+2aR+K+Ns+x+y+z (2)
and lead, in decibels relative to 1 jWpPx
V is the rms output voltage of the hydro-
phone and lead, in decibels relative to 1 V,
is the source level, in decibels relative to
s
measured during the pulse and averaged
1 PPa at 1 m;
over its duration.
I- is the one-way loss figure due to roll and
pitch, in decibels;
5.3.2.2.2 Roll and pitch, r
is the receiving directivity index, in decibels;
D
This test may be waived where suitable transducer
beam direction stabilization is provided and can be
B is the receiving bandwidth, in decibels rela-
demonstrated. Otherwise the one-way loss figure de-
tive to 1 Hz;
scribed below shall be determined to allow for the roll
E is the minimum detectable signal-to-noise
and pitch criteria specified in 4.8. The one-way loss
ratio, in decibels;
figure, r, shall be the greatest reduction in response
obtained when the source level measurement in
L is the spreading loss due to divergence,
5.3.2.2.1 is repeated with the transducer element
equal to 20 loglo (2 OOOR);
rotated by up to + 10” about its roll axis and at the
same time by up to + 5O about its pitch axis.
R is the depth, in kilometres;
a is the sound absorption coefficient of sea
5.3.2.2.3 Directivity index, D
water in decibels per kilometre (see annex A):
combining R and a gives
This test may be carried out, at the discretion of the
type test authority, with the transducer used in the
2aR, as the total water attenuation loss,
transmitting mode as in 5.3.1 and 5.3.2.2.1, but
in decibels;
whenever practicable, the receiving mode described
K is the bottom reflection loss at normal inci-
as follows shall be used.
dence and is taken to be 25 dB;
The transmitter shall be disabled, but the trigger shall
Ns is the noise background level, in decibels
be available for external use. With the transducer and
relative to 1 PPa in a 1 Hz bandwidth, equal
a test projector directed towards each other, and the
to 82,5 - (50/3) loglof;
projector energized from a suitable pulsed signal
source, the output voltage of the receiver of the echo-
x is the transmission loss in the case when the
sounding equipment shall be monitored.
transducer is mounted inside the hull, in
decibels;
The pulse from the pulsed signal source shall be trig-
gered by the echo-sounding equipment and delayed
is a signal excess of 10 dB above the mini-
Y
suitably to correspond with a definite depth within the
mum detectable signal-to-noise ratio to pro-
scale. This pulse shall simulate the pulse normally
vide a practical working level under all
transmitted by the equipment in regard to duration.
conditions;
The carrier frequency shall be adjusted to give maxi-
is a manufacturing tolerance of 3 dB.
z mum response on the echo-sounding equipment.
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IS0 9875:1996(E)
@ IS0
A continuous random noise voltage of bandwidth
Using the method of maintaining constant receiver
output voltage by varying the signal source voltage equal to the bandwidth of the equipment receiving
system and at a level well below saturation shall be
suitably, a pattern shall be plotted of transducer re-
sponse against positive and negative angles of ro- added to a simulated echo pulse of variable amplitude
which shall be triggered from the equipment delayed
tation of the transducer about each of its appropriate
suitably to correspond with a definite depth within the
axes, in order to find the angular beam width, 8, in
shallow range scale. The combined signal shall be
degrees, between the two points giving a level 3 dB
applied from a low-impedance source in series with
below maximum response.
the transducer. The level of the echo shall be adjusted
The directivity index D shall be calculated as fol
...
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