Water Level Measurement
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Uses of a Tide Staff & Gauge
- The reductions of soundings. Tidal observations are to be carried out for the full period when a ship is deployed to the survey area.
- For predicting tidal characteristics & updating ANTT Observations. Obs should be carried out over at least 32days using a precise gauge.
6 uses of Tide Staff & Gauge info & data
- Shipping Movements
- Tide Tables
- Definition of Coastlines
- Flood & Storm Warnings
- Mean Sea Level
Criteria when considering a suitable site for a Tide Staff
- Stability of site
- Stability of structure
- Stability of water column
- Proximity to benchmarks
- Proximity to power/phones
- Ease of access
- Minimum exposure to Tidal Ranges
- Minimum exposure to tidal stream/current
- Minimun exposer to waves
- Minimum siltation
- Minimum marine growth
- Protection from vandalism
- Avoid restricted entrances
4 Types of Tide Gauges
- 1. Floatation Types
- 2. Acoustic Types
- 3. Pressure Types - Electronic Types
- 4. Radar
Floats upon the surface & heights are determined by RTK & wave action is removed through low pass filters.
The water level is measured by sending an acoustic pulse down a small pipe within the environmental tube.
Gas (Bubbler gauge) Open/Closed: gas, usually nitrogen, is emitted from a submerged tube at a constant rate. Fluctuations in the hydrostatic pressure due to changes in the tidal height modify the emission rate of reading.
- The changes in pressure are detected by a sensor immersed in the water and converted by an electrical signal.
- In these systems the sensor may be a crystal transducer, stain gauge or other transducer.
Measure the change in sea level by monitoring the time-of-flight if a radar pulse from the sensor to the sea surface and back to the unit.
4 Main Tidal Records
- Summary of Checks on Automatic Tide Gauge - F_03_05_AA217185
- H148 - Record of Tidal Readings
- Record of Tidal Observations - F_05_ALL_AA217190
- Tide Gauge Deployment Log - F_03_05_AA217170
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