A navigation system, device and method for assisting a mobile user in navigation. In a preferred embodiment, the device comprises a processing unit configured to execute a navigation program, output peripherals, to provide navigation instructions to the mobile user, the device having access to a satellite radiolocalization module, arranged to acquire the current location, to a map database, containing cartographic information, and to a sensor peripheral; the navigation program being further arranged to generate navigation instructions according to a computed route based on the acquired current location, the cartographic information and a desired destination; the device having a normal operation mode and at least one low-power mode, wherein the navigation device is configured to change mode according to the one or more of the following data: the current location; the computed route; data provided from the sensor peripheral; and by the corresponding method.