## 1 Introduction  
Digitalized archive of cultural relics and artworks has become an important means for their restoration and virtual museum construction thanks to the development of 3D measurement technique. Snow sculpture is an aesthetical form of artwork peculiar to cold regions around the world in winter, as shown in Figure 1, and its cultural value is no less than painting, wood carving, architecture and other artistic expressions [1, 2]. However, when warmed up, these artworks, great displays of the wisdom of their designer artists, will disappear. Snow sculpture can be divided into two categories from the perspective of creation [3]. The first category is designed and constructed according to three-dimensional computer modeling, the 3D data of which is known in advance, meaning that there is no need to measure. The other category is works improvised according to shape and texture of snow billet and combined with surrounding scenes.Similar to other sculptures, they fuse the ideas and inspirations of artists. The category of snow sculpture is unique and needs to measure and record 3D data. Therefore, both snow sculpture designers and management companies want to obtain and store 3D data of each snow sculpture in the computer, thereby making it easy to reproduce the original appearance of snow sculpture through technologies such as 3D movie and 3D printing. Obviously, there is actual demand for 3 Dmeasurement of snow sculpture and its scene reconstruction [2], but relevant research has rarely been carried out. At present, the main methods for 3D measurement of cultural relics and artworks include laser scanning, sequence image method and structured-light vision measurement [4; 5; 6; 7]. Laser scanning is highlyaccuratebut expensive, and its point cloud is not dense enough to adequately describe details. Sequence image method has low requirements for equipment and is easy to operate, but it cannot measure objects without obvious texture (such as pure white porcelain bottles) and has low accuracy. Structured-light vision measurement has the advantages of high accuracy, simple equipment, easy operation and low cost, but the camera is easily affected by illumination. Considering large size, single surface color, complex texture, and low cost of snow sculpture, structured-light vision measurement is more suitable for 3D measurement of snow sculpture. Structured-light sensors need to work in a relatively controlled light environment traditionally [8], so it is usually operated in a room, while measuring outdoors has always been a challenge. However, snow sculpture is directly exposed to the outdoor environment with sunlight, shadows, reflections, and other environmental noise factors everywhere. Night scanning can reduce the noise, but it is adverse to operator's health and work quality in the temperature range of \(-20\)\({}^{\circ}\)C to \(-30\)\({}^{\circ}\)C. 3D laser scanner can perform 3D measurements such as scanning ancient buildings in the day, but its sparse scanning point cloud cannot fully describe the details of snow sculpture. Therefore, we take advantage of a structured-light sensor with a laser as the light source to scan snow sculpture precisely in the field. Moreover, compared to the coding mode, which is mostly used in controlled scenes, the fixed mode structured-light sensor with better anti-noise performance [9] is more applicable for 3D measurement of snow sculpture. It is hard to obtain a higher signal to noise ratio (SNR) even when using a laser projection outdoors, because the intensity of sunlight is usually 2-5 orders of magnitude higher than that of structured-light stripe [8]. The existing methods have not well resolved this problem. For example, Microsoft's Kinect operates difficultly in high ambient light [10]. Modifying the structured-light sensor, such as installing filter or increasing the intensity of the light source, is a method to reduce noise, but it is at the expense of robustness and cost. So many researchers prefer to solve the above problems by digital image processing.