Abstract: This paper develops new methods to detect the adjusting parameters for digital image distortion,and to determine the elements of interior orientation of cameras.The mean square errors of photo coordinate is lower than 2.5 pixels.A new manner of digital photo geological logging and its principle are introduced,so is a practical system developed by the authors.This paper also discusses the geometric precision of photo geological logging for tunnels.Theory and practice prove that the precision of photo logging can be effectively controlled by use of a digital orientation-camera based on a normal digital camera,that digital orthophotomosaic obtained from original photos can be used as logging base-map,and that photogrammetry based on a normal digital camera can also be used to measure geological elements of attitude of layers.