gps and glonass constellations

gps and glonass constellations插图

The Global Positioning SystemGlobal Positioning SystemThe Global Positioning System (GPS) is a space-based navigation system that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. The system provides critical capabiliti…en.wikipedia.org(GPS) GPSis a GNSSAssisted GPSAssisted GPS (abbreviated generally as A-GPS and less commonly as aGPS) is a system that often significantly improves startup performance—i.e., time-to-first-fix (TTFF), of a GPS satellite-based positioning system.en.wikipedia.orgconstellation, but GNSS is not always GPS. GPSis one of the 5 GNSS constellationsused around the world. The 5 GNSS constellationsinclude GPS (US), QZSS (Japan), BEIDOU (China), GALILEO (EU), and GLONASSGLONASSGLONASS, or GLObal NAvigation Satellite System, is a space-based satellite navigation system operating in the radionavigation-satellite service and used by the Russian Aerospace Defence Forces. It provides an alternative to GPS and is the second alternative navigational system in operati…en.wikipedia.org(Russia).

What is the difference between GPS and GLONASS constellations?

Differences between GPS and GLONASS constellations are summarized in the following table: GLONASS GPS GALILEO Number of nominal satellites 24 24 30 Number of orbital planes 3 6 3 Orbital Inclination 648′ 55 56 Orbital altitude 19.140 km 20.180 km 23.222 km 5 more rows …

What are the 5 GNSS constellations?

The 5 GNSS constellations include GPS (US), QZSS (Japan), BEIDOU (China), GALILEO (EU), and GLONASS (Russia). We’ll cover each of these constellations in-depth in this post. The main reason for all 5 satellite constellations is availability and redundancy. If one system fails, another GNSS constellation can help take over.

Are the frequencies different between GLONASS satellites?

The frequencies are different between GLONASS satellites. IGS has established the MGEX to serve as a platform for investigating the emerging new navigation systems such as BeiDou and Galileo ( Rizos et al., 2013 ).

What are the different versions of GLONASS?

Versions- The various versions of GLONASS are GLONASS – launched in 1982, the satellites launched were intended to work for weather positioning, velocity measuring and timing anywhere in the world or near-Earth space by the military and official organisations. GLONASS-M – launched in 2003 add second civil code.

How many satellites are in the GLONASS system?

The fully operational system consists of 24+ satellites.

What is BDS in China?

BeiDou, or BDS, is a global GNSS owned and operated by the People’s Republic of China. BDS was formally commissioned in 2020. The operational system consists of 35 satellites. BDS was previously called Compass.

How many satellites are there in IRNSS?

IRNSS is an autonomous system designed to cover the Indian region and 1500 km around the Indian mainland. The system consists of 7 satellites and should be declared operational in 2018. In 2016, India renamed IRNSS as the Navigation Indian Constellation (NavIC, meaning "sailor" or "navigator"). Learn more:

What is a GNSS?

Navigation Signals. Global navigation satellite system (GNSS) is a general term describing any satellite constellation that provides positioning, navigation, and timing (PNT) services on a global or regional basis. While GPS is the most prevalent GNSS, other nations are fielding, or have fielded, …

Who owns QZSS?

Quasi-Zenith Satellite System (QZSS) QZSS is a regional GNSS owned by the Government of Japan and operated by QZS System Service Inc. (QSS). QZSS complements GPS to improve coverage in East Asia and Oceania.

Is GPS a GNSS?

While GPS is the most prevalent GNSS, other nations are field ing, or have fielded, their own systems to provide complementary, independent PNT capability. The main ones are described below. GNSS can also refer to augmentation systems, but there are too many international augmentations to list here. Some links below lead to external websites …

Who owns Galileo?

Galileo is a global GNSS owned and operated by the European Union. The EU declared the start of Galileo Initial Services in 2016 and plans to complete the system of 24+ satellites by 2020.

What was the purpose of the prototype board?

A prototype board was developed to compare the performance of both solutions, single and multi-GNSS time reference based clocks.

What is satellite data?

This technique consists of using satellite data from different navigation systems and combining them as if it was a single system providing one time reference. Such a solution, besides not being expensive or difficult to implement, offers great advantages over using

How many satellites are in orbit?

Conceived for military purposes in 1973 by the United States, the system was declared totally operational in 1995. Today it counts with 31 satellites that were launched to orbit for years, starting in 1978. Despite of the total, only 24 satellites are available simultaneously; the other ones are operational only in case of a failure or for data checks. The satellites orbit Earth at 20200 kilometers up in the sky and complete two full turns around the globe per day. They have a longitudinal trajectory with different angles for each satellite.

What is the demand for accurate time synchronization?

The demand for accurate time synchronization available 24/7 increases with the growth of critical substation applications, such as phasor measurement, merging units , traveling-wave fault location and current differential protection schemes . In order to yield the best accuracy and granularity from such applications, the use of a common, reliable and precision-time reference is essential.

When was the Russian navigation system developed?

The Russian navigation system GLONASS started to be developed in 1976 also for military purposes. The project was interrupted for many years after the end of the Soviet Union but it was reestablished and gained notoriety during the last decade, driven by the Russian president Vladmir Putin.

Is a single GNSS time reference?

Using a single GNSS as a time reference is the most used solution, commonly relying on the GPS, but using a single solution introduces some vulnerabilities and limitations to the system

What does GPS stand for?

GLONASS is Russia’s version of GPS (Global Positioning System).

How many satellites are there in GPS?

GPS developed by USA has a network of 31 satellites covering this planet and has been widely used in commercial devices like mobile phones, navigators etc. GLONASS is developed by Russia originally started by Soviet Union in 1976. This has a network of 24 satellites covering the earth. The image shows the orbit and constellation of GLONASS (left) …

How many satellites are in the Indian Regional Navigation Satellite System?

This system would consist constellation of 7 satellites out of which 4 are already placed in the orbit. The project is expected to be operational by 2016.

What devices support GPS?

All the high end devices that supports GPS facilities, especially navigators include GLONASS receivers on their chip to use location based services.

What does A-GLONASS do?

A-GLONASS also enhances the performance in chip-sets that come with GLONASS support.

When was the first GLONASS launched?

Versions-. The various versions of GLONASS are. GLONASS – launched in 1982 , the satellites launched were intended to work for weather positioning, velocity measuring and timing anywhere in the world or near-Earth space by the military and official organisations. GLONASS-M – launched in 2003 add second civil code.

Does iPhone 4S have GPS?

iPhone 4S was the first apple product to use both GPS and GLONASS for pinpointing location on maps. All the high end devices that supports GPS facilities, especially navigators include GLONASS receivers on their chip to use location based services.

What Do All GNSS Constellations Have In Common?

The short answer is the need for accurate timing and accuracy. This is typically achieved by high-performance rubidium atomic clocks or LEO Satellite GPSDOs. Here at Bliley Technologies, we’ve applied over 85 years of frequency control experience to bring the world some of the best timing solutions for GNSS constellations and LEO satellites.

How accurate is GPS?

Today, GPS is the most accurate navigation system in the world. The latest generation of GPS satellites use rubidium clocks that are accurate up to ±5 parts in 1011. These clocks are synchronized by even more accurate ground-based cesium clocks.

What is Galileo compatible with?

GALILEO is Europe’s GNSS system that’s compatible with GPS and GLONASS. It started providing service in December 2016.

What is the oldest GNSS system?

1. GPS. GPS is the pioneer in the world of GNSS. It’s the oldest GNSS system that began operation in 1978 and was made available for global use in 1994. GPS was invented from the need for an independent military navigation system. The United States Department of Defense (DoD) was the first to realize this.

How many satellites does QZSS use?

QZSS currently uses one geostationary satellite orbit and three in the QZO orbit ( highly inclined, slightly elliptical, geosynchronous orbit).

Why are there 5 satellite constellations?

The main reason for all 5 satellite constellations is availability and redundancy. If one system fails, another GNSS constellation can help take over. System failures don’t happen often, but it’s comforting to know there are backup options.

What frequency band is GPS?

GPS operates in a frequency band referred to as the L-Band, a portion of the radio spectrum between 1 and 2 GHz. L-Band was chosen for several reasons, including: 1 Ionospheric delay is more significant at lower frequencies 2 Simplification of antenna design 3 Minimize the effect that weather has on GPS signal propagation

Cobus Heukelman in Blogs on October 16, 2015

In the last few years many chipsets have become available that have the ability track satellite constellations in addition to GPS. The question that we often get from customers is: Which is best for my application, GPS or GLONASS? The quick answer is: "Use both of them." Unfortunately, the more constellations you add, the higher the price.

A Quick Review of Satellite Technology

Let’s take a step back and look at the technology as a whole. A group of satellites that provide location info is called a constellation. The satellites broadcast signals to Earth, and by calculating the difference in timing of the received signals from various satellites, a receiver can figure out where it is located.

The Differences Between GPS and GLONASS

Now that we have an idea of how the system works and what we need for tracking, let’s compare GPS with the Russian GLONASS system. For GPS, the US has committed to maintaining at least 24 operational GPS satellites, 95% of the time. In the past few years 31 satellites have been steadily operational.

Available GPS Modules

So if your product will always have an unobstructed view of the sky, or you would like the cheapest solution, then I would recommend GPS. Telit has many GPS modules with excellent performance to offer. Their smallest GPS module, the SE880, is only 4.7 x 4.7mm, excluding the antenna.

How many satellites are in the GLONASS space segment?

The GLONASS space segment consists nominally of 24 operational satellites, distributed over three orbital planes. The longitude of ascending node differs by 120 deg from plane to plane. There are eight satellites per plane, separated 45 deg in argument of latitude. The difference in the argument of latitude of satellites in equivalent slots in two different orbital planes is 15 deg. Each satellite is identified by its slot number, which defines the orbital plane and its location within the plane.

How long does it take for a GPS satellite to complete its orbit?

GLONASS satellites operate in circular orbits at an altitude of 19100-km, an inclination of 64.8 deg and each satellite completes the orbit in approximately 11 hours 15 minutes. This means that for a stationary observer the same satellite is visible at the same point in the sky every eight sidereal days. Since there are eight satellites in each orbital plane, satellite positions in the sky get repeated each (although by different satellites). With the 11 h 58 min orbital period for GPS satellites, the same GPS satellite is visible at the same point in the sky every (sidereal) day.

What is the function of the GLONASS space segment?

GLONASS Space Segment. The main functions of the Space Segment are to transmit radio-navigation signals, and to store and retransmit the navigation message sent by the Control Segment. These transmissions are controlled by highly stable atomic clocks on board the satellites. The space segment is defined by the number of satellites in …

How long does a GLONASS satellite last?

GLONASS-M satellites have a longer design lifetime of seven years as a result of propulsion system and clock stability (Cesium clocks) improvements. This is a big lifetime increase compared with the 2-3 years of previous first generation spacecraft, but it is still under the 10 years mean life of the GPS.

When were the first GLONASS satellites launched?

Prototypes (Generation zero) .The first prototypes of GLONASS (Uragan) satellites were sent into orbit in October 1982, being up to 18 spacecrafts launched between 1982 and 1985.These first GLONASS satellites are referred to as Block I vehicles and, although being designed to last only one year, many of them had an actual lifetime up to more than 14 months.

What do satellites carry?

Satellites carry atomic clocks and the payload needed for handling (recei ving, processing and transmitting) navigation data. They also have reflectors to allow laser ranging from dedicated ground stations.

What does a GLONASS M mean?

Second generation, GLONASS-M (or Uragan-M) is the second generation of satellites, where -M indicates modernized or modified.

How does a GNSS receiver work?

GNSS receivers use a lower accuracy clock that is then disciplined to GPS time using the specific timing messages in the signals sent from the satellites to the receivers. Once in sync with GPS time, the receiver can output a pulse per second signal, or PPS, on the top of every second in GPS time.

How long does it take for a satellite to update its ephemeris?

Therefore, the ephemeris is updated for each of the satellites every four hours by the Ground Control Segment. Fortunately, downloading the full ephemeris from a satellite only takes a GPS receiver approximately thirty seconds.

What is a GNSS satellite?

1.2 Global Navigation Satellite System (GNSS) A Global Navigation Satellite System (GNSS) is a satellite configuration, or constellation, that provides coded satellite signals which are processed by a GNSS receiver to calculate position, velocity, and time. GNSS is a passive system, meaning that there is no limit to the number …

Why does a GNSS receiver shift?

As a GNSS receiver is receiving and tracking a signal from a satellite, the frequency of the signal appears to shift due to the combined motion of the user and of the satellite orbiting around the Earth. This shift in frequency can be used to determine a relative speed.

What is the navigation message?

Navigation Message. The signals that the Ground Control Segment sends to the satellites which then get sent to the end user are known as the navigation message. The GPS navigation message contains four main parts: GPS time, satellite health, ephemeris, and the almanac.

Why do GPS receivers use low end clocks?

Receivers use low-end clocks for timing , not atomic clocks, resulting in an unknown bias from the true GPS time. Due to this clock bias error, receivers are not measuring the true range to the satellite, but rather a pseudorange ( ρ ). The pseudorange is the basis for calculating a user’s position and time.

What are the segments of GNSS?

GNSS operates through three different segments known as the Space Segment , the Ground Control Segment , and the User Segment, as shown in Figure 1.3a. The Space Segment consists of the satellites themselves placed into a specific constellation, as seen in Figure 1.3b. The Ground Control Segment utilizes Earth based tracking stations around the world to manage the entire navigation system. Specific locations of these stations for the U.S. based system, GPS, are shown in Figure 1.4. The User Segment is comprised of the GNSS receivers that can be used anywhere around the world.

Abstract

Multi-constellation GNSS precise point positioning (PPP) first became feasible back to 2007 but with only two constellations, namely GPS and GLONASS.

1. Introduction

GPS-based precise point positioning (PPP) is widely used for scientific research and industrial applications. However, it requires a significant time for the position solutions to converge. Many efforts have been made to improve the PPP performance, such as improving the quality of precise satellite orbit and clock products (e.g.

2. PPP model with quad constellations

The pseudorange and carrier-phase observations on i th ( i = 1, 2) frequency can be expressed as: (1) P i j = ρ j + cdt – cdT j + d orb j + d trop j + d ion / L i j + b P i j + ε P i j (2) Φ i j = ρ j + cdt – cdT j + d orb j + d trop j – d ion / L i j + B i j + ε Φ i j where the superscript j represents a GNSS satellite, Pi is the measured pseudorange on i th frequency in meters, Φi is the measured carrier phase on i th frequency in meters, ρ is the geometric range in meters, c is the speed of light in meters per second, dt is the receiver clock offset in seconds, dT is the satellite clock offset in seconds, dorb is the satellite orbit error that is projected onto the line of sight from the receiver to the satellite in meters, dtrop is the tropospheric delay in meters, dion/Li is the ionospheric delay on i th frequency in meters, Bi is the phase ambiguity term on i th frequency in meters, which includes the receiver and satellite initial phase biases and phase hardware delay biases, bPi is the hardware delay bias in the code observations on i th frequency in meters, ?Pi and ?Φi are the code and phase observation noises including multipath in meters, respectively..

3. Performance analysis of positioning solutions with quad-constellations

The datasets collected at five stations on sixteen consecutive days, i.e. March 8–23, 2014, are used for numerical analysis. The station location, receiver and antenna information are listed in Table 1. All stations were equipped with multi-GNSS receivers which can produce the observations from GPS, BeiDou, GLONASS and Galileo constellations.

4. Analysis of system time difference solutions between constellations

In order to analyze its temporal variation characteristics, the system time difference estimates (STDE) are obtained at five stations from daily PPP solutions rather than three-hour solutions to avoid frequent convergence process. The same datasets and processing settings are used as those in Section 3.3. Fig.

5. Conclusions

BeiDou and Galileo have begun to transmit real signals for position determination. The recent availability of their precise products enables precise point positioning (PPP) with quad-constellations. In this study, the quad-constellation PPP model is developed to simultaneously process the observations from all four GNSS systems.

Acknowledgments

The financial supports from Scientific Research Fund of Hunan Provincial Education Department (No. 13K007 ), Teacher Research Fund at Central South University (No. 2013JSJJ004) and China Postdoctoral Science Foundation (No. 2014M550425) are greatly appreciated. Contribution of data from IGS, GFZ, ESOC and IAC is also appreciated.