A track estimation device configured to estimate a combined cycling and walking track of a cyclist, comprising: a satellite positioning system receiver; a sensor, including at least a triaxial acceleration sensor and a triaxial gyroscope sensor, for providing action information enabling an estimation of an action of the cyclist; a CPU configured to: estimate an action of the cyclist based on the action information from the sensor, the estimated action being one of: being seated (i.e. cyclist is pedalling while sitting on saddle of bicycle), standing (i.e. cyclist is pedalling while standing up from saddle of bicycle), inertial running (i.e. bicycle is travelling by an inertial force while cyclist is not pedalling), and walking (i.e. cyclist is dismounted from bicycle and walking (including walking while pushing the bicycle forward)); determine a reliability of satellite positioning information received from the receiver, wherein the CPU determines the reliability of the satellite positioning information as being high, medium or low; and update a parameter selected based on the estimated action of the cyclist if the reliability of the satellite positioning information is determined to be high, the parameter being a gear value indicating a distance that the bicycle is travelling during one rotation of a crank pedal if the estimated action is being seated or standing, and the parameter being a stride length if the estimated action is walking; estimate the track based on satellite positioning information received from the receiver if the reliability of the satellite positioning information is high, or estimate the track at least partially based on dead reckoning using the updated parameter if the reliability of the satellite positioning information is medium or low (S704-S707). a satellite positioning system receiver; a sensor, including at least a triaxial acceleration sensor and a triaxial gyroscope sensor, for providing action information enabling an estimation of an action of the cyclist; a CPU configured to: estimate an action of the cyclist based on the action information from the sensor, the estimated action being one of: being seated (i.e. cyclist is pedalling while sitting on saddle of bicycle), standing (i.e. cyclist is pedalling while standing up from saddle of bicycle), inertial running (i.e. bicycle is travelling by an inertial force while cyclist is not pedalling), and walking (i.e. cyclist is dismounted from bicycle and walking (including walking while pushing the bicycle forward)); determine a reliability of satellite positioning information received from the receiver, wherein the CPU determines the reliability of the satellite positioning information as being high, medium or low; and update a parameter selected based on the estimated action of the cyclist if the reliability of the satellite positioning information is determined to be high, the parameter being a gear value indicating a distance that the bicycle is travelling during one rotation of a crank pedal if the estimated action is being seated or standing, and the parameter being a stride length if the estimated action is walking; estimate the track based on satellite positioning information received from the receiver if the reliability of the satellite positioning information is high, or estimate the track at least partially based on dead reckoning using the updated parameter if the reliability of the satellite positioning information is medium or low (S704-S707). estimate an action of the cyclist based on the action information from the sensor, the estimated action being one of: being seated (i.e. cyclist is pedalling while sitting on saddle of bicycle), standing (i.e. cyclist is pedalling while standing up from saddle of bicycle), inertial running (i.e. bicycle is travelling by an inertial force while cyclist is not pedalling), and walking (i.e. cyclist is dismounted from bicycle and walking (including walking while pushing the bicycle forward)); determine a reliability of satellite positioning information received from the receiver, wherein the CPU determines the reliability of the satellite positioning information as being high, medium or low; and update a parameter selected based on the estimated action of the cyclist if the reliability of the satellite positioning information is determined to be high, the parameter being a gear value indicating a distance that the bicycle is travelling during one rotation of a crank pedal if the estimated action is being seated or standing, and the parameter being a stride length if the estimated action is walking; estimate the track based on satellite positioning information received from the receiver if the reliability of the satellite positioning information is high, or estimate the track at least partially based on dead reckoning using the updated parameter if the reliability of the satellite positioning information is medium or low (S704-S707).