A method for obtaining a refined pose for a 3D sensor for online 3D modeling of a surface geometry of a surface of an object, said pose encompassing six degrees of freedom,DOF, including three translation parameters and three orientation parameters, the method comprising: providing said 3D sensor, said 3D sensor being adapted to capture 3D point measurements of said surface of said object from a viewpoint; providing a geometry model of at least part of said surface built from a set of previously captured 3D point measurements; providing at least one target on said object; providing a target model for said object, wherein said target model comprises information extracted from at least the position of previously observed targets among said at least one target provided on said object; observing a portion of said surface of said object with said 3D sensor including observing at least one currently observed target and less than three currently observed targets and capturing currently captured 3D point measurements; matching said at least one currently observed target with a corresponding matched target of said previously observed targets using said target model to obtain partial positioning constraints, said partial positioning constraints constraining less than said six degrees of freedom and constraining said three translation parameters, at least one remaining parameter not being thereby constrained; generating at least one missing initialization parameter (612, 912) for an initialization pose by attributing a value for said at least one missing initialization parameter, said value obtained after sampling said at least one missing initialization parameter space wherein the at least one missing initialization parameter (612, 912) is generated from said previously observed targets, each said at least one missing initialization parameter corresponding to each of said at least one remaining parameter; obtaining said initialization pose from said partial positioning constraints and said at least one missing initialization parameter (606, 914), said initialization pose encompassing said six degrees of freedom; finding a best fit arrangement of said currently captured 3D point measurements in said geometry model using said initialization pose, said finding said best fit arrangement including using each sampled at least one missing initialization parameter and selecting a converging best fit arrangement; generating said refined pose for said 3D sensor using said best fit arrangement. providing said 3D sensor, said 3D sensor being adapted to capture 3D point measurements of said surface of said object from a viewpoint; providing a geometry model of at least part of said surface built from a set of previously captured 3D point measurements; providing at least one target on said object; providing a target model for said object, wherein said target model comprises information extracted from at least the position of previously observed targets among said at least one target provided on said object; observing a portion of said surface of said object with said 3D sensor including observing at least one currently observed target and less than three currently observed targets and capturing currently captured 3D point measurements; matching said at least one currently observed target with a corresponding matched target of said previously observed targets using said target model to obtain partial positioning constraints, said partial positioning constraints constraining less than said six degrees of freedom and constraining said three translation parameters, at least one remaining parameter not being thereby constrained; generating at least one missing initialization parameter (612, 912) for an initialization pose by attributing a value for said at least one missing initialization parameter, said value obtained after sampling said at least one missing initialization parameter space wherein the at least one missing initialization parameter (612, 912) is generated from said previously observed targets, each said at least one missing initialization parameter corresponding to each of said at least one remaining parameter; obtaining said initialization pose from said partial positioning constraints and said at least one missing initialization parameter (606, 914), said initialization pose encompassing said six degrees of freedom; finding a best fit arrangement of said currently captured 3D point measurements in said geometry model using said initialization pose, said finding said best fit arrangement including using each sampled at least one missing initialization parameter and selecting a converging best fit arrangement; generating said refined pose for said 3D sensor using said best fit arrangement.