Abstract:The digital photogrammetry for deformation measurement(DPDM) in geotechnical engineering is presented together with a software package developed by the authors. First,DPDM is classified as two types according to target markers or not on the observed object. Three-step image correlation analysis algorithms were proposed specially for the geotechnical material with characteristics of apparent local deformation. Second,the algorithm for image calibration and strain calculation,based on the isoparametric quadrangle method widely used in FEM,is illustrated. Meanwhile,main functions of DPDM software package are introduced,and some key points such as image collection with high resolution,measurement accuracy,and scope of application are discussed. The DPDM technique has been proven to be a powerful tool for observing the progressive and local deformation of granular soil,rock,and concrete in geotechnical engineering. Last,a case study for laterally loaded piles is presented.