Topographical Survey / Setting Out At The Port Of 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
Tom Ayre / Chris Horton
THS Concepts were appointed by Pharos Marine to undertake an topographical survey of 2 navigation towers at the Freeport of Monrovia, and the setting out/realignment of the navigation towers, which had been built incorrectly. 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.
Our problem 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!
To start with, Chris and Tom surveyed the existing, incorrectly-built towers. 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 current tower alignment meant that the ships would have technically had to navigate through the port’s breakwater which obviously isn’t ideal.
Looking over the previous surveying companies’ notes we discovered that the company had used hand-held compasses to set out the works! We weren’t filled with confidence in the integrity of the previous surveyors!