A method for continuously detecting a state of contact or non-contact between a tip of an instrument and a writing surface of a writing medium of variable thickness positioned on a bearing surface of a tracking device; said method comprising the steps consisting in: - determining, at a current instant in time (t i), the position (Pos(t i)) of the tip of the instrument with respect to the bearing surface; - determining, at the current instant in time (t i), a distance (h(t i)) between the bearing surface and the tip, on the basis of said position (Pos(t i)) of the tip; - updating the current value of a minimum distance (h min (ti)) between the bearing surface and the writing surface with the distance (h(t i)) between the bearing surface and the tip at the current instant in time (t i), when said distance (h(t i)) is shorter than the current value of the minimum distance (h min (t i)); - determining, at the current instant in time (t i), a movement parameter (PM(t i)) of the tip, representative of a ratio of the movement tangential to the writing surface to the movement normal to the writing surface between the current instant in time (t i) and the preceding instant in time (t i-1); characterized in that it comprises the steps consisting in: - determining, at the current instant in time (t i), an amplitude parameter (dPos(t i)) representative of the amplitude of the movement of the tip between the current instant in time (t i) and the preceding instant in time (t i-1); - determining a state of contact between the tip and the writing surface, at the current instant in time (t i), when: - the distance (h(t i)) is shorter than or equal to the sum of a minimum current distance (h min) and a tolerance (tol(t i)), said tolerance being representative of an uncertainty regarding the distance (h(t i)) between the writing surface and the bearing surface; - the movement parameter (PM(t i)) is representative of a movement that is essentially tangential to the writing surface, i.e. its value is lower than or equal to a tangential movement threshold; and - a norm of the amplitude parameter (dPos(t i)) is higher than or equal to a minimum amplitude threshold (dPos min); - otherwise determining a state of non-contact between the tip and the writing surface, at the current instant in time (t i). - determining, at a current instant in time (t i), the position (Pos(t i)) of the tip of the instrument with respect to the bearing surface; - determining, at the current instant in time (t i), a distance (h(t i)) between the bearing surface and the tip, on the basis of said position (Pos(t i)) of the tip; - updating the current value of a minimum distance (h min (ti)) between the bearing surface and the writing surface with the distance (h(t i)) between the bearing surface and the tip at the current instant in time (t i), when said distance (h(t i)) is shorter than the current value of the minimum distance (h min (t i)); - determining, at the current instant in time (t i), a movement parameter (PM(t i)) of the tip, representative of a ratio of the movement tangential to the writing surface to the movement normal to the writing surface between the current instant in time (t i) and the preceding instant in time (t i-1); - determining, at the current instant in time (t i), an amplitude parameter (dPos(t i)) representative of the amplitude of the movement of the tip between the current instant in time (t i) and the preceding instant in time (t i-1); - determining a state of contact between the tip and the writing surface, at the current instant in time (t i), when: - the distance (h(t i)) is shorter than or equal to the sum of a minimum current distance (h min) and a tolerance (tol(t i)), said tolerance being representative of an uncertainty regarding the distance (h(t i)) between the writing surface and the bearing surface; - the movement parameter (PM(t i)) is representative of a movement that is essentially tangential to the writing surface, i.e. its value is lower than or equal to a tangential movement threshold; and - a norm of the amplitude parameter (dPos(t i)) is higher than or equal to a minimum amplitude threshold (dPos min); - the distance (h(t i)) is shorter than or equal to the sum of a minimum current distance (h min) and a tolerance (tol(t i)), said tolerance being representative of an uncertainty regarding the distance (h(t i)) between the writing surface and the bearing surface; - the movement parameter (PM(t i)) is representative of a movement that is essentially tangential to the writing surface, i.e. its value is lower than or equal to a tangential movement threshold; and - a norm of the amplitude parameter (dPos(t i)) is higher than or equal to a minimum amplitude threshold (dPos min); - otherwise determining a state of non-contact between the tip and the writing surface, at the current instant in time (t i).