There is provided an imaging unit comprising at least one image sensor, a measuring instrument including at least one marker, a position computing unit, a determining unit, and an output controller, wherein the imaging unit is configured to acquire an image comprising a user and the marker, and provide the acquired image to the position computing unit, wherein the position computing unit is configured to compute a position ofthe marker with respect to the user based on the image provided by the imaging unit, and further provide the computed position to the determining unit, wherein the determining unit is configured to determine whether the computed position of the marker matches a retrieved measurement position, and further output the result of the determination to the output controller, and wherein the output controller is configured to provide an indication when the marker position matches the measurement position.提供包括至少一個影像感測器之一成像單元、包含至少一個標記之一測量儀器、一位置計算單元、一判定單元及一輸出控制器，其中該成像單元經組態以獲取包括一使用者及該標記之一影像，且將該所獲取影像提供至該位置計算單元，其中該位置計算單元經組態以基於由該成像單元提供之該影像而計算該標記相對於該使用者之一位置，且進一步將該所計算位置提供至該判定單元，其中該判定單元經組態以判定該標記之該所計算位置是否匹配一所擷取測量位置，且進一步將該判定之結果輸出至該輸出控制器，且其中該輸出控制器經組態以在該標記位置匹配該測量位置時提供一指示。
