In photogrammetry system, the Base-Distance Ratio, the Image Scale, and the Image Standard Error, which construct the network strength of the system, are the main accuracy factors. In this paper, the normal and convergent network configurations of the photogrammetry are studied and the Network Strength, which presents the strength and accuracy of the camera station network, is expressed with the accuracy factors mentioned above. In order to verify the validation of this expression, the large-scale 3D reference field is designed and used to test the effects of these accuracy factors. The experimental results show that the relationship between the accuracy and the factors is consistent with the expression. These conclusions will guide the photogrammetric work to reduce the system errors.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.