Method for monitoring an outdoor space, termed monitored space, using a system comprising: a. a monitoring computer network comprising means for sending/receiving in a frequency band between 135 MHz and 175 MHz (135.10 6 to 175.10 6 Hertz) in a non-simultaneous bidirectional mode and the geographical coverage of which is equal to or greater than that of the monitored space; b. a portable device (351, 352, 450) comprising a satellite positioning chip and means for sending and receiving information on the monitoring computer network; c. computer means connected to the monitoring computer network and comprising, in memory means, a georeferenced map of the monitored space and a virtual geofencing of a monitoring area, the geographical area of which is contained within the geographical range of the sending/receiving means of the monitoring computer network, and display means enabling the monitored space to be viewed; said method comprises the steps consisting in: i. using virtual geofencing to delineate a monitoring area on the georeferenced map; ii. using the portable device to send, on the monitoring network, at regular intervals, a frame of information comprising an individual identifier of said portable device, the geolocated position of this portable device and the distress state of said portable device; iii. recording the geolocated position of said device and the timestamp of this position in the memory means of the computer system; iv. displaying, on the display means of the computer means, the position of the portable device on the map when the distress state transmitted by the portable device corresponds to a dangerous situation; characterized in that it comprises the steps consisting in: vi. storing, in a history file, the geolocation of the detected distress situations; vii. using virtual geofencing to delineate, in the monitoring area, an area, termed risk zone, depending on the records contained in the history file. a. a monitoring computer network comprising means for sending/receiving in a frequency band between 135 MHz and 175 MHz (135.10 6 to 175.10 6 Hertz) in a non-simultaneous bidirectional mode and the geographical coverage of which is equal to or greater than that of the monitored space; b. a portable device (351, 352, 450) comprising a satellite positioning chip and means for sending and receiving information on the monitoring computer network; c. computer means connected to the monitoring computer network and comprising, in memory means, a georeferenced map of the monitored space and a virtual geofencing of a monitoring area, the geographical area of which is contained within the geographical range of the sending/receiving means of the monitoring computer network, and display means enabling the monitored space to be viewed; i. using virtual geofencing to delineate a monitoring area on the georeferenced map; ii. using the portable device to send, on the monitoring network, at regular intervals, a frame of information comprising an individual identifier of said portable device, the geolocated position of this portable device and the distress state of said portable device; iii. recording the geolocated position of said device and the timestamp of this position in the memory means of the computer system; iv. displaying, on the display means of the computer means, the position of the portable device on the map when the distress state transmitted by the portable device corresponds to a dangerous situation; vi. storing, in a history file, the geolocation of the detected distress situations; vii. using virtual geofencing to delineate, in the monitoring area, an area, termed risk zone, depending on the records contained in the history file.