This paper considers an approach to solve the structure monitoring problem using an integrated GNSS system and non-metric cameras with QR-coded targets. The system is defined as a GNSS-assisted low-cost vision-based observation system, and its primary application is for monitoring various engineering structures, including high-rise buildings. The proposed workflow makes it possible to determine the change in the structure geometric parameters under the impact of external factors or loads and in what follows to predict the displacements at a given observation epoch. The approach is based on the principle of relative measurements, implemented to find the displacements between pairs of images from non-metric cameras organized in a system of interconnected chains. It is proposed to determine the displacement between the images for different epochs using the phase correlation algorithm, which provides a high-speed solution and reliable results. An experimental test bench was prepared, and a series of measurements were performed to simulate the operation of one vision-based observation system chain. A program for processing the sequence of images in the MatLab programming environment using the phase correlation algorithm was implemented. An analysis of the results of the experiment was carried out. The analysis results allowed us to conclude that the suggested approach can be successfully implemented in compliance with the requirements for monitoring accuracy. The simulation of the vision-based observation system operation with accuracy estimation was performed. The simulation results proved the high efficiency of the suggested system.