Digital Tape Measurements
As the last technology available for the digital measurement of the human body, has to be mentioned a simple but effective method: electronic tape measurement. The method combines classical human body measurement and digital technology. The measurement process is completely similar to classical tape measurement, where lengths are measured by a tape at different key-location of the human body(chest, waist, sleeve, etc.). The tape device records electronically the measured distances.
3D Body Scan Accuracy
The basic output of a 3D body scanner is a point cloud. A high-resolution scanner produces a more dense point cloud than a low-resolution scanner. High resolution is typically needed if the fingers have to be accurately represented, for instance, for individualized glove design.
3D whole-body scanners available on the market provide scanning accuracy of up to 5 mm according to the manufacturers, example:
- VITUS scanners of up to 1 mm,
- TC2 of up to 3 mm, or Size Stream 3D body scanner of up to 5 mm.
- Multiscanner systems (3dMD scanner) or hand-held scanners (Artec Group scanners)
The reported accuracy may be much better down to a fraction of a millimetre. Nevertheless, these numbers refer to the geometry size, fitting the small view area of such scanners. The actual accuracy of the final 3D scan of the body consisting of the multiple single frames that have to be brought into a common coordinate system and aligned is generally much better. The quality of such spatial alignment strongly depends on the abundance of the geometric features of the scanned object.
Furthermore, the accuracy can be compromised when scanning dark or reflective surfaces or in adverse lighting conditions leading to higher scattering of the point cloud. Incomplete surfaces and scanning artefacts are also often the case especially when scanning complex geometries such as a human body. In narrow spaces such as armpits and crouch the body parts shade each other against the scanner beam, and consequently, prevent some surface area to be scanned. On one hand, this phenomenon can be prevented by setting a posture with legs and arms spread wider than in a standing straight posture, which should minimize body part shading.
The point clouds can be converted to a 3D digital copy of a human with colour and shading effects often called an avatar. The points are connected to triangles (also called a mesh), and this mesh is often reduced to the most essential triangles to cover the information of the shape (Fig. 5àpoint cloud (left), triangulated mesh (middle), and Gouraud shaded (right) head scan.). This means the nose, for instance, has more triangles to cover the shape, than the forehead. These avatars are often used in software for virtual fitting.
The shape of the human head or body can be quantified using principal component analysis (PCA). Generally, the first principal component is related to stature, the second to weight/body mass, and the third is related to relative arm/leg length. However, also posture components may emerge from the PCA, for instance, the amount of lordosis in the back. (Fig.6à Model changes for a principal component related to body mass.)