ASTM D6318-03(2014)
(Practice)Standard Practice for Calibrating a Fathometer Using a Bar Check Method (Withdrawn 2023)
Standard Practice for Calibrating a Fathometer Using a Bar Check Method (Withdrawn 2023)
SIGNIFICANCE AND USE
4.1 The accuracy of depth measurements made by a fathometer or echo sounder requires a number of corrections because of the variability of sound or acoustic velocity in water with changes in temperature, salinity, and depth of water. In addition instability of the equipment can also result in significant errors. For additional information see Practice D5073.
4.2 Calibration of echo sounding instruments is absolutely critical in assuring the adequacy of depth measurements. When an echo sounder has been accurately calibrated, any observed (recorded) depth can be related to the true depth of water. Since the intended purpose of echo sounding is to measure the “true” depth, an independent “true” reference must be used.
4.3 A bar-check is the most wide-spread, easiest to construct, and most economical mechanical method to determine corrections for instrument and velocity errors.
4.4 This procedure explains the calibration of a fathometer or electronic depth sounder using a bar-check.
4.5 Bar-checking techniques and equipment are general in nature and may need to be modified for use in specific field conditions.
SCOPE
1.1 This practice provides the user with procedures used in manually calibrating the fathometer or electronic depth sounder. This narrative describes calibration terminology, describes acceptable environmental conditions for calibration, and describes the calibration procedures.
1.2 The references cited contain useful information in the construction and the correct operation of the calibration equipment.
1.3 Any references cited in this narrative to specific products or brand names are made for information only, and is intended to be descriptive, but not restrictive, of products that will perform satisfactorily.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D6318 − 03 (Reapproved 2014)
Standard Practice for
Calibrating a Fathometer Using a Bar Check Method
This standard is issued under the fixed designation D6318; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.1 bar—a section of metallic channel, I-beam, T-beam,
pipe, plate, or ball that will reflect sound waves produced by a
1.1 This practice provides the user with procedures used in
fathometer.
manually calibrating the fathometer or electronic depth
sounder. This narrative describes calibration terminology, de- 3.2.2 bar-check—a method for calibrating a fathometer by
scribes acceptable environmental conditions for calibration, setting a sound or accoustic reflector (bar) below a survey
and describes the calibration procedures. vessel to a known depth below a sounding transducer.
1.2 The references cited contain useful information in the 3.2.3 draft (transducer draft)—the vertical distance from
construction and the correct operation of the calibration equip- the bottom of the transducer to the surface of the water.
ment.
3.2.4 fathometer—An electronic device for registering
1.3 Any references cited in this narrative to specific prod- depths of water by measuring the time required for the
ucts or brand names are made for information only, and is transmission and reflection of sound waves between a sonic
intended to be descriptive, but not restrictive, of products that transducer and the lake or river bottom.
will perform satisfactorily.
3.2.5 sound—to determine the depth of water.
1.4 The values stated in inch-pound units are to be regarded
3.2.6 sounding scroll—the chart record of an underwater
as standard. The values given in parentheses are mathematical
cross section or profile of the bottom.
conversions to SI units that are provided for information only
3.2.7 transducer—a device for translating electrical energy
and are not considered standard.
to acoustical energy and acoustical energy back to electrical
1.5 This standard does not purport to address all of the
energy.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Significance and Use
priate safety and health practices and determine the applica-
4.1 The accuracy of depth measurements made by a fath-
bility of regulatory limitations prior to use.
ometer or echo sounder requires a number of corrections
2. Referenced Documents because of the variability of sound or acoustic velocity in water
with changes in temperature, salinity, and depth of water. In
2.1 ASTM Standards:
addition instability of the equipment can also result in signifi-
D1129 Terminology Relating to Water
cant errors. For additional information see Practice D5073.
D5073 Practice for Depth Measurement of Surface Water
4.2 Calibration of echo sounding instruments is absolutely
3. Terminology
critical in assuring the adequacy of depth measurements. When
an echo sounder has been accurately calibrated, any observed
3.1 Definitions—Refer to Terminology D1129 for terms
(recorded) depth can be related to the true depth of water. Since
used in this guide.
the intended purpose of echo sounding is to measure the “true”
3.2 Definitions of Terms Specific to This Standard:
depth, an independent “true” reference must be used.
4.3 A bar-check is the most wide-spread, easiest to
This practice is under the jurisdiction of ASTM Committee D19 on Water and
construct, and most economical mechanical method to deter-
is the direct responsibility of Subcommittee D19.07 on Sediments, Geomorphology,
mine corrections for instrument and velocity errors.
and Open-Channel Flow.
Current edition approved Jan. 1, 2014. Published March 2014. Originally
4.4 This procedure explains the calibration of a fathometer
approved in 1998. Last previous edition approved in 2008 as D6318 – 03 (2008).
or electronic depth sounder using a bar-check.
DOI: 10.1520/D6318-03R14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.5 Bar-checking techniques and equipment are general in
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
nature and may need to be modified for use in specific field
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. conditions.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6318 − 03 (2014)
5. Apparatus depths less than 100 ft. Reasonable results, however, can be
obtained during wind velocities between 5 and 15 mph. But
5.1 The device used for bar-checking must be a sound-
when wind velocities are greater than 15 mph and depths
reflecting surface that can be lowered to a known depth below
greater than 100 ft, some error will exist in the soundings.
the transducer of the survey vessel. See Fig. 1. These sounding-
refecting surfaces (or sounding targets) can be a bar made out
6.2 Bar checks should always be made when and where
of a section of metallic I-beam or T-beam, pipe, a rectangular water conditions are calmest; observations taken during rough
section of sheet metal, or a section of metal screen.
water conditions or when differential current causes the bar to
be displaced from a position vertically below the transducer are
5.2 Bars used in depths greater than 30 ft (10 m) should be
subject to unacceptable magnitudes of error.
at least 9 in. (23 cm) wide. The dimensions of the target depend
on the type of survey vessel, location of the transducer, and the
6.3 For best results where salinity and temperature of the
depth range to be covered during the survey. Usually, the
water are unknown, the fathometer should be calibrated before
length of the bar is equal to the beam or width for small survey
the start, at midday and at the end of each day’s work to check
vessels. For larger vessels, a spherical metal ball or steel plate
the accuracy of the soundings. However, if stable water
is lowered through a well in the hull.
conditions are known to exist, it is possible to limit the number
of bar-checks to one per day before the start of the work.
5.3 The weight of the bar will be dependent on the type of
currents experienced, typical project depths, and beam of the
6.4 A survey vessel operating in exposed rough water or
vessel. Typical weights range from 40 to 100 lb (20 to 50 kg).
windy conditions should run to a protected area for the bar
In deep water areas with large currents, a heavy bar is essential
check. Bar checks, however, should not be made in areas where
because subsurface currents will pull to light a bar from the
salinity, temperatures, and suspended sediment concentrations
transducer’s vertical plane. On small, shallow inland or pro-
vary significantly from
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