Image Quality Evaluation of Target Surface in The Subgrade Settlement Monitoring System

The accuracy of the detection in the image-based subgrade settlement monitoring system depend on the quality of the collected spot image, This paper studies the main factors affecting the quality of spot images and propose a method for quality assessment of spot image without reference. The method analyze the characteristics of the spot change under the influence of external conditions, and reflect the change effect of the spot feature through the size, brightness, edge definition and contrast of the spot image.Then,the four evaluation factors are integrated into one. Through the experiment, the spot images under the influence of the target surface are collected. The spot image obtained by the experiment is evaluated using the non-reference spot image evaluation method proposed in this paper, and verifies by measuring the center position of the spot image. The experimental results show that the spot image is affected by different influencing factors, this evaluation method method can combine various influencing factors to reflect the change of image quality,and can give reasonable evaluation results for spot images that are affected to varying degrees. It provides theoretical and experimental basis for the actual subgrade surface settlement monitoring system.