ASTM D6318-03
(Practice)Standard Practice for Calibrating a Fathometer Using a Bar Check Method
Standard Practice for Calibrating a Fathometer Using a Bar Check Method
SIGNIFICANCE AND USE
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 D 5073.
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.
A bar-check is the most wide-spread, easiest to construct, and most economical mechanical method to determine corrections for instrument and velocity errors.
This procedure explains the calibration of a fathometer or electronic depth sounder using a bar-check.
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 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.
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Designation:D6318–03
Standard Practice for
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Calibrating a Fathometer Using a Bar Check Method
This standard is issued under the fixed designation D 6318; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope* transmission and reflection of sound waves between a sonic
transducer and the lake or river bottom.
1.1 This practice provides the user with procedures used in
3.2.5 sound—to determine the depth of water.
manually calibrating the fathometer or electronic depth
3.2.6 sounding scroll—the chart record of an underwater
sounder. This narrative describes calibration terminology, de-
cross section or profile of the bottom.
scribes acceptable environmental conditions for calibration,
3.2.7 transducer—a device for translating electrical energy
and describes the calibration procedures.
to acoustical energy and acoustical energy back to electrical
1.2 The references cited contain useful information in the
energy.
construction and the correct operation of the calibration equip-
ment.
4. Significance and Use
1.3 Any references cited in this narrative to specific prod-
4.1 The accuracy of depth measurements made by a fath-
ucts or brand names are made for information only, and is
ometer or echo sounder requires a number of corrections
intended to be descriptive, but not restrictive, of products that
becauseofthevariabilityofsoundoracousticvelocityinwater
will perform satisfactorily.
with changes in temperature, salinity, and depth of water. In
1.4 This standard does not purport to address all of the
addition instability of the equipment can also result in signifi-
safety concerns, if any, associated with its use. It is the
cant errors. For additional information see Practice D 5073.
responsibility of the user of this standard to establish appro-
4.2 Calibration of echo sounding instruments is absolutely
priate safety and health practices and determine the applica-
critical in assuring the adequacy of depth measurements.When
bility of regulatory limitations prior to use.
an echo sounder has been accurately calibrated, any observed
2. Referenced Documents (recorded)depthcanberelatedtothetruedepthofwater.Since
the intended purpose of echo sounding is to measure the “true”
2.1 ASTM Standards:
depth, an independent “true” reference must be used.
D 1129 Definition of Terms Relating to Water
4.3 A bar-check is the most wide-spread, easiest to con-
D 5073 Practice for Depth Measurement of Surface Water
struct, and most economical mechanical method to determine
3. Terminology
corrections for instrument and velocity errors.
4.4 This procedure explains the calibration of a fathometer
3.1 Refer to Terminology D 1129 for terms used in this
or electronic depth sounder using a bar-check.
guide.
4.5 Bar-checking techniques and equipment are general in
3.2 Definitions of Terms Specific to This Standard:
nature and may need to be modified for use in specific field
3.2.1 bar—a section of metallic channel, I-beam, T-beam,
conditions.
pipe, plate, or ball that will reflect sound waves produced by a
fathometer.
5. Apparatus
3.2.2 bar-check—a method for calibrating a fathometer by
5.1 The device used for bar-checking must be a sound-
setting a sound or accoustic reflector (bar) below a survey
reflecting surface that can be lowered to a known depth below
vessel to a known depth below a sounding transducer.
thetransducerofthesurveyvessel.SeeFig.1.Thesesounding-
3.2.3 draft (transducer draft)—the vertical distance from
refecting surfaces (or sounding targets) can be a bar made out
the bottom of the transducer to the surface of the water.
of a section of metallic I-beam or T-beam, pipe, a rectangular
3.2.4 fathometer—An electronic device for registering
section of sheet metal, or a section of metal screen.
depths of water by measuring the time required for the
5.2 Bars used in depths greater than 30 ft (10 m) should be
atleast9in.(23cm)wide.Thedimensionsofthetargetdepend
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This practice is under the jurisdiction of ASTM Committee D19 on Water and
on the type of survey vessel, location of the transducer, and the
is the direct responsibility of Subcommittee D19.07 on Sediments, Geomorphology
and Open-Channel Flow.
Current edition approved Aug. 10, 2003. Published October 2003. Originally
approved in 1998. Last previous edition approved in 1998 as D 6318 – 98.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D6318–03
FIG. 1 Calibration Bar Apparatus
depth
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