# Three-Dimensional Human Head Reconstruction Using Smartphone-Based Close-Range Video Photogrammetry
## 1 Introduction  
Three-dimensional modeling of the human head has a wide range of applications. Three-dimensional data of the head, with extension to the whole body, are widely used in clinical, industrial, anthropological, forensic, sports, commercial, and entertainment areas. Medical applications of 3D scanning may be divided into four groups: epidemiology, diagnosis, treatment, and monitoring [1, 2]. The 3D measurements can benefit cranial deformation studies [3, 4, 5, 6], diagnosis, craniofacial information analysis [7], and evaluation of the effects of orthotic helmets [8]. Models and 3D visualizations allow measurements to be performed for planning a surgical intervention, assess surgical outcomes, measure changes after surgeries, forecast the result of a facial plastic/cosmetic surgery, document clinical cases, compare pre-treatment and post-treatment models [9], perform more accurate orthodontics diagnoses [10], and achieve better dental reconstruction results [11]. In biomedical engineering, anthropometrical measurements help to design prosthesis [12] and allow for the rapid prototyping of customized prostheses. The manufacturing of medical products has to be based on population anthropometrical studies so that medical equipment perfectly suits the physical characteristics of patients [13]. Head 3D modeling may be used for the documentation of research, registering EEG electrode positions [14, 15, 16], collection of anthropometric data [17, 18, 19, 20, 21], and defining normal head parameters [22]. Non-medical fields of 3D head modeling applications include computer animation, movies and animation, security, teleconferences, and virtual reality, forensic identification [23],behavior research (perceptions of attractiveness), identifying human facial expressions, and sculpture [24]. Another large group of applications are found in industry: design of headwear products, such as helmets, headgear, glasses, and headphones [25; 26]; optimization of wearable product comfort and function [27; 28; 29], perform better ergonomic design of human spaces, simulate the wearing of clothes [30; 31], and create products that take into account ergonomics [27; 32], model and predict respirator size and fit [25; 33; 34]. There are several types of imaging techniques to create 3D models: laser line systems [35], structured light systems [36], close-range photogrammetry [37; 38; 39], and radio-wave-based image capturing systems [40]. Image-based reconstruction and modeling of scene [41; 42; 43], objects [44] and processes [45; 46] is a widely accessible technique in terms of price for gathering information [1; 47; 48]. The complexity of usage of such technologies mostly depends on algorithms and user interface design. Three-dimensional objects may be reconstructed by fitting mathematical models to the collected image data [49; 50]. However, the model is required, and it should be adequate to represent a range of variations the modeled object may possess. Therefore, the most popular technique for estimating three-dimensional structures from two-dimensional image sequences is Structure from Motion (SfM) [51; 52; 53; 54]. The means of object modeling that is easily accessible to ordinary users is based on handheld devices, such as smartphones [55; 56]. Smartphone-based close-range digital photogrammetry would be the desired way for modeling objects at home. Photogrammetry using ordinary consumer-grade digital cameras can provide a cost-effective and sufficiently accurate solution for creating 3D models of the head as new smartphones come equipped with higher quality cameras. The most common application of head modeling for home users could be the acquisition of head anthropometric data in order to select the appropriate size of headwear products. The other application could be trying out head apparel. The construction process of the head 3D model for the home user must be fully automatic. The software tool is only allowed to give the user simple directions to correct their actions if they lead to a model of unsatisfactory quality.