1. A method for processing pose data derived from an absolute pose of an elongate object having a tip, said method comprising: a) placing said tip on a plane surface with an invariant feature that is tangible and whose position is defined in world coordinates parameterized by world coordinate vectors (X o ,Y o ,Z o ) where X o is a Cartesian x-axis, Y o is a Cartesian y-axis and Z o is a Cartesian z-axis, said Cartesian axes intersecting at a world origin (0,0,0); b) measuring said absolute pose optically from on-board said elongate object with an optical arrangement mounted at a top end of said elongate object and using said invariant feature in a pose recovery technique comprising geometric invariance, said absolute pose comprising measured values of parameters (φ,θ,ψ,x,y,z) representing Euler rotated object coordinates parameterized by object coordinate vectors (X,Y,Z) with said parameters (φ,θ,ψ) being Euler angles defining an orientation of said elongate object with respect to Cartesian axes X o , Y o , Z o of world coordinates (X o ,Y o ,Z o ), and with said parameters (x,y,z) being the position of a point on said elongate object expressed in said world coordinates with respect to said world origin (0,0,0); c) preparing pose data corresponding to said absolute pose; d) identifying a subset of said pose data; and e) transmitting said subset to an application.