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V prispevku predstavljamo rezultate testa ranljivosti geodetskih sprejemnikov GNSS ob namernem motenju signala v frekvenčnem področju L1 tehnologije GPS (angl. Global Positioning System). Preizkusili smo odziv devetih sprejemnikov GNSS različnih proizvajalcev, in sicer Leica Geosystems AG, Trimble Inc. in Javad GNSS Inc. Praktični preizkus je bil zasnovan na statičnih in kinematičnih motnjah signalov. Statične motnje z mirujočim motilnikom na različnih oddaljenostih od sprejemnikov (od 10 do 160 metrov) so trajale večkrat zaporedoma po tri minute. Za kratkotrajne kinematične motnje smo namestili motilnik v vozilo, ki se je testnemu območju približevalo z različnimi hitrostmi. Analiza različnih scenarijev je pokazala, da so motilniki v nekaterih situacijah onemogočili sprejem signalov s satelitov GPS, medtem ko so se sprejemniki na motnje signalov GLONASS odzvali različno. Ker med meritvami julija 2019 Galileo ni deloval kot predvideno, smo v študijo vključili le GPS in GLONASS. Geodetski instrumenti GNSS so se na motenje signala odzvali z zmanjšanjem razmerja med signalom in šumom (angl. signal-to-noise ratio % SNR) in bodisi s popolno nezmožnostjo določitve položaja bodisi z nepravilnim izračunom faznih neznank (inicializacijo) ter posledično nepravilno določitvijo položaja. Vzrok popolne nezmožnosti sprejema signala najbolj pripisujemo bližini motilnika, za nepravilno kodno in/ali fazno določitev položaja pa tudi trajanju motenja. This paper presents the results of a vulnerability test of several geodetic Global Navigation Satellite System (GNSS) receivers in case of intentional signal interference in the frequency L1 for GPS (Global Positioning System). Nine instruments from different manufacturers (i.e., Leica Geosystems AG, Trimble Inc., Javad GNSS) were tested. The test was based on static and kinematic jamming. A static scenario with three-minute interruptions was followed by experiments with a stationary jammer located at distances from 10 m to 160 m from the receivers. For short-term kinematic interference, the jammer was installed in the vehicle, which passed the GNSS instruments at different speeds. An analysis of different scenarios showed that the jammer interrupted GPS but not GLONASS signals in certain situations. Since Galileo was not nominally operational at the time of the July 2019 measurements, only GPS and GLONASS were eligible for the study. The geodetic GNSS instruments reacted to the interruptions with a decreased signal-to-noise-ratio (SNR) and either with a complete inability to determine the code/phase position or with an incorrect calculation of phase ambiguities (initialization), which also affected the quality of the positioning. The proximity of the jammer played the most significant role in the complete inability to receive the signal however, for the incorrect positioning longer duration of jamming was also a reason. |
