The invention relates to a self-contained detector (100) for measuring a physical quantity, which includes: at least one sensor (105) for sensing a value representing a physical quantity; a geolocation means (110), configured to provide geolocation coordinates of the detector; an emitter (145) of a wireless signal representing each detected value and the determined coordinates; and a self-contained electric power source (120) configured to power the detector, each sensor, the geolocation means, the emitter and the power source being embedded in a flexible, shock-resistant shell (125), and in a sealed shell (130).