1. A method for obtaining three-dimensional surface points of an object in an object coordinate system, comprising: providing a set of target positioning features on said object, each of said target positioning features being provided at a fixed position on said object, said object coordinate system being defined using said target positioning features, said target positioning features being provided by one of a set of external fixed projectors projecting said features and fixedly secured features; in a first group of steps: acquiring at least a pair of 2D first images of said object by at least a pair of cameras, at least a first portion of said set of target positioning features being apparent on said pair of first images, each said pair of said 2D first images being acquired from a corresponding first pair of viewpoints referenced in a sensing device coordinate system; using an electronic chip in communication with said at least said pair of cameras for implementing the steps of: extracting, from said 2D first images, at least two first sets of 2D positioning features from a reflection of said target positioning features of said first portion on said surface; calculating a first set of calculated 3D positioning features in said sensing device coordinate system using said first sets of 2D positioning features; computing first transformation parameters for characterizing a current spatial relationship between said sensing device coordinate system and said object coordinate system, by matching corresponding features between said first set of calculated 3D positioning features in said sensing device coordinate system and a set of reference 3D positioning features in said object coordinate system, said reference 3D positioning features being cumulated from previous observations; transforming said first set of calculated 3D positioning features into a first set of transformed 3D positioning features in said object coordinate system using said first transformation parameters; cumulating said first set of transformed 3D positioning features to provide and augment said set of reference 3D positioning features; in a second group of steps: providing a projected pattern on a surface of said object using a pattern projector; acquiring at least a pair of 2D second images of said object by said cameras, said projected pattern and at least a second portion of said set of target positioning features being apparent on said pair of second images, each said pair of said 2D second images being acquired from a corresponding second pair of viewpoints referenced in said sensing device coordinate system; wherein said first portion of said set of target positioning features and said second portion of said set of target positioning features being one of the same, partly the same or different; using said electronic chip for implementing the steps of: extracting, from said 2D second images, at least one set of 2D surface points from a reflection of said projected pattern on said surface, and at least two second sets of 2D positioning features from a reflection of said target positioning features of said second portion on said surface; calculating a set of 3D surface points in said sensing device coordinate system using said set of 2D surface points; calculating a second set of calculated 3D positioning features in said sensing device coordinate system using said second sets of 2D positioning features; computing second transformation parameters for characterizing a current spatial relationship between said sensing device coordinate system and said object coordinate system, by matching corresponding features between said second set of calculated 3D positioning features in said sensing device coordinate system and said set of reference 3D positioning features in said object coordinate system; transforming said set of 3D surface points into a set of transformed 3D surface points in said object coordinate system using said second transformation parameters.