**5. Digital graphical demonstrations**

Similarly, Gorey Pierhead in Jersey was also saved from destruction (it also had failed in 1964, **Figure 6**, Ref. [10], Vid [1]) using LiDAR techniques to make the digital models that helped to demonstrate the need for intervention and to secure funds to enable the preservation of the pierhead of the breakwater and jetty.

Photographic merges and videos of the pierhead at low tide (with Gorey Castle in the background) showed the size of the loose granite masonry structure and where'bulging' of masonry and loss of concrete foundations were exposed (**Figure 7**). The pierhead itself show in **Figure 8** had to be rebuilt in 1964 after a major storm failure shown from the archives in **Figure 6**. To understand the evolution of the structure from the original pre-1620 pier, a LiDAR survey accurately captured the geometry of the whole of the pier in 2009. There was another major storm event in 2011 and a second LiDAR survey was taken, and the Point Cloud data overlaid on the GPS referenced coordinates of the original 2009 survey. **Figure 7** shows graphically the super imposed LiDAR scans to show where there was a "bulge" outwards of the masonry and a loss of concrete at the base.

#### **Figure 6.**

*Collapse of Pierhead in 1965 (archives), Ref. [9].*

#### **Figure 7.**

*Digital models overlaid 2 years apart. Localised masonry movements highlighted. Screen shot graphic colour. Ref. [9]. (Link to video materials is available at the end of the chapter).*

I have used this image widely in several engineering papers and conferences because the overlay of LiDAR models (with an accuracy of 2 mm) superimposed upon one another two years apart is self-explanatory. The second survey was directly after a severe storm and significant concerns by the structures' custodians were raised as some areas of visible physical movement had taken place. The model *Digital Technology to Preserve Heritage Structures DOI: http://dx.doi.org/10.5772/intechopen.99023*

#### **Figure 8.**

*Gorey Pierhead and breakwater at low tide. Gorey Castle in background (digital photo merge), Ref. [10].*

was able to demonstrate that one small area was 'bulging' out of the page (red in x, y, z coordinates indicates out of the page movement) and at the base concrete had been lost from the foundation apron (blue in x, y, z coordinates indicate in to the page movement). Just as importantly, the model graphic was able to clearly demonstrate that the damage was in two areas only because most of the pierhead and breakwater had remained in place after the storm (green overlay of the two sets of x, y, z coordinates have no distance). This meant that for the custodians (the Ports of Jersey) no very high costs were involved for the whole breakwater and only localised strengthening was requiring funding.
