## 1 Introduction  
In the automotive, aerospace, cultural heritage, and medical industries, there are many potential benefits of creating three-dimensional (3D) digital models of existing objects. This technique is known as reverse engineering (RE). It can be defined as the process of generating an identical Computer-Aided Design (CAD) model using an existing physical object. This model can then be utilized in several downstream applications such as prototyping, testing and verification [1], simulation, drafting, design improvement, customization in medicine, etc. It is particularly useful when an existing CAD model is not available, the component becomes outdated, or the design requires modification in addition to reconciling broken geometry, reducing product development time, or minimizing the manufacturing costs, etc. The RE process is based on the following two basic steps: (1) data acquisition and (2) surface reconstruction. Depending on the application requirement or the desired accuracy, different techniques or methods may be used to accomplish these steps. The accuracy of the final CAD model is dependent both on the data acquisition technique, as well as the surface reconstruction procedure. Indeed, the effectiveness of a given step in the RE process always relies on the accuracy achieved in the preceding step. It means that the accuracy of the surface reconstruction is dependent on the precision that can be attained during data acquisition. Hence, the data acquisition process controls the accuracy of the subsequent steps in the RE process. Unsuitable data acquisition results in inaccurate data and complicates future steps, thus making the RE ineffective and inefficient. Therefore, it is crucial for the designers to select the appropriate data acquisition, depending on the application requirements. The different techniques for data acquisition can be classified into contact and non-contact methods as shown in Figure 1. The main purpose of the 3D data acquisition is to collect and record object information pertaining to shape and dimensions either using touch probes (contact) or optical systems (non-contact). In the contact method, a probe makes contact with the object's surface, while in the non-contact approach, there is no physical contact with the object's surface. Non-contact methods are based on different techniques including photogrammetry [2], triangulation and time of flight [3], as well as utilize various light sources such as laser and white light [4]. In the last decade or so, 3D optical scanning technologies have been identified as the most efficient and effective data acquisition methods used for RE [7]. These systems can deliver the desired accuracy  
Figure 1: Classification of data acquisition techniques [3; 5; 6]. CT: computed tomography; MRI: magnetic resonance imaging. for large, complex sheet metal parts and dyes used in the automotive industry. As a result of their inherent benefits, different types of 3D optical scanners with varying specifications and capabilities have been developed. Recently, the handheld scanners based on laser and white light have been amongst the favored digitization technologies. Handheld 3D scanners are preferred over non-transportable alternatives by researchers and industries owing to their low weight and greater portability. They generate 3D surfaces using a triangulation mechanism in which either the laser or white light is projected onto an object, and the distance between the scanner and the object surface is measured through the triangulation. The acquired points are then used to create a CAD model in the appropriate program. A new type of handheld scanner has become available with self-positioning systems that depend on positioning targets placed on the scanning object [8], in addition to the many different existing types of handheld scanners (based on different techniques) available for data acquisition. Due to the wide variety of available scanners, it is often difficult for the user to select a suitable scanner for their application.