Application of ADCP to Ocean Current Measurement in Gibraltar Port

1. Where is Gibraltar Port?

Gibraltar Port is located at the southern tip of the Iberian Peninsula, at the entrance to the Mediterranean Sea. It is an important strategic and commercial port.

Port Scale and Throughput

The port of Gibraltar has a high level of throughput. It receives all types of cargo, such as petroleum products, general cargo, and containers. Due to its geographical position, it is an important transit point for vessels from the Atlantic Ocean en route to the Mediterranean Sea and vice versa. The annual cargo throughput is very high, with many vessels coming into the port to discharge various cargoes.

Routes and Business

It is a major hub for shipping routes, with several international shipping lines passing through the port. The port is involved in various businesses: bunkering-a ship fueling business, ship repair, and trans-shipment. It is an important link in the global supply chain, facilitating trade between Europe, Africa, and the Middle East.

Port Management and Operation

The port is well-managed in terms of operational efficiency, and it has modern traffic control systems serving in and out of ports, ships. The port authority is responsible for the maintenance of port infrastructure, security, and compliance with international maritime regulations.

Port Facilities

The port has modern facilities like deep-water berths to accommodate big vessels. There are cranes and other cargo-handling equipment to help in the loading and unloading of goods. Storage facilities for various types of cargo, including perishable goods, are also provided with temperature-controlled warehouses.

Channel and Direct Navigation

The port has a well-maintained channel that permits the safe passage of ships. The depth is good enough to handle deep draft vessels. The navigation directly to and from the port is possible. There are clear navigation aids/markers to navigate the ships.

2. Why should we measure the ocean currents in the Gibraltar port?

The measurement of ocean currents in the Gibraltar port is very important. Ocean current data is quite vital for efficient running and management of the port.

Knowledge of the existing patterns helps captains to plan their routes with higher precision for ship navigation. By knowing these, ships can adjust their speeds and courses to take advantage of favorable currents and avoid adverse ones. This is not only a saving on fuel, but also time. For example, when a ship enters a port, the information of the incoming current will allow it to approach the berth much smoother and safer.

Ocean currents come in handy in terms of port operations when deploying the tugboats. Knowing the direction and strength of the currents will be a great help for tugboats in assisting ships in both docking and undocking operations. In addition, regarding moored ship management, the knowledge of currents would help identify proper mooring arrangements to avoid having ships drift about and hit other ships or the port facilities.

Current measurements also play a crucial role in the estimation of sediment transport. The sediment movements around the port area determine the depth of the channels and berths. The measurement of currents will help the authorities to predict sedimentation problems beforehand.

Acoustic Doppler Current Profiler(ADCP) is a more advanced and convenient means of measuring ocean currents compared to traditional methods. It provides real - time and accurate data, which is so valuable in the dynamic environment of a busy port like Gibraltar.

3. How do ADCPs using the Doppler principle work?

The ADCPs work on the principle of Doppler. They emit acoustic pulses into the water column. These pulses interact with particles in the water, like plankton and sediment particles. Because these particles are in motion, the frequency of the reflected sound waves will change due to this motion.

It does so by measuring the differential frequency between emitted and received signals. From these, with the aid of the Doppler equation, the ADCP computes an estimation of velocity-actually of particles, and those represent water current velocities. Using these returned frequency shifts and by determining where along a beam or beam pulse this returning echo originated from, an upwards oriented vessel mounted .

Ship - borne ADCP

In the case of a ship-borne ADCP, the ADCP is installed on a vessel. While the ship is in motion, the ADCP continuously emits and receives acoustic signals; the data acquired from this process is then processed to give the current velocities along the track covered by the ship. The ship can, therefore, measure currents in all other areas of the port by simply traversing across the same.

Fixed ADCP

Fixed ADCPs are mounted in fixed positions within the port, either on the seafloor or attached to a pier. These ADCPs continuously monitor the currents of water at one particular point. Long-term current monitoring can be availed from it, especially around heavy traffic or critical port structure areas.

4. What's required for the measurement of the high - quality of Gibraltar port currents?

For high-quality current measurement in the Gibraltar port, the equipment needs to possess several important characteristics.

Reliable material should be used for the equipment. Due to the harsh marine environment including such factors as corrosion and physical impacts, the durability of the material becomes of primary importance. The size of the equipment should be small in order to provide the possibility to install it easily, especially when space is limited, such as on ships or on crowded piers.

The weight of the ADCP should be light. A lighter device is more suitable for installation on various platforms and can reduce the load on the supporting structures. Low power consumption is another important factor. In a port environment, it is more convenient to use equipment without large power supplies, especially for long-term and continuous measurements.

Another important aspect is cost-effectiveness. The equipment cost should be reasonable to enable large-scale current measurements in the port.

The casing of the ADCP is preferably in titanium alloy. With excellent corrosion resistance, titanium alloy is vital in the salty sea environment. Besides, it is strong yet light and hence it has the requirements for durability and ease of installation.

5. How to Choose the right equipment for current measurement?

Choice of right ADCP equipment depends on the usage it will be put into.

Based on Usage Purpose

Ship-borne ADCP: Good for mobile measurements. Ships fitted with ADCPs can cover big areas of the port and provide current data over different tracks. It is useful for surveying overall current patterns in the port and giving real-time data during ship movements.

Bottom-mounted ADCP: These are suited for fixed-point measurements. These are installed on the seabed and provide continuous data on the currents at a specific location. The bottom-mounted ADCPs are normally deployed near critical port infrastructure, such as berths and channels, for monitoring the local current conditions.

Buoy-based ADCP: The buoy-mounted ADCPs are good to go where it is not possible to install a fixed-bottom or ship-borne ADCP. They can cover open water areas of the port with current measurements. They are also moderately easy to use and maintain.

Based on Frequency

This is another feature for choice. In the case of the Gibraltar port, there are different frequencies available for different water depths. A 600kHz ADCP suits water depths up to 70m. It can be applied in areas not far from the shore or some relatively shallow part of the port. A 300kHz ADCP is appropriate for water depths up to 110m and is able to cover a wider range of depths in the port. In much deeper waters, a 75kHz ADCP will quite adequately serve depths up to 1000m, which thus can be applicable for areas with relatively deeper water like the approach channels to the port.

There are several well - known ADCP brands such as Teledyne RDI, Nortek, and Sontek. However, there is also a recommended Chinese ADCP brand, China Sonar PandaADCP. It is made of all - titanium alloy material, providing excellent durability and corrosion resistance. It also offers an incredible cost - performance ratio. You can find more information on their website: (https://china-sonar.com/).

Here is a table with some well known ADCP instrument brands and models.