2169-3536 (c) 2018 IEEE. Translations and content mining are permitted for academic research only. Personal use is also permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2018.2879718, IEEE Access VOLUME XX, 2017 1 Date of publication xxxx 00, 0000, date of current version xxxx 00, 0000. Digital Object Identifier 10.1109/ACCESS.2017.Doi Number GNSS Spoofing Detection Using Single- Antenna Based on Measuring the Altitude of the Victim Above Sea Level Larisa Dobryakova 1 , Łukasz Lemieszewski 2 , Evgeny Ochin 3 1 West Pomeranian University of Technology, Faculty of Computer Science and Information Technologies 49 Żołnierska St., 71-210 Szczecin, Poland, +48 694 977 954, ldobryakova@wi.zut.edu.pl 2 The Jacob of Paradies University, Department of Technology, 25 Teatralna St., 66-400 Gorzów Wielkopolski, Poland, +48 602 341 143, llemieszewski@ajp.edu.pl 3 Maritime University of Szczecin, Faculty of Navigation, 1–2 Wały Chrobrego St., 70-500 Szczecin, Poland, +48 608 437 562, e.ochin@am.szczecin.pl Corresponding author: Evgeny Ochin (e-mail: e.ochin@am.szczecin.pl). ABSTRACT The spoofing organization is as follows: the GNSS signal generator transmits a signal simulation of several satellites at the GNSS frequency. If the level of the simulated signal exceeds the signal strength of real satellites, the GNSS receiver will "capture" the fake signal and calculate the position based on it. All receivers that fall into the spoofing zone will calculate the same coordinates, while the receivers located in different places will have a slight mismatch in time. The interference can be done away with - such interference simulates the movement of the receiver along the path defined by the spoofer. Receiver of GNSS signals determine the XYZT coordinates. Suppose that the receiver has a built-in clock, the accuracy of which is comparable to the accuracy of the clock of GNSS, i.e. in the framework of this article, we abstract from the need for correction of T. For a ship, only the XY coordinates are significant, so we will focus only on the calculations of the XY coordinates and the Z coordinate is used only to detect of a spoofing. INDEX TERMS antispoofing, antiterrorism, sea level measurement, single-antenna receivers, spoofer, spoofing detection algorithm, transport safety I. INTRODUCTION Satellite-based navigation remains the predominant navigation solution for both commercial and military applications. However, proven threats to GNSS from jamming, spoofing, and environmental blockages have convinced the military, as well as many commercial technology firms, that now is the time to find new navigation solutions that can enhance GNSS. Receiver of GNSS signals determine the XYZT coordinates. Suppose that the receiver has a built-in clock, the accuracy of which is comparable to the accuracy of the clock of GNSS, i.e. in the framework of this article, we abstract from the need for correction of T. For a ship, only the XY coordinates are significant, so we will focus only on the calculations of the XY coordinates. It is necessary to emphasize that we use a conventional satellite antenna, that is, the problem of practical implementation of spoofing detection is reduced only to programming. The strategy of escaping spoofing is as follows. A developed spoofer simulates GNSS signals in such a way that at the moment of the victim’s capture, the false coordinates coincide with the real ones and then simulate the movement of the receiver along a certain trajectory [1-3]. II. SOME NOTATION AND DEFINITIONS    (, ) – known sea level at the point (, ) of the sea or ocean.    → {  ,  ,  },  = ,       – satellites of GNSS, N – the number of visible satellites.  Spoofing – an attack on a GNSS, in an attempt to deceive the GNSS receiver by transmitting powerful false signals that mimic the signals from the true GNSS, exceeding the power of these true signals.  Spoofer – complex computer and radio equipment for the implementation of GNSS spoofing.  {  ,  } – coordinates of the spoofer (  =).  {  ,  } – victim's coordinates, as measured by the spoofer (  =).