## 1 Introduction  
The concept of \"Industry 4.0\" introduces the future trends in industrial development, and the growing interest in intelligent manufacturing has highlighted the need to research novel methods in large-scale metrology [1; 2]. Integration of advanced measurement instruments with traditional technologies is recognized as an effective approach to achieve the prospection. Dimensional metrology in manufacturing, which is an important factor for quality insurance, has the characteristics of large measurement range, requirements for high precision and efficiency, and strong environmental interference. In recent years, the breakthroughs in optical technologies and low-cost, fast computers stimulated the wide use of laser tracker and photogrammetry systems. They both provide abundant solutions for three-dimension coordinate measurement [3; 4; 5]. A laser tracker is based on length measurement by interferometer and angle measurement by encoder. Leica AT series and Faro Vantage series are representatives in this field of research. With sophisticated environmental parameter compensation, they can gain an accuracy of 15 um + 6 um/m and a measurement frequency of up to 1000 Hz. The measurement range is about 80 m. In most cases, it is seen as the benchmark in metrology and gives compensation to positioning error in other instruments [6; 7]. However, the laser tracker has its limitations. Firstly, it only conducts single target measurement each time and the efficiency is relatively lower. For example, in large aircraft leveling, hundreds of points on the whole fuselage need to be measured, which may take one or more days. It is time-consuming and unacceptable. Secondly, in a large-scale space, a multi-station network is often necessary for full coverage of the measurement zone. The measurement error is prone to accumulate during coordinate system transformation and distance increase. The system performance will be affected to a great degree [8; 9]. Close-range photogrammetry experienced a revolution at the beginning of the 2000s [10] and it has been widely used in applications ranging from automobile manufacturing to aerospace [11; 12; 13; 14; 15]. Monocular vision and binocular vision are common solutions for positioning and orientation in large-scale metrology and they enjoy an accuracy of submillimeter. Nevertheless, limited by the image processing and matching algorithm, photogrammetry methods have a relatively lower measurement frequency, which leads to unideal dynamic measurement capacity. Even worse, photogrammetry systems have strict requirements for the environment and measured objects. Light flection from the surface of objects, such as aircraft skin and body-in-white, may lead to low image quality and match failure [16]. In the past few years, we have also witnessed the rapid development of stationary distributed measurement network and it is now widely used in aircraft manufacturing, digital shipbuilding, and tooling monitoring. The workshop measurement positioning system (wMPS) is a representative composed of transmitters, photoelectric receivers, signal processors, and a terminal computer. Each transmitter contains a rotation head and a static base, as shown in Figure 1.  
Two line-laser modules are embedded in the rotation head with an intersection angle of 90\({}^{\circ}\). The head rotates about the z-axis of the local coordinate system at a speed of 1500-3000 rev/min. In the static base synchronization lasers are in circular distribution and they will shine when the rotation head goes across the pre-defined reference point in the encoder. The receiver at the measured point obtains the synchronization signal and record it as the start time. After that, laser module 1 and 2 will scan over the receiver in turn. The time difference between synchronization signal and scanning signals is captured through precise timing. It is in a linear relationship with two scanning angles. In this way, the spatial relationship between the transmitter and receiver can be determined solely.