Infrastructure engineering needs to rely on accurate data. Unfortunately, outdoor AR is generally not sufficiently robust and accurate for engineering users to rely on for their work. As a solution, we have proposed an alternative method that consists of augmenting digital twins of city environments in the form of 3D photo-realistic meshes obtained from drone photos. In addition of providing guaranteed accuracy and robustness, our augmentation method can be used off-site, during the night or in areas covered with snow.