ASTM D6318-24
Standard Practice for Calibrating a Fathometer Using a Bar Check Method
- Standard No.
- ASTM D6318-24
- Release Date
- 2024
- Published By
- American Society for Testing and Materials (ASTM) US / ASTM
- Latest
- ASTM D6318-24
- Introduction
Standard Overview and Technological Evolution
The ASTM D6318-24 standard was first published in 1998, revised in 2003, confirmed in 2014, and reinstated in 2024. This standard establishes a standardized process for manually calibrating echo sounders using a bar calibration device, addressing measurement errors caused by variations in water sound velocity.
Core Terminology Analysis
Terminology Definition Application Examples Bar Calibration Calibrating an echo sounder by setting an acoustic reflector (bar) of known depth Using a 23cm wide I-beam as the calibration reference in inland lakes Transducer Draft The vertical distance from the bottom of the transducer to the water surface Ocean survey vessels need to compensate for the 1.2m transducer immersion depth Sound Velocity Profiler An electronic device that directly measures the sound velocity distribution in water Replaces traditional strip calibration in areas with strong currents
Technical requirements for calibration devices
The standard stipulates that the calibration device must meet the following key parameters:
- Material specifications: Metal I-beam/T-beam, steel pipe or metal plate, width ≥23cm when water depth >10m
- Weight range: 20-50kg (adjusted according to water current strength)
- Suspension system: Non-stretching steel cable/chain, scale interval ≤10 feet
Typical case: Yangtze River waterway measurement uses a 40kg steel plate strip device, combined with GPS positioning to ensure vertical alignment.
Key Points of Environmental Condition Control
Condition Parameters Ideal Range Allowable Range Risk Threshold Wind Speed <5mph 5-15mph >15mph Water Depth <30m 30-100m >100m Calibration Frequency 3 times/day 1 time/day Uncalibrated
Standardized Operating Procedure
- Warm Up the Instrument: Start the Echo Sounder and warm it up for 10 minutes
- Initial Setup: Set tide level, draft, etc. to manufacturer's specifications
- Shallow Water Calibration: Lower the bar to 10 feet and adjust the "Draft" parameter
- Deep Water Calibration: Lower to 50 feet and correct the "Sound Velocity" parameter
- Verification Cycle: Repeat steps 3-4 until the error is <1%
- Mid-Point Calibration: Perform verification measurements at 20/30/40 feet
Sound Velocity Profiler Alternative
A sound velocity profiler is recommended when:
- Strong currents causing strip device deflection (>15°)
- Deep-sea measurements in water depths exceeding 100m
- Quick acquisition of vertical sound velocity profile data is required
Note: The sound velocity profiler still needs to be regularly benchmarked using a strip calibration.
Implementation recommendations and error control
Typical error sources and countermeasures:
Error type Correction method Sound velocity stratification effect Establish depth-sound velocity correction table Device is non-vertical Use dual GPS positioning monitoring Sudden temperature change Increase the frequency of noon calibration According to the USACE Hydrographic Survey Specification (EM 1110-2-1003), it is recommended to perform additional calibration in the following situations:
1) Salinity change > 5ppt; 2) Temperature gradient > 2℃/m; 3) The equipment runs continuously for more than 8 hours.
ASTM D6318-24 Referenced Document
- ASTM D1129 Standard Terminology Relating to Water
- ASTM D5073 Standard Practice for Depth Measurement of Surface Water
ASTM D6318-24 history
- 2024 ASTM D6318-24 Standard Practice for Calibrating a Fathometer Using a Bar Check Method
- 2003 ASTM D6318-03(2014) Standard Practice for Calibrating a Fathometer Using a Bar Check Method
- 2003 ASTM D6318-03(2008) Standard Practice for Calibrating a Fathometer Using a Bar Check Method
- 2003 ASTM D6318-03 Standard Practice for Calibrating a Fathometer Using a Bar Check Method
- 1998 ASTM D6318-98 Standard Practice for Calibrating a Fathometer Using a Bar Check Method
