A behavior of a walker is detected according to combination of detection of the walking behavior on a level and an altitude variation of the walker to more accurately detect the behavior of the walker. A burned calorie can be obtained according to the type of the walking behavior. An altitude variation can be obtained more accurately by integrating altitude variation only at sections with vertical movement during walking. A stride is estimated according to the behavior of the walker in consideration of the vertical movement. Obtained position and traveling direction are used for compensating values in inertial navigation system. The behavior with and without vertical movement is used in a walker navigator and a worker observing system including a worker terminal carried by the walker for detecting the behavior of the worker and a worker observing terminal for providing the detected position and behavior of the walker.