Technical Specifications of Offshore Visibility Monitoring Equipment and Surface Wind Monitoring Equipment
Technical Specifications of Offshore Visibility Monitoring Equipment
Based on Subsection 2.1 Section II of the National Technical Regulations on Oceanographic Observations issued with Circular 08/2021/TT-BTNMT, the technical specifications for offshore visibility monitoring equipment are stipulated as follows:
2.1.1. Technical Specifications
Unit of measurement: meters (m)
Measurement range: 10 meters and above
Resolution: 1 meter
Measurement error is specified in Table 1.
Table 1. Offshore Visibility Measurement Errors
| No. | Visibility Range | Measurement Error |
|---|---|---|
| 1 | Less than or equal to 600 m | ± 20 % |
| 2 | Greater than 600 m and less than or equal to 1500 m | ± 10 % |
| 3 | Greater than 1500 m | ± 20 % |
2.1.2 Offshore Visibility Monitoring by Manual Method
a) Offshore visibility levels are based on focal points specified in Table 2.
Table 2. Offshore Visibility Levels Based on Focal Points
| Visibility Level | Farthest Visible Focal Point (m) |
Nearest Invisible Focal Point (m) |
| 0 1 2 3 4 5 6 7 8 9 |
< 50 50 200 500 1000 2000 4000 10000 20000 50000 |
50 200 500 1000 2000 4000 10000 20000 50000 > 50000 |
b) Requirements for grading offshore visibility levels are specified in Table 3.
Table 3. Offshore Visibility Levels Based on Meteorological Phenomena
| Visibility Characteristics | Offshore Visibility (m) |
Grading Scale | Meteorological Phenomena |
| Very Poor | 0 to < 50 50 to < 200 200 to < 500 |
0 1 2 |
Very dense fog Dense fog Moderate fog |
| Poor | 500 to < 1000 1000 to < 2000 |
3 4 |
Light fog Very heavy rain or haze or moderate smoke |
| Moderate | 2000 to < 4000 4000 to < 10000 |
5 6 |
Heavy rain, light haze (or smoke) Moderate rain or light haze (or smoke) |
| Good | 10000 to < 20000 | 7 | Light rain or no rain |
| Very Good | 20000 to < 50000 | 8 | No rain |
| Exceptional | Above 50000 | 9 | Completely clear sky (crystal clear) |
Technical Specifications of Surface Wind Monitoring Equipment
Based on Subsection 2.2 of this section, the technical specifications for surface wind monitoring equipment are as follows:
Table 4. Specifications for Surface Wind Measurement Columns
| No. | Type of Wind Measurement Column | Stainless Steel Material | Diameter (mm) |
Thickness (mm) |
Height (m) |
Auxiliary Equipment |
|---|---|---|---|---|---|---|
| 1 | Round Column | Round steel | ≥ 49 | ≥ 3 | 10 to 12 | Lightning protection device, guy cable, tensioner, nut |
| 2 | Triangular Column | Round steel | ≥ 36 | ≥ 3 | 10 to 12 | Lightning protection device, guy cable, tensioner, nut |
| 3 | Guyed Column | Round steel | ≥ 15 | ≥ 3 |
When the meteorological garden is 1500 to 2000 meters or more away from the wave observation position and the height of the meteorological garden's surface is more than 10 meters above the average sea level, wind observations must be conducted at the wave observation position.
Respectfully!
