Vision metrology with a single camera is applied to slope displacement detection. A camera configuration to meet the required measurement precision, sensitivity and reliability is looked for. The paper derives related statistical expressions and compares alternative camera configurations, which can detect 2mm displacements per 30m length. Evaluation is experimentally executed by use of a 1/30 scale model of a typical construction site of a slope with an idealistc targeting condition. The configuration of four exposures at each of three stations is proved to match the three criteria above.