!TERRESTRIAL LASER SCANNING!HUMAN SKULL, JAW AND STAGING BOXES!!!

Thursday 2nd April 2015 0806514

!!!!!!!! !!!!!!!!!!!!EXECUTIVE SUMMARY!!This report outlines the Terrestrial Laser Scanning project and presents its successes and challenges. It also looks at what would have been done differently if performed again.!!The terrestrial laser scan project involved three scans of a human skull from the University of Glasgow Anatomy Department in order to create a three-dimensional model. Patches and pipework were used to model within Leica Cyclone 8.1. The scans took place in lab 142 in the Anatomy Department on Wednesday the 11th March 2015.!!Extruded patches were used for staging boxes and pipe work was used to symbolise box handles.!!It became apparent that a fourth scan was needed to fully cover the object. In hindsight , the use of a handheld laser scanner may have been more appropriate than the Leica C10 scanner. Use of modelling software designed for irregularly shaped objects may also have improved the model.

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Figure 1.1: Station B Setup

Figure 1.3: Gap In Skull Point Cloud

Figure 1.2: 3D Model with Skull and Jaw Point Cloud

Figure 1.4: Spiky Meshed Skull

THE PROJECT!!A human skull and jaw were mounted separately on staging boxes and three scans were taken from different setup locations. One scan from the back of the skull and two from the front that centred on each eye socket. The setup at scan station B is shown in figure 1.1 above. A resolution of 1mm at 2m was used at each setup. The scan stations were setup using 6” HDS targets. Instrument and target heights were observed at each station. The initial project aim was to produce a full 3D model of the scene. However, the irregular shape of the skull and jaw made patching inappropriate and problems were encountered when trying to mesh each object. Final project deliverables included patched and piped box models with cleaned unified skull and jaw point cloud.!!SUCCESS!!Overall the project was successful in producing scans that fit together well when registered. No obvious issues appeared within the scanning process as accurate instrument heights were observed. This made registering the scans easier and produced a well-fitting product. The point cloud exhibited a large amount of noisy data that had to be cleaned. Piping and patching in Leica Cyclone 8.1 was challenging but produced a reasonable product, shown in figure 1.2 above.!!CHALLENGES!!Although the scans were carried out effectively, a fourth scan would have helped fill any gaps that were present. As the project was agreed with the Anatomy department last-minute there wasn’t much time for reconnaissance to plan the setup locations. This combined with a lack of scanning experience led to gaps in the dataset that could have been avoided. Note the gap in the point cloud on the top of the skull shown in figure 1.3 above. Setting the instrument higher may have resolved this but then the detail on the bottom of the skull may not have been observed. Difficulties were encountered in data processing using Leica Cyclone, meshing the skull in particular. Trials were run in separate model spaces to check if a mesh could be created from the skull or jaw data. Firstly, this was done using the scans separately by cleaning each point cloud and attempting each of the three mesh options. However, this proved unsuccessful as each tool created an extremely spiky mesh that was not of sufficient quality. The mesh was so spiky that deleting the spikes and filling the holes was not an option. The best of the trials is shown in figure 1.4 above. Secondly, the scans were unified and the TIN mesh method was attempted but the result was equally as bad so the final product was a clean point cloud of the skull and jaw with patched and piped box models. Patching and piping was difficult as alignment problems were encountered. Unsuccessful attempts were made to align with the reference plane, this might have been easier to do from the start rather than after building the 3D patched model.!!WHAT WOULD BE DONE DIFFERENTLY!!A better product may have been achieved by choosing a simpler shaped object with a less dense point cloud that could have been meshed more easily in Leica Cyclone. However, choosing an irregularly shaped object gave more exposure to tools that Cyclone offers while trying to improve the product and helped highlight some software limitations. Also, a fourth scan station would have filled some of the gaps to improve the final point cloud. Due to the laser footprint of the Leica C10 Scanner a hand scanner may have been more appropriate for the close-range data capture used in this project. Also, in Leica Cyclone the alignment of patches and pipework to the reference plane could have been done at the beginning to make the modelling process easier and give a more aesthetically pleasing final product. However, it was decided to create the model from real points.

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