The invention relates to a system for estimating the spatial position (pose) of a tool (2) within an object (1 ), particularly in the form of a human bone that is to be machined with said tool, comprising: a sensor (21 ) being designed to be coupled to said tool (2), which sensor (21 ) is further designed to generate an sensor output signal (31 ) upon machining of said object (1 ) along an actual trajectory (30), which sensor output signal (31 ) depends on a material property of said object along said actual trajectory (30), an analyzing means being designed to determine a correlation between said sensor output signal (31 ) upon machining said object (1 ) and a plurality of pre-determined candidate output signals (42), each candidate output signal (42) being generated in beforehand using said material property along an associated model trajectory (40) in a model of said object (1 ), and wherein said analyzing means is designed to estimate a spatial position of the tool (2) within the object (1 ) using the model trajectory (40) whose associated candidate output signal (42) has the highest correlation with the sensor output signal (31 ), for instance. The invention further relates to a method for estimating the pose of the tool (2), as well as a computer program product
