A system for detecting GNSS signal jammers to be positioned on a roadside, the system comprises: a first device for receiving a GNSS signal; a second device that is configured to measure at least one characteristic of a received GNSS signal and to detect, on the basis of at least one characteristic, interference in the GNSS signal caused by a jamming signal; a third device for triggering the capture of an image of the road if the GNSS signal is subject to interference caused by a jamming signal, the first device configured to receive, via a radio link, a sequence of a satellite radionavigation signal received by a vehicle and retransmitted by the vehicle to the system via the radio link.