Synchronisation system for dating measurements from a sensor (CPi) relative to a reference clock, characterised in that it comprises: - a main unit comprising: ∘ an emulator for emulating an artificial GPS satellite constellation having a time base based on a reference clock, the emulator comprising means for generating (GN, CN1-CN6, SP) for generating a main signal (SgP) on a GPS frequency, simulating all of the emissions of the constellation ∘ processing means capable of delivering a radio signal (SgR) from the main signal (SgP), the processing means comprising frequency conversion means (TMt) able to convert the GPS frequency of the main signal (SgP) to a radio frequency (Fr) ∘ means for transmitting the radio signal (SgR) - a secondary unit (USi) positioned at a distance (Di) from the main unit, comprising: ∘ means for receiving (ERi) the radio signal (SgR) ∘ frequency changing means (TFi) able to convert the radio frequency (Fr) of the radio signal (SgR) to the GPS frequency, in such a way as to deliver a signal that can be used (SgE) by a GPS receiver ∘ a GPS receiver (RPi) comprising: ▪ a local clock (HLi) ▪ slaving means (ASSi) capable of decoding the usable signal (SgE) and of synchronising the local clock (HLi) with the reference clock by means of said decoded information and the distance (Di) ∘ a sensor (CPi) connected to the receiver (RPi), capable of taking measurements and of dating said measurements relative to the local clock (HLi) of the receiver (RPi). - a main unit comprising: ∘ an emulator for emulating an artificial GPS satellite constellation having a time base based on a reference clock, the emulator comprising means for generating (GN, CN1-CN6, SP) for generating a main signal (SgP) on a GPS frequency, simulating all of the emissions of the constellation ∘ processing means capable of delivering a radio signal (SgR) from the main signal (SgP), the processing means comprising frequency conversion means (TMt) able to convert the GPS frequency of the main signal (SgP) to a radio frequency (Fr) ∘ means for transmitting the radio signal (SgR) ∘ an emulator for emulating an artificial GPS satellite constellation having a time base based on a reference clock, the emulator comprising means for generating (GN, CN1-CN6, SP) for generating a main signal (SgP) on a GPS frequency, simulating all of the emissions of the constellation ∘ processing means capable of delivering a radio signal (SgR) from the main signal (SgP), the processing means comprising frequency conversion means (TMt) able to convert the GPS frequency of the main signal (SgP) to a radio frequency (Fr) ∘ means for transmitting the radio signal (SgR) - a secondary unit (USi) positioned at a distance (Di) from the main unit, comprising: ∘ means for receiving (ERi) the radio signal (SgR) ∘ frequency changing means (TFi) able to convert the radio frequency (Fr) of the radio signal (SgR) to the GPS frequency, in such a way as to deliver a signal that can be used (SgE) by a GPS receiver ∘ a GPS receiver (RPi) comprising: ▪ a local clock (HLi) ▪ slaving means (ASSi) capable of decoding the usable signal (SgE) and of synchronising the local clock (HLi) with the reference clock by means of said decoded information and the distance (Di) ∘ a sensor (CPi) connected to the receiver (RPi), capable of taking measurements and of dating said measurements relative to the local clock (HLi) of the receiver (RPi). ∘ means for receiving (ERi) the radio signal (SgR) ∘ frequency changing means (TFi) able to convert the radio frequency (Fr) of the radio signal (SgR) to the GPS frequency, in such a way as to deliver a signal that can be used (SgE) by a GPS receiver ∘ a GPS receiver (RPi) comprising: ▪ a local clock (HLi) ▪ slaving means (ASSi) capable of decoding the usable signal (SgE) and of synchronising the local clock (HLi) with the reference clock by means of said decoded information and the distance (Di) ▪ a local clock (HLi) ▪ slaving means (ASSi) capable of decoding the usable signal (SgE) and of synchronising the local clock (HLi) with the reference clock by means of said decoded information and the distance (Di) ∘ a sensor (CPi) connected to the receiver (RPi), capable of taking measurements and of dating said measurements relative to the local clock (HLi) of the receiver (RPi).