*1.3. Advantage*

The establishment of a tunnel surface flatness detection system based on threedimensional laser scanning technology is more intuitive and simple to reflect the surface flatness of tunnels. It can provide solid theoretical support and technical guidance for the tunnel engineering construction process thus has very important research significance. It solves the problem that the project in the tunnel does not meet the expectation of future construction guidance and the problem that the existing tunnel engineering initial support flatness detection system is not optimistic. The main innovation of this research is to propose a method for detecting the flatness of the initial support of the tunnel based on the three-dimensional laser scanning technology, introduce the calculation method of the flatness of the initial support of the tunnel, and introduce the concepts of overall flatness and local flatness. The comprehensive analysis of the surface flatness of the initial support of the tunnel through the combination of the overall flatness calculation method and the local flatness calculation method and the flatness distribution diagram has a good guiding role in engineering practice. It also provides research ideas for scholars who study tunnel-related fields [25].
