HIGH-ACCURACY GROUND SURFACE DISPLACEMENT MONITORING

Developments in automated close range photogrammetry over the past dec ade have produced systems capable of achieving measurement accuracies of one part in several hundred thousand of the size of the object. The impetus for precision photogrammetry has come mainly from the industr ial sectors of aircraft, aerospace and antenna manufacturing, but pote ntial applications are not limited to these areas alone. This paper di scusses the applicability of industrial photogrammetric techniques for the monitoring of ground surface displacements which accompany oil re covery operations. A pilot study is reported in which photogrammetric positioning accuracies at the millimetre level were sought over an are a of 1 x 1.6 km. The large scale of the convergent network, coupled wi th the high level of positioning accuracy, meant that special consider ation had to be given to both operational aspects (helicopter photogra phy and targeting) and mathematical modelling (refraction compensation ). Lessons learned in this project have implications for the broader a pplication of high precision phologrammetry in large scale civil and g eotechnical engineering, as well as in the mining industry.