Topographical & Setting Out Survey Previous Project
Learn about our topographical and setting out surveys at the Port of Monrovia, Liberia
Article By: Tom Ayre, Director
The navigation towers are an essential element of port operations: they allow ships to safely navigate into the port at night. The 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 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. The navigation tools were so flawed that no ships entered the port at night!
Undertaking the Topographical Survey
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 like insignificant, but the port stretches 1.5 km so it equated to a big error. Looking over the previous surveying companies’ notes it was 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!
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Undertaking the Setting Out Survey
Following the survey, it was time to prepare suitable locations for the realignment to take place. Calculating where the new towers were to be placed involved surveying the existing navigation buoys as well as the extent of the harbour opening. This was an interesting experience, travelling on a boat that looked like it could sink at any moment… Once the existing layout of the port had been established it was time to start setting out the new foundations. The port employed a Liberia-based building company to dig out, construct the shuttering and pour the new foundations. As you can expect, the health and safety attitudes we adhere to in the Western World haven’t yet appeared in mainstream Liberia… No shoes, employees cutting and binding electricity cables themselves, working 18 hours a day etc…
Once the foundations had been dug, it was time to orientate and level the tower base that was concreted into the foundations. It was crucial that this too was set to the correct orientation and level to ensure that the triangle points on the towers aligned with each other correctly. We worked right up to our limit and were within minutes of having to leave as our plane back home was shortly leaving! Luckily with approximately an hour to spare we managed to get the towers aligned and level. We left it up to the Liberians to finish the foundations! Overall the project went very well, it was carried out on time and the essential task of aligning the towers was done correctly.