# Evaluating the Vulnerability of Several Geodetic GNSS Receivers under Chirp Signal L1/E1 Jamming  
[PERSON]  
1 Faculty of Maritime studies and Transport, University of Ljubljana, Cesta pomorsSakov 4, 6320 Portoroz, Slovenia; [EMAIL_ADDRESS] (M.B. ); [EMAIL_ADDRESS] (F.D.) [PERSON]  
1 Faculty of Maritime studies and Transport, University of Ljubljana, Cesta pomorsSakov 4, 6320 Portoroz, Slovenia; [EMAIL_ADDRESS] (M.B. ); [EMAIL_ADDRESS] (F.D.) [PERSON]  
2 Faculty of Civil and Geodetic Engineering, University of Ljubljana, Jamova cesta 2, 1000 Ljubljana, Slovenia 2 [EMAIL_ADDRESS]; Tel. : +386-1-4768-631 2020 202  
They also stress that the impact of jamming is often not clear for users. Since jammers can cause great damage, it is important to recognise their influence on the operation of different instruments, especially those that play a crucial role in establishing the fundamental infrastructure connected to assisted navigation or positioning. In today's geodesy, the GNSS presents a primary source for the establishment and maintenance of fundamental geodetic infrastructure, which is based on Continuously Operating Reference Stations (CORS). The establishment of CORS networks started in the mid-1990s. During the last two decades, the demand for the optimal continuous functioning of CORS has increased significantly. The optimal functioning of CORS networks is one of the major concerns since (a) modern geodetic coordinate systems rely on a time series of the determination of coordinates [4], and (b) they must provide users with corrections to improve their precision for every specific moment of a day. CORS also support three-dimensional positioning in autonomous driving using high accuracy localisation based on techniques such as differential real-time kinematic (RTK) or precise point positioning (PPP) [5; 6; 7]. Such techniques require good signal reception, both at base stations and on users' receivers, to achieve positioning accuracy within a few centimetres. Since permanently installed GNSS receivers at stations have been able to provide continuous monitoring of changes in position, they have also started to serve geophysical and geodynamics applications. Several GNSS processing strategies have been introduced to minimise positioning errors for estimations of the various impacts of the GNSS, for example, zenith tropospheric and ionospheric delay, which can be used beyond positioning applications. Such products are useful in meteorology for short-term weather prediction [8; 9], space weather monitoring [10; 11; 12] and other geophysical applications, including seismic applications [13]. To meet the basic required needs of geodesy and the geosciences, the CORS infrastructure consists of stations equipped with GNSS receivers, which collect data from at least one, though usually multiple, navigations systems (GPS (Global Positioning System), GLONASS (Russian: Globalnaya Navigatsionnaya Sputnikovaya Sistema), Galileo, BeiDou (Chinese: Beidou Weixing Dohang Xitong)/COMPASS, SBAS (Satellite-Based Augmentation System), QZSS (Quasi-Zenith Satellite System), IRNSS (Indian Regional Navigational Satellite System)). The widespread use of real-time positioning requires additional communication links between a reference and rover receiver. This can result in the GNSS infrastructure being vulnerable to natural impacts (extreme Sun events), multipath and interference caused by unintentional or intentional degradation of the signal, as well as on the communications links. This paper, however, focuses on the impact of GNSS jamming, while real-time communication problems are not considered. Contrary to natural perturbations, the degradation or replacement of the GNSS signal should be the greatest concern. Non-intentional degradation can happen in areas within radars or amateur radios that share the same GNSS bands. Their static position makes them identifiable by interference monitoring systems [14; 15].