DJA and MDI first used an electronic theodolite for lines lifting in 2000 for a tall ship conversion and ever since have been developing and improving techniques. A collaboration with GSS and developments in laser scanning hardware and software, has now made full 3D laser scanning of smaller hulls a viable option.

Advantages of laser scanning include:

• Reliable recording of the entire hull surface rather than individual measured sections
• A great reduction in on-site time, keeping slipping costs low or enabling lines lifting between tides
• Increased accuracy, typically 5-10mm over a 15m hull
• A usable 3D computer model ready for further work such as stability analysis or structural alterations.
• Confidence in the accuracy of CAD models by direct comparison to the original scan data

At Stormcats, three monohulls and a catamaran were scanned using a FARO LS880 scanner in a seven hour period on site, collecting some 18 million points per vessel at an accuracy of up to +/-3mm. The dense point cloud was then cleaned and aligned to the required vessel axis, before being used to create a clean IGES surface model of the hull suitable for CAD use.

Continual checking of accuracy against the original scan data allows a clean model with detailed information on the reliability of the data to be created. The computer models will now be used to provide stability information for the model range and also for alternative superstructure moulds to be designed and built to exactly fit the existing hull models.

Laser scanning provides a method to control the accuracy of moulds, build jigs, unit construction and faired hulls, ensuring that built vessels are true to the original CAD design intent, improving quality and performance. The technology has also been used for jumboisation, where a hull can be scanned and the mid-section built to exactly match the existing hull. This can reduce time out of service while the accurate extension is built. Similar use of the technology can be made for repair work.

Other uses for laser scanning includes civil survey work in hard to access areas (tidal areas, underside of bridges), recording of heritage hulls, digitising half models, monitoring erosion, creating 'as built' drawings of complex pipework systems and many more applications outside of marine engineering.

MDI are keen to develop this technology further and the prospects it opens up to operators, builders and owners of all sizes of vessels.