Low Cost GPS Receiver — A Satellite Navigation Receiver for the Global-Positioning-System

GPS for low-cost attitude determination: A review of concepts, in-flight experiences, and current developments

The “youngest” of the major satellite applications is the field of satellite navigation. This field of measurement and ranging through the use of satellite positioning systems first started in the context of scientific research. This initial use of satellites was simply for positioning and location. These activities, that were first based on using Doppler frequency shifts as a satellite orbited above, were largely scientific and not strategic. These types of activities included geodetics (i.e., such as the measurement of continental drift over time) or the collection of scientific information and data from atmospheric landor ocean-based sensors where the specific locations of the sensors were important. The real strides in the development of satellite navigation, however, came when space systems were developed for the specific purpose of precise targeting of missiles and various other types of weapon systems. The Soviet Union/Russian J.N. Pelton (*) International Space University, Arlington, VA, USA e-mail: joepelton@verizon.net S. Camacho-Lara Centro Regional de Ensenanza de Ciencia y Tecnologia del Espacio para America Latina y el Caribe (CRECTEALC), Santa Maria Tonantzintla, Puebla, Mexico e-mail: sergio.camacho@inaoep.mx # Springer Science+Business Media New York 2016 J.N. Pelton et al. (eds.), Handbook of Satellite Applications, DOI 10.1007/978-1-4614-6423-5_10-3 1 Federation satellite navigation system, known as GLONASS, and the US-based Navstar system –with its Global Positioning Satellite (GPS) network – developed space-based systems that provided unprecedented capabilities to determine locations on the ground or oceans with great accuracy. Early systems such as Argos that relied on Doppler shift technology were only accurate within a precision of hundreds of meters. Today’s advanced satellite navigation systems, however, are accurate for measurements that can be indicated with a precision only a few meters and within centimeters if utilizing reference stations. The fact that GPS and GLONASS satellite signals are freely available in space for all to use has spurred the development of low-cost receivers for much more than strategic or military usage. Today, various types of civilian use of navigational and positioning satellites have become popular on a global basis. The latest development in application-specific integrated circuit (ASIC) chip technology has fueled the growth of applications based on the use of these precise spacebased navigational and positioning systems. The availability of these highly capable but increasingly low-cost chips – small enough that they could be included in handsets such as cell phones or included with the electronics available on various types of vehicles (i.e., cars, trucks, buses, trains, airplanes, ships, etc.) – represented a real breakthrough. The development of specialized computer chips to perform satellite navigation calculations has increased the number of users of this technology from a relatively small population of several thousands to tens of millions. In the coming decade, the proliferation of international satellite navigation systems in orbit (i.e., USA, Russian Federation, China, India, Europe, and Japan) plus the continued development of ever lower cost of satellite navigation chips for receivers will continue the popular expansion of these increasingly “easy to use” and versatile systems. Wide and easy access to low-cost consumer receivers for satellite navigation services strongly suggests that this trend of expanded use will continue to surge. Thus, within a decade, use of these devices will increase to the hundreds of millions if not billions of people. Atomic clocks with incredible temporal precision today allow satellite navigation systems to be used by military organizations, governmental geospatial scientists, and scientists to determine locations with great accuracy. But these applications are now just a small fraction of total usage. The deployment of the new international satellite navigational systems and smaller and lower cost ground receivers will support an ever-increasing civilian consumer market for an ever-expanding range of everyday applications. These consumer applications include driving a vehicle to a desired location, safely sailing a boat, going mountain climbing or hiking without getting lost, or simply finding out where you are within a city. The precise time keeping ability of today’s satellite navigation systems also means that these spacecrafts can also serve as a global timekeeper for computers and scientific experiments. The time stamp from a satellite navigation satellite can also be used not only for scientific or regulatory purposes but for other applications such as security and banking systems as well. These satellites are also used to support the synchronization needs of communications satellites. In short, 2 J.N. Pelton and S. Camacho-Lara

A novel framework is proposed and demonstrated where satellite visibility viewed from running vehicle is economically and effectively evaluated with such low cost GPS receivers like equipped in automobiles. Our preliminary experiment articulated even economical Ll C/A 1.5GHz GPS receivers can create enough precise database of ground feature blockage, if only two statistical parameters the author proposed are adequately set. Integrating the series of our efforts on this research field, the author also concluded it is feasible to develop an automatic database creation system by the cooperation of the government and the civil with low cost GPS receivers. This blockage database allows us to make feasible real-time handover for running emergency or rescue vehicles in near future’s Land Vehicle Satellite Communication Society.

Knowledge of the state of the upper atmosphere, and in particular its ionospheric part, is very important in several applications affected by space weather, especially the communications and navigation systems that rely on radio transmission. To better classify the ionosphere and forecast its disturbances over Europe, a data collection endeavour called the European Digital Upper Atmosphere Server (DIAS) was initiated in 2004 by a consortium formed around several European ionospheric stations that transmit in real-time ionospheric parameters automatically scaled. The DIAS project is a collaborative venture of eight institutions funded by the European Commission eContent Programme. The project seeks to improve access to digital information collected by public European institutes and to expand its use. The main objective of the DIAS project is to develop a pan-European digital data collection describing the state of the upper atmosphere, based on real-time information and historical data collections provided by most of the operating ionospheric stations in Europe. Various groups of users require data specifying upper atmospheric conditions over Europe for nowcasting and forecasting purposes. The DIAS system is designed to distribute such information. The successful operation of DIAS is based on the effective use of observational data in operational applications through the development of new added-value ionospheric products and services that best fit the needs of the market. DIAS is a unique European system, and its continuous operation will efficiently support radio propagation services with the most reliable information. DIAS began providing services to users in August 2006. The Need for Accurate Ionospheric Products Radio frequency communications and satellite positioning and navigation systems are applications most affected by ionospheric disturbances. Such disturbances can cause drastic and large-scale changes in the usable ranges of high frequency (HF) or below HF bands affecting standard ground-to-ground and submarine communication systems. The characteristics of an ionospheric propagation channel, whether it is HF or transionospheric frequencies, are highly variable on timescales ranging from a few seconds to the 11-year solar cycle. Even during its quietest periods, the Sun produces electromagnetic radiation and solar wind, both of which can affect a variety of geomagnetic and ionospheric phenomena, which in turn affect radio waves propagating through the ionosphere. Hence day-to-day and hour-to-hour changes in propagation channel characteristics can occur.

Within the PROBA-2 microsatellite mission, a miniaturized single-frequency GPS receiver based on commercial-off-the-shelf (COTS) technology is employed for onboard navigation and timing. A rapid electronic fuse protects against destructive single-event latch-ups (SEL) and enables a quasi-continuous receiver operation despite the inherent sensitivity to space radiation. While limited to single-frequency C/A-code tracking with a narrow-band frontend, the receiver is able to provide precision navigation services through processing of raw GPS measurements on ground as well as a built-in real-time navigation system. In both cases, ionospheric path delays are eliminated through a combination of L1 pseudorange and carrier phase measurements, which also offers a factor-of-two noise reduction relative to code-only processing. By comparison with satellite laser ranging (SLR) measurements, a 0.3-m (3D rms) accuracy is demonstrated for the PROBA-2 reduced dynamic orbit determinations using post-processed GPS orbit and clock products. Furthermore, the experimental onboard navigation system is shown to provide real-time position information with a 3D rms accuracy of about 1 m, which notably outperforms the specification of the Standard Positioning Service (SPS). In view of their lower hardware complexity, mass budget and power requirements as well as the reduced interference susceptibility, legacy C/A-code receivers can thus provide an attractive alternative to dual-frequency receivers even for demanding navigation applications in low Earth orbit.

In this paper we study the contribution of inter-vehicular communication in ADAS applications. We thus propose a collaborative system on the crossroads using our 802.11g communications tools and a low cost GPS receiver. Once the vehicles positions exchanged, the crash avoidance is performed by predicting the future positions of both cars and calculating the time to impact and the region of high risk. The prediction is biased in time and space. The time error is due to the GPS and the communication latencies. We thus propose an estimation of both latencies and integrate them in the prediction loop. The space error is caused by the uncertainty of the positions delivered by the GPS receivers. We compensate this error not by considering a deterministic position of the vehicle but by a probability of being in a region of space and by proposing a Kalman filter which first reduces noise on the positioning and second estimates the variance of error on the measurement. This approach is validated through real scenarios of road crossing. We show thus the contribution of the cooperation via the communication devices in the reduction of accidents rate on the crossroads

Agriculture sector is growing rapidly in the modern era due to rise in global population and shift in trade policies. Replacing human labor with automation of agricultural equipment can alleviate labor shortages and rising costs of farm work to a greater extend. With the inclusion of GPS for navigation, IoT connectivity for remote monitoring and operation, cameras and machine vision systems, the autonomous vehicles will become more capable and self-sufficient over time. However, automation costs need to be reduced to gain a broader acceptance. Tracking a vehicle with low-precision GPS receivers tends to have errors, whereas the inclusion of a high-precision GPS receiver raises the overall cost of the vehicle. In this work, a machine learning-based post-processing techniques have been proposed to enhance position accuracy of a low-cost GPS receiver implemented on an autonomous harvester for monitoring and navigation purpose. The proposed system is integrated with cloud technology where the location coordinates from low-cost GPS receiver get updated to ThingSpeak cloud server using microcontroller. The user can track the position of the vehicle on a smart phone using the designed android app and configure the Geofence around the field for the harvester vehicle to work on. The Geofence alerts the user once the harvester vehicle moves out of the designated field.

Satellite navigation system plays an important role in people's daily life and war. The strategic position of satellite navigation system is prominent, so it is very important to ensure that the satellite navigation system is not disturbed or destroyed. It is a critical means to detect the jamming signal to avoid the accident in a navigation system. At present, the detection technology of jamming signal in satellite navigation system is not intelligent , mainly relying on artificial decision and experience. For this issue, the paper proposes a method based on deep learning to monitor the interference source in a satellite navigation. By training the interference signal data, and extracting the features of the interference signal, the detection sys tem model is constructed. The simulation results show that, the detection accuracy of our detection system can reach nearly 70%. The method in our paper provides a new idea for the research on intelligent detection of interference and deception signal in a satellite navigation system.

Navigation signals are the basis of satellite navigation systems, which determine the navigation systems' performance (such as tracking accuracy, anti-interference capability etc.), and are determined by some constraints (such as radio frequency resources, construction cost, technology level etc.). The aim of signal design is to select "proper" signals considering these above factors and make tradeoffs between performance and constraints. This paper will summarize the signal structure evolution of present satellite navigation and conclude some principles and issues which will be greatly valuable to our 2nd satellite navigation system. There's four main satellite positioning systems presently, the U.S. Global Positioning System (GPS), the Russian Global Navigation Satellite System (GLONASS), the Europe Galileo satellite navigation system and the Chinese BD-1 satellite positioning system. Among these systems, the signal characteristics of GPS and Galileo are good reference to our 2nd satellite navigation system. The improvement of GPS signals is a main aspect of GPS modernization. The aim of GPS modernization is mainly to modernize its signal structure so as to improve the whole systems' performance. The signal structure of Galileo has been revised for several times, and its present signal is the results of long time signal design. From GPS modernization and Galileo signals status, we can summarize some key specifications of navigation signals and some technologies to support these specifications. Based on this, we'll discuss some problems which should be attentive in our country's 2nd satellite navigation system and give some suggestions. This paper is organized into five sections. The first section will give a brief introduction of present satellite navigation system and their main features. Section two will review the GPS and Galileo signals structure evolution, including GPS modernization, Galileo signals status and the comparison of two systems' signals. In the third section, the relationship between signal parameters and system performance will be analyzed, including RF signal characteristics, modulation type, ranging code (such as code type, length and rate) and navigation data. In section four we will discuss some inspiration and technologies concerning our 2nd satellite navigation system, such as the use of multiple frequency signals (ionospheric delay estimation and carrier ambiguity resolution), pilot tones & dataless channel, binary offset carrier (BOC) modulation, and so on. The last section is conclusion, in which the whole paper will be retrospected and some useful conclusion will be given.

In this paper, an integrated navigation system based on MEMS-IMU/GPS is implemented through optimization of GPS information processing and Kalman filter algorithm. Low-cost IMU and GPS receivers are used with STEM32 as the core of information processing. An improved speed/position combination is adopted in this paper. Test results are presented showing the performance of the integrated MEMS GPS/inertial navigation system: This measure improves aircraft navigation accuracy and corrects the divergence more quickly. This allows integration with less errors characteristic, which is more suitable for aircrafts with low-cost, low-power, lightweight GPS chip receivers and navigation sensors.

Position determination using satellite navigation system has grown significantly. It provides geospatial with global coverage called GNSS (Global Navigation System Satellite). GNSS satellites consists of GLONASS, GPS (Global positioning system) and Galileo.GPS is the most commonly used system and it is known to its capability to determine 3D position on the surface of the earth. In order to determine the position, a GPS receiver must be able to receive signals from at least four GPS satellites. However, the determination of position in condensed areas such as tunnels, area surrounded by high rise buildings, highly forested and in other closely-knit areas is not achieved because satellite signals cannot reach the receiver in the above-mentioned areas and also others where the signals are reflected before being received by a GPS receiver. In this paper, we present the algorithm to fuse GPS and the inertial measurement unit (IMU) to enable positioning in the above-mentioned Condensed Areas. The standard deviations of the two measurements show that GPS-IMU is better than GPS alone, the standard deviation when satellite outages occurred is - 4.57475 for GPS-IMU measurements and 0.218675 for GPS observations. We presented the results in graphics and it shows that GPS measurements are easily disturbed by external influence such as multipath but GPS-IMU graphic is continuous and robust. The advantages and disadvantages of GPS and INS are complementary and make them work together to enable the accurate measurements in the areas mentioned above. Integration of INS and GNSS can be classified into three types, loosely coupled Kalman filter, tightly coupled Kalman filters and ultratight coupled Kalman filter. In this research we used loosely coupled Kalman filter and tightly coupled Kalman filters to combine GPS and INS in one system.

The performance of low-cost RTK (real-time kinematic) GPS receivers has been compared to a state-of-the-art system as well to each other. Both static and dynamic performances have been compared. The dynamic performance has been evaluated using a vehicle with driving robot on the AstaZero proving ground. The assembly of the low-cost RTK GPS receivers is presented, and the test set-ups described. Besides having a lower data output frequency, two of the low-cost receivers have static and dynamic performance not far from that of the state-of-the-art system.

Methods of the actual values of the angles of attack and slip determination in the technology of air data systems estimation using satellite navigation systems during aircraft flight tests of are stated. Also methods of parametric identification of mathematical models of on-board aerodynamic angles measurements errors are presented. The technology has been developed and implemented in the practice of flight tests at Flight Research Institute. The technology shows high efficiency of solving tasks of air data on-board systems, vertical separation systems, flight performance and takeoff and landing characteristics estimation in flight tests. The technology covers a wide range of issues of aerometric measurements, many of which have already been published. Here, attention is paid to measurements of aerodynamic angles. The features of determining the angles of attack and slip using data from air data systems, satellite and inertial navigation systems are shown. Equations for determining the angles of attack and slip during testing, factors of measurement errors, the structure of the mathematical model of the aerodynamic errors of the angle of attack on-board measurements are presented in a stationary approximation. Algorithms for solving problems in steady and unsteady modes of flight, takeoff and landing are considered. The completeness of the solution for the wind speed vector is noted. Estimates of methodological errors in determining aerodynamic angles using the technology are made. Compliance with modern requirements is showing. The effectiveness of the technology is confirmed by the materials of flight tests of a short-range aircraft. Typical examples of test materials presentation, features of measurements depending on the type of test mode, aerodynamic influence factors are shown.

Deliberate jamming of Global Navigation Satellite Systems (GNSS) is becoming more and more a problem in both Navigation Warfare and civilian use of the system. For a better understanding of the effects of a jammer on a GPS receiver we conducted an experiment including a low-cost GPS receiver. This paper discusses the results of this experimental study in which we investigated the influence of radio frequency interference on positioning using a low-cost GPS receiver. The study has been performed with an experimental set-up where a jammer influences a software defined receiver at several distances in an open field. Post-processing the measurements showed that for certain distances the receiver was unable to receive the signals of some satellites with the jammer active. As a result the 95% confidence ellipses enlarged in these situations. Furthermore it was observed that size of the confidence regions depend heavily on the geometry of the satellites, whose signals could be received in the measurements. Results on the pseudorange errors for several jammer to receiver distances are also included in the paper.

In industrial applications is a demand for the highly reliable and synchronous distributed systems. The problem is that in those systems the nodes maintain their own time using local clocks. This behavior can be suppressed by synchronization of the individual nodes. It is more effective to use GPS for synchronization in large distributed systems. This paper deals with evaluation of reachable accuracy of synchronization within industrial distributed system using low-cost GPS receivers. Results of measurements using the uBlox LEA-6T GPS Receiver confirm achievable accuracy better than 15 ns in terms of an RMS value.