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Topographical Survey In Monrovia, Liberia

Read about how we helped align marine navigation markers to allow ships to enter the port at night / in poor visibility.

Article By: Tom Ayre | Last Update: November 2020


Pharos Marine / Port Of Monrovia


Survey – 2 Weeks
Draughting – 3 Days


Monrovia, Liberia


Tom Ayre / Chris Horton

Our Client

THS Concepts were appointed by Hampton based Pharos Marine who supply and design a range of marine navigation equipment. Large ships need a lot of space to turn and operate in, the equipment Pharos Marine provide essentially allows ships to safely navigate into and around the port.

The Required Work

The Freeport of Monrovia is an important freight terminal in Liberia, West Africa. This busy port handles over 90% of the imports into Liberia, so it’s an important piece of infrastructure!

Navigation towers (leading lights) are an essential element of port operations: they allow ships to safely navigate into the port at night. The port’s towers are built approximately 250m from each other and the principal concept is that the towers should align when a ship is on the correct course travelling into the port. 

The issue that we had to solve was that the existing towers had been built at an incorrect angle. As a result, the ships travelling in would have had to travel through the port’s breakwater – which obviously could not happen. In fact, the navigation tools were so flawed that no ships entered the port at night!

The Solution

THS Concepts were tasked with undertaking a topographical survey of the existing navigation towers and marker buoys entering the port. The initial survey of these items was to check how far out of alignment everything was. Working alongside Pharos Marine, we calculated that the navigation towers were significantly out of alignment and had to be re-built! They were approximately 8 degrees off of the line they should have been on. 8 degrees may seem insignificant, but the port stretches 1.5 km, so it equated to a big error.

The towers alignment meant that the ships would have technically had to navigate through the port’s breakwater, which obviously wouldn’t have worked.  Luckily, the navigation buoys were positioned okay in relation to the navigation channel.

Once we knew the position that the new towers had to be placed, we got to work setting out the new tower’s foundations and steelwork.


With the new navigation towers in place, the port can now safely operate at night! This would be an extremely beneficial event for the port, which serves as the main hub into the country of Liberia. We were very proud to have completed this project, having ships coming into the port 24 hours a day would have certainly boosted trade figures for the country!

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