Offshore Physical Environmental Guidelines
Appendix C - Monitoring Equipment Specifications

Table C-1 - Monitoring Equipment Specifications

Accuracy Specifications Collection Specifications[1]
Sensor Accuracy Sensor Requirements Averaging Intervals Recording Intervals
Wind Speed ± 1 kt up to 20 kts
± 5% for speed > 20 kts

- resistance to icing[2]
- capability to digitally estimate 10-minute and 2-minute averages (preferable vector averages)
- operation over full temperature range (for region in which equipment used)
- capability to digitally estimate 1-minute and 1-hour averages (preferably vector averages)
Suggested:
- digital output (real time or archival) capability

1 minute (suggested)
2 minute
10 minute
1 hour (suggested)
10 minutes
(10 minute average, hourly otherwise)
Wind Direction ± 5 degrees As per wind speed As per wind speed As per wind speed
Pressure ± 0.1 hPa (barometer reading)
± 0.2 hPa (sea level pressure[3])
± 0.01 hPa (QNH altimeter setting)

- capability to display 3-hour time trace required for tendency characteristic
- operation over full temperature range (for region in which equipment installed[4])
Suggested:
- digital output (real time or archival) capability

Instantaneous 1 minute
Air Temperature ± 0.1 degrees Celsius - operation over full temperature range (for region in which equipment used)
Suggested:
- digital output (real time or archival) capability
1 minute 1 minute
Humidity (wet bulb) ±  0.1 degrees Celsius - operation over full temperature range (for region in which equipment used)
Suggested:
- digital output (real time or archival) capability
1 minute 1 minute
Cloud Height ± 10 m up to 100 m
± 10% from 100 m to 300 m
± 20% for above 300 m
- operation over full temperature range (for region in which equipment used)
Suggested:
- digital output (real time or archival) capability
1 minute 1 minute
Cloud Amount 1 okta (1/8th of the sky) if instrumentation is in use - operation over full temperature range (for region in which equipment used)
Suggested:
- digital output (real time or archival) capability
1 minute 1 minute
Visibility ± 50 m up to 500 m
± 10% from 500 m to 1500 m
±  20% for beyond 1500 m if measured by instrument
- operation over full temperature range (for region in which equipment used)
Suggested:
- digital output (real time or archival) capability
1 minute 1 minute
Wave Height ± 3% for periods 2 to 20 s
±  6% for periods 21 to 30 s

- operation over range 0 to 30 m
- recording interval between 17.5 and 35 minutes
- continuous recording interval height criteria reached
- digital output (real time or archival) capability

Combined Significant Wave Height
   20 minutes
Maximum Wave Value
   20 minutes
Wave Spectral Period
   20 minutes
Wave Spectra
   20 minutes
Combined Significant Wave Height
   20 minutes
Maximum Wave Value
   20 minutes
Wave Spectral Period
   20 minutes
Wave Spectra
   20 minutes
Wave Direction(s) ± 5 degrees - recording interval between 17.5 and 35 minutes
- continuous recording interval height criteria reached
- digital output (real time or archival) capability
   
Sea Surface Temperature ± 0.5 degrees Celsius - operation over range of -2oC to 25oC 1 minute 1 minute[5]
Water Level 0.01 metre - digital output (real time or archival) capability
- operation over full temperature range (for region in which equipment used)
10 minutes 1 hour
Water Temperature ± 0.5 degrees Celsius - digital output (real time or archival) capability
- operation over full temperature range (for region in which equipment used)
  No longer than ½ hour for moored measurements, and monthly (preferably) or seasonally for CTD profiles
Salinity ± 1 part per thousand - digital output (real time or archival) capability
- operation over full salinity range (for region in which equipment used)
  No longer than ½ hour for moored measurements, and monthly (preferably) or seasonally for CTD profiles
Depth ± 0.2 metre - digital output (real time or archival) capability
- operation over full depth range (for region in which equipment used)
  No longer than ½ hour for moored measurements, and monthly (preferably) or seasonally for CTD profiles
Ocean Currents: horizontal current speed and direction ± 0.02 m/s for range 0-3 m/s
± 5o for range 0-360o
- record at near-surface, mid-depth and near-bottom depths
- apply averaging intervals of at ≥ 5 minutes
  No longer than ½ hour
Heave, pitch and roll As provided Equipment provided by the Operator    

[1] Sensor model/serial number, sensor height, siting description, record specification, trip report (if required), local chart datum (if required), equipment data sheet.
[2] Resistance to icing means "continued operation during light to moderate icing conditions."
[3] Derived pressure readings depend on parameters additional to the barometer reading, including temperature readings and height of the barometer above mean sea level.
[4] Barometers may not be exposed to the full range of temperatures that an installation may experience if installed in a heated area.
[5] Recording and averaging intervals for obtaining sea surface temperatures will require further discussion. This is attributed to past history, the overall design of an offshore installation and the effectiveness of measuring temperature from an installation or standby vessel.

OCEANOGRAPHIC

Mooring Considerations

Moorings or deployments should be maintained in one location for as long as possible and need not be moved with every relocation of an Installation in a particular area. Consideration should be given to mooring or deployment longevity rather than relocation, whenever possible. Both the location and design of the moorings or de ployment should be included in the Program Description described in Section 1.2.

The wave measuring instrument should be located so that the wave field being measured is not disturbed by the Installation and located sufficiently close to the Installation so that reliable communications between the wave instrument and the receiver on the Installation are maintained. The instrument should also be located so that the wave field being measured is not substantially altered from that at the site of the Installation because of sheltering, bottom effects, etc., or in general have a different exposure to prevailing conditions.

ICE MANAGEMENT

Instruments for ice detection and monitoring primarily include radar, which are generally operated from a drilling unit, ship, or aircraft. Instruments should be selected to optimize performance in a number of areas, including: range, target size detection and detection of small ice masses, detection in poor weather and sea conditions, and target tracking. In situ measurements of above-surface iceberg size are generally obtained using camera or sextant. Sonar and other underwater equipment, ROV or AUV, are generally used for draft measurement.

The Operator is encouraged to discuss existing or potential instrument and detection and measurement technologies with other operators and ice service groups to ensure that the most appropriate tools are used.

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