Loose combination is a simple SINS/GNSS combination application method. In this way, SINS and GNSS work independently, and the combination algorithm fuses the data and gives the optimal results, and finally feedback to the SINS. This combination method can provide better navigation results than GNSS or SINS alone.
In satellite navigation, all satellites are synchronized at a very high precision. Each satellite transmits the signals containing the data called ephemeris which can be used to compute the precise satellite position. By computing the signal transit time, any user on the earth surface can compute the distance from satellite. Knowing distance and locations of four such satellites, user can compute location by trilateration. The satellite position computed using ephemeris is highly precise whereas using almanac an approximate position can be obtained. The validity of ephemeris is only 2 hours and almanac can be used for longer duration up to few months. User location in the form of latitude, longitude and altitude can be computed using a small device called “receiver”. The device can be embedded into laptops or mobile phones.
ISRO had also developed a Geo Augmented Navigation System called GAGAN which is currently supported by GPS to assist the navigation of Civilian air traffic within Indian Airspace. Once the IRNSS & GAGAN are fully operational , they will help with precise navigation, provide data on mountainous, oceanic areas & enhance security tremendously .The vast spectrum of services that would be provided by the network will be significant to the growth of the Nation in the field of science and space technology which would propel our economic growth in the years to come. The more satellites that
In May 2007, the EU has adopted a new space policy officially acknowledging the potential military use of Galileo satellite navigation system; a step calling for greater attention to the security and defence aspects of the project. In 2001, the then United States (U.S.) Deputy Secretary of Defence Paul Wolfowitz’s letter (see appendix I) to the defence ministers of the European Union (EU) member states demanded the abandonment of the project. This aroused worldwide interest in the security and defence implications of the Galileo system which has been developed as a civil system under civil control as opposed to the U.S. Global Positioning System (GPS) and the Russian Global'naya Navigatsionnaya Sputnikovaya Sistema (Global Orbiting Navigation Satellite System - GLONASS) both of which are sponsored and managed by military authorities. Alongside its anticipated commercial and social benefits to the EU and its citizens, Galileo has also a strategic value for Europe. The EU affirms that this alternative satellite navigation system is being developed not only for the sake of competitiveness, growth, job creation, better transportation across Europe and new services that would improve the daily life of its citizens, but also for attaining such a critical infrastructure of this scale and capability that will strengthen Europe’s independence, competitiveness and influence in world affairs. (EC, 2002a, EC, 2002b, GPS World, 2007, EC, 2007a)
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Different modes of transportation seek the need of GNSSS technology such as rail transport, aviation, under water surveying, marine transportation and surface transportation. In rail transport, GNSS is used in conjunction with other technologies in order to locate rail cars, maintenance equipment. Thus by knowing the precise location of the rail equipment, the probability of occurrence of accidents can be reduced, safety and customer service can be increased. In marine transportation, GNSS is used to determine the accurate position of ships when they are in open sea or in some congested ports. In aviation, GNSS is used for aircraft navigation from departure to landing and mainly for collision avoidance. In surface transportation, vehicles are being equipped with navigation displays for enhancing the efficiency and driver safety. Thus, almost every mode of transportation finds its use from GNSS technology.
This work presents a contribution to the understanding of the ionospheric triggering of L-band scintillation in the region over São Paulo state in Brazil, under high solar activity. In particular, a climatological analysis of Global Navigation Satellite Systems (GNSS) data acquired in 2012 is presented to highlight the relationship between intensity and variability of the total electron content (TEC) gradients and the occurrence of ionospheric scintillation. The analysis is based on the GNSS data acquired by a dense distribution of receivers and exploits the integration of a dedicated TEC calibration technique into the Ground Based Scintillation Climatology (GBSC), previously developed at the Istituto Nazionale di Geofisica e Vulcanologia. Such integration enables representing the local ionospheric features through climatological maps of calibrated TEC and TEC gradients and of amplitude scintillation occurrence. The disentanglement of the contribution to the TEC variations due to zonal and meridional gradients conveys insight into the relation between the scintillation occurrence and the morphology of the TEC variability. The importance of the information provided by the TEC gradients variability and the role of the meridional TEC gradients in driving scintillation are critically described.
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Abstract—This paper formulates a simple vector integral expression for electromagnetic waves received after scattering from a surface. The derived expression is an alternative to the Stratton-Chu equation frequently used for polarimetric surface scattering. It is intended for use in polarimetric Global Navigation Satellite System (GNSS) ocean remote sensing, or any type of polarimetric remote sensing from surfaces, when the surface roughness pattern is known from simulation or data. This paper is intended to present a complete accounting of the steps leading to the simpler vector integral expression. It therefore starts with the scalar case, using Maxwell’s equations and Green’s theorem. It principally treats the case of a transmitter within the integration volume, but discusses how the formalism changes if the transmitter is outside of the integration volume, as with plane waves. It then shows how the scalar expression can be extended to a vector expression for the component of the electric field in an arbitrary receive-polarization direction due to scattering from a rough surface of an incident wave with an arbitrary transmit polarization. It uses the Kirchhoff, or tangent-plane, approximation in which each facet on the ocean is considered to specularly reflect the incoming signal. The derived vector expression is very similar to that for a scalar wave, but it includes all vector properties of the scattering. Equivalence is demonstrated between the Stratton-Chu equation and the derived, simpler expression, which is operationally easier to code than the Stratton-Chu equation in many modeling applications.
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Global navigation satellite systems (GNSS) offer posi- tioning and timing services for an increasing variety of applications (e.g., car and ship navigation, but also syn- chronization of electrical grid stations). GNSS signals are subject to various security attacks, aiming ultimately at disrupting or altering these applications . In this paper, we focus on the spoofing attack, where an attacker (AT) transmits a signal with the purpose of inducing a false spe- cific location estimate to the victim receiver (VR). This attack is active as it requires a transmission by the spoofer. Positioning is typically obtained by measuring the time of arrival of pilot signals known at the receiver. The AT generates and transmits the pilots with proper delays
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Monitoring of engineered structures using geodetic methods has become a prime concern due to its precision, portability and most importantly non-destructive or non- disturbance nature of the technique. The application of this technique was initiated by Teskey and Porter (1988) using integrated geodetic measurement and finite element model to monitor large concrete structures. From their work, new approach was successfully demonstrated and proved that it is possible to determine the structural deformation behaviour when loading are applied. Furthermore, advancement in geodetic instrumentation such as motorised theodolite makes it possible to evaluate structures such as bridges (Katowski, 1995). Until recently, the Global Navigation Satellite Systems (GNSS) technology, specifically the Global Positioning System (GPS) developed by the United States is becoming a leading technology used in structural monitoring (Ogaja, et al., 2007).
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monitoring, etc. In India also, GPS is being used for numerous applications in diverse fields like aircraft and ship navigation, surveying, geodetic control networks, crustal deformation studies, cadastral surveys, creation of GIS databases, time service, etc., by various organizations. The Navigation Satellite Timing and Ranging Global Positioning System (NAVSTAR GPS) developed by the U.S. Department of Defense (DoD) to replace the TRANSIT Navy Navigation Satellite System (NNSS) by mid-90’s, is an all-weather high accuracy radio navigation and positioning system which has revolutionised the fields of modern surveying, navigation and mapping. For every day surveying, GPS has become a highly competitive technique to the terrestrial surveying methods using the odolites and EDMs; whereas in geodetic fields, GPS is likely to replace most techniques currently in use for determining precise horizontal positions of points more than few tens of km apart. The GPS, which consists of 24 satellites in near circular orbits at about 20,200 Km altitude, now provides full coverage with signals from minimum 4 satellites available to the user, at any place on the Earth. By receiving signals transmitted by minimum 4 satellites simultaneously, the observer can determine his geometric position (latitude, longitude and height), Coordinated Universal Time (UTC) and velocity vectors with higher accuracy, economy and in less time compared to any other technique available today.
Abstract. Observations from the South African TrigNet global navigation satellite system (GNSS) and vertical total electron content (VTEC) data from the Jason-1 satellite were used to analyze the variations in ionospheric electron density profiles over South Africa before and after the severe geo- magnetic storms on 15 May 2005. Computerized ionospheric tomography (CIT) was used to inverse the 3-D structure of ionospheric electron density and its response to the magnetic storms. Inversion results showed that electron density signif- icantly increased at 10:00 UT, 15 May compared with that at the same period on 14 May. Positive ionospheric storms were observed in the inversion region during the magnetic storms. Jason-1 data show that the VTEC observed on de- scending orbits on 15 May significantly increased, whereas that on ascending orbits only minimally changed. This find- ing is identical to the CIT result.
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Abstract. This paper reviews the development of the global navigation satellite system (GNSS) radio occultation (RO) observations assimilation in the Global/Regional Assimila- tion and PrEdiction System (GRAPES) of China Meteoro- logical Administration, including the choice of data to as- similate, the data quality control, the observation operator, the tuning of observation error, and the results of the obser- vation impact experiments. The results indicate that RO data have a significantly positive effect on analysis and forecast at all ranges in GRAPES, not only in the Southern Hemisphere where conventional observations are lacking but also in the Northern Hemisphere where data are rich. It is noted that a relatively simple assimilation and forecast system in which only the conventional and RO observation are assimilated still has analysis and forecast skill even after nine months integration, and the analysis difference between both hemi- spheres is gradually reduced with height when compared with NCEP (National Centers for Environmental Prediction) analyses. Finally, as a result of the new on-board payload of the Chinese FengYun-3 (FY-3) satellites, the research status of the RO of FY-3 satellites is also presented.
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Satellite navigation systems are already very popular with motorists, and have implications for safe and green driving. Many functions of modern satellite navigation systems take considerably longer to complete and require more glances compared to conventional controls and displays (such as headlights and windscreen wipers, or visually checking the speed and fuel gauge). A series of related studies (Antin, 1993; Dingus et al., 1989; Wierwille et al., 1991) attempted to assess the visual attentional demand of moving-map displays relative to other in-car tasks. General conclusions were that navigation tasks and displays place higher demands on attention than do conventional (as measured by total glance duration, single glance times, and number of fixations). However, it was also found that drivers adapt to changes in driving demand by altering their scan patterns, suggesting that there may be enough spare capacity to operate a navigation display (Antin, 1993). Dingus et al. (1989) suggested some design improvements to reduce the demand of navigation displays (and hence their impact on the driving task). These were primarily aimed at improving the availability of information on the displays, to be more compatible with
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The results of calculations are shown in Fig. 6. The satellites constellation plots are shown in polar coordinates ρ, θ. The value ρ is defined as follows: ρ = 90 − α where α ∈ [0, 90] is the angle of the satellite elevation above the local horizon. The values θ ∈ [0, 360] is the satellite location azimuth in projection to the local horizon. Angles are measured in degrees. The direction to the north corresponds to the ordinate axis, the east direction corresponds to the abscissa axis. The coordinates origin corresponds to the zenith position of the satellite α = 90 (ρ = 0). Low satellites (α ≈ 0) are located on a circle of the radius close to 90 degrees. The plots show the position of GPS and GLONASS satellites at 12:00 UTC on June 10, 2017, n = 19. The value of m is chosen 9 just for the sake of illustration. Selected satellites are marked with crosses. The left part of the figure shows a constellation corresponding to the non-optimal choice of the first m satellites (x 0 1 = · · · = x 0 9 = 1, x 10 0 = · · · = x 0 19 = 0). In this case, the PDOP cost function is ϕ(M 0 ) = 4.112.
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As misalignment angle calculation needs at least three stars’ information, analy- sis is carried out in the case of three, four and five stars. In these different cases, the maximum misalignment angle calculation errors are less than 1, 3 and 2 mi- cro radians, respectively. The maximum misalignment angle calculation errors of roll, pitch, and yaw axis are less than 1, 1, and 3 micro radians, respectively. Although the error of yaw axis is larger than the other two axes, it is still small enough. And the results are pretty stable. Table 3 shows the detailed simulation results. These results demonstrate that the misalignment modeling using stars and calculation are more accurate than using landmarks, which confirms the statement as mentioned above, as the accuracy of star position is higher than 0.1 milliarcseconds and the accuracy of star centroid extraction is higher than that of landmarks. In the face of the challenges in image navigation brought by three-axis stabilized attitude control mode in geostationary orbit, star navigation is indispensable.
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Nowadays, reconﬁgurable antennas are being used in distinct areas like Internet of Things (IoT) applications, wireless network security, cognitive radio, mobile and satellite communications. The development of wireless communication systems also increases rapidly, hence it is necessary to provide small size and multiband antennas for IoT applications. IoT will provide a platform to allow big data transfer mechanism and communication between people and devices, which provide high quality of life in society . IoT is a worldwide network that provides a platform allowing big data transfer and connection between people and things. To acquire good communication, the antennas connecting to IoT are needed to be small, cost-eﬀective, energy eﬃcient to operate in the diﬀerent bands for WLAN (IEEE 802.11 a/b/g/n), GSM (800 MHz, 850 MHz, and 1.9 GHz), Zigbee (IEEE 802.15.4), LTE, WiMAX (IEEE 802.16), etc. . Reconﬁgurability among such applications is desirable in IoT based communication, which can be achieved through frequency reconﬁgurable antennas. Many such antennas are proposed in the literature, and some of them are presented here. A new topology based multiband LP-RFID reader antenna is designed by Bashir et al. in , and a total UHF-RFID band of 840 MHz to 960 MHz, 2.4 GHz of ISM, and 5.77 GHz SHF band is covered by the antenna. In addition to that, it also covers TV bands (697 MHz to 884 MHz) and GSM band with a − 10 dB impedance matching. A frequency reconﬁgurable bow-tie antenna is designed for WiMAX, Bluetooth, and WLAN applications by T. Li in  in which the eﬀective length of the designed antenna is changed by employing p-i-n diodes on the bow-tie arms leading to tunable operating band. Sun et al. in  designed a compact reconﬁgurable patch antenna employed a shorting structure, which can switch among three bands. A reconﬁgurable circular disc antenna with a p-i-n diode switching able to switch between wideband state
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to this, the effect of cross-coupling between different microstrip patch antenna in multi-element array makes the situation further highly complex as well as challenging too. The terse review of literature revealed that the design of a two elements coaxial continuous transverse stub-array with omni- directional radiation pattern is reported  for C-band with improved performance in terms of efficiency as well as gain. The said antenna operates only at 5.18 GHz, 6.536 GHz and 7.42 GHz. Another reconfigurable micro-strip antenna is reported for 2.5GHz, 5.5GHz and 7.5GHz for Wi-Fi, Bluetooth, Wi-Max, satellite and maritime radar applications . However, the operation is not feasible at 10.7 GHz with these two available designs. The design of a flexible Yagi microstrip patch antenna is also detailed in the work at  which is designed using multilayer substrate having a size of 100×92.8mm for fixed-satellite, radiolocation, amateur- satellite service applications. It is again observed that the antenna has a multilayer complicated structure. The analysis of microstrip antenna array is done in the work at , which is embedded on composite laminate substrate. Many of the antenna array configurations including 1×2, 1×4, 1×8 linear array and, 2×2, 2×4 planar array are discussed to get better directivity. However, due to use of composite laminate substrate, the antenna design is a costlier affair as such composite laminate are not readily available. Thus, there is an urgent need to have antenna systems confirming to the requirements of conformal shape, aerodynamic profile, compact size, uncomplicated design, simple manufacturability, lighter and cost effective.
Abstract—In this paper, a novel quad-band combination of circularly-polarized microstrip antenna is proposed. This antenna has multi-frequency and quad-polarization with multiple coaxial probes, which cover four bands of the BeiDou navigation system (BDS), meeting diﬀerent application requirements. By using a stacked structure to achieve feed and using symmetrical slotted method to place the coaxial probes, the multi-frequency antenna is connected together through the middle co-aperture. Meanwhile, the feed position and size are constantly optimized until get the most suitable one, and the necessary perturbation is obtained. We also introduce a broadband stripline 90 ◦ bridge. Ultimately, the circularly-polarized and multi-frequency operation is achieved. Furthermore, the novel design enables easy implementation, miniaturization, wide band, which can meet the application requirements and promote the development of the BDS, which can be combined with the Internet of Things technology, applied to life and production.
The introduction mentions only a few of the commercial civilian uses of satellite navigation in everyday life. Since the installation of the GPS navigation system in vehicles in the early 1990s, its commercial uses have diversified. Systems with automated navigation, and the envisaged traffic management of the future, are commonly known as Intelligent Transportation Systems . The development and application of these systems in management, for example, has led to the establishment of a new branch of the economy called Precision management. The term Precision agriculture/Precision farming has become established in the field of agriculture, whereas in forestry the applications are developing at a slower rate due to poorer signal reception in forests. GPS users in forested and hilly areas should, along with the already mentioned components, have at their disposal an external antenna and an external source of power, which considerably increases the size of
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The AN/WSN-5 has the same output capabilities as the AN/WSN-2. It uses an accelerometer- controlled, three axis, gyro-stabilized platform to provide precise output of ship’s heading, roll, and pitch data in analog, dual-speed synchro format to support ship’s navigation and fire control systems. Ship’s heading and attitude data are continually and automatically derived while the equipment senses and processes physical and electrical inputs of sensed motion (inertial), gravity, earth’s rotation, and ship’s speed. The equipment has an uninterruptible backup power supply for use during power losses, and built- in test equipment (BITE) to provide fault isolation to the module/assembly level.
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