The month of October and now into November was filled with several conferences, but not a lot of location news. A few news snippets, while not blockbusters, were important. One was Waze’s decision to offer its own location-based advertising. Another was a milestone for Ford, which said its Sync information system is now in five million vehicles. On an end-of-an-era note, of which there have been quite a few in the last two years, Sprint has decided to drop the Nextel name. Nextel was one of the innovative companies in the late 1990s and early 2000s, placing location capability into mobile phones and jump-starting an industry.
Waze recently said it is offering a global location-based advertising platform that will be directed to its 30 million users. Waze, founded in 2009 in Israel, says smartphone users can try the service for free — the profit for them is ad revenue from local and large brands.
GPS World’s LBS Insider recently reported that Tim Cook, Apple’s chief executive, actually endorsed Waze as an alternative to its own mapping service after users were experiencing problems with it. Waze, which is offering the advertisements in the United States, said it saw a jump in downloads after the announcement.
Some industry analysts say it may be a mistake for Waze to swim in the deep end of the pool to compete with such mobile advertising giants as Google.
Waze raised a total of $67 million from investor Kleiner Perkins and Hong Kong investor Li Ka-shing. They cite big partners such as Circle K, Dunkin’ Donuts, MACS, Kum & Go, Wyndham Hotels, Jamba Juice, and P&G.
Palo Alto-based Waze is probably best known for its driving directions based on user input. The company says that its users spend an average of more than 7 hours in their vehicles a month.
The company, in order not to annoy users, is minimizing the number of pins on a map advertisement. According to published reports, the company said its advertisements will include coupons.
From the Waze blog: “We don’t want to bombard you, so you’ll never see too many businesses crowded on the map at once. Instead, the algorithm that powers Waze Ads aims to bring you a helpful selection of the various retailers around you on your daily drive.”
Waze is also making advertising inroads in Europe. It recently announced a partnership with Lumata, an Italy-based mobile marketing company. The deal allows Lumata to have a an exclusive right for advertising on Waze’s app in Italy, according to published reports.
Waze announced in June that car models will soon integrate the company’s mapping software. The company’s iOS and Android app’s users contribute road data while they drive, share accident reports, police speed traps, traffic jams and other data.
Five Million Sync Units in Five Years…
Ford and Microsoft’s Sync infotainment system has been installed in five million Ford and Lincoln vehicles. The unit, which was rolled out at the 2007 Consumer Electronics Show in Las Vegas, was one of the first products to allow smartphones to work with car components.
Sync was innovative in that it bundled turn-by-turn navigation, hands-free calling, text message reading, and other features. Earlier aftermarket products, such as Clarion’s AutoPC, were busts — but perhaps five-to-seven years too early for the market.
Ford jazzed up Sync with touchscreens and voice recognition since it rolled out its first model, which only used push buttons. It integrated other features such as audio, air conditioning/climate control, and navigation. Soon the newer version, MyFord Touch, offered video streaming, music, and a voice-activated climate control system.
Ford announced earlier this year that it was working with State Farm to add all Sync-equipped vehicles to the insurance giant’s Drive Safe & Save approved vehicles. A customer, through a voluntary sign up, can run a Vehicle Health Report that sends information to State Farm. Potential insurance savings for a customer could be 40 percent.
Ford is working with several industry companies, including Pandora and TeleNav Scout, through its AppLink program, which was globally offered earlier this year.
In other LBS news:
Sprint’s recent decision to drop the Nextel name was the end of an era, but not a surprise. It was Nextel, before its 2005 merger with Sprint, that truly innovated consumer and enterprise applications and markets on the mobile handset. In the wake of Japan’s Softbank purchase of 70 percent of Sprint, the Nextel part of the Sprint name will go away in mid-2013. The new name will be Sprint Corp. The Nextel brand was known for its iDEN technology and network, which is gradually being shut down by Sprint.
The recent U.S. presidential election had an LBS story. Foursquare had an app that had the goal of encouraging users to vote. The “I Voted” app allowed users to find their local polling station on Election Day and check in to show they cast a vote. Foursquare, trying to show that it offers more than “check-in” capability, recently announced a rating system for businesses. It is not clear whether the service, with 25 million users, is going after companies such as TripAdvisor and Yelp for a share of the evaluation/services market.
Samsung Electronics’ Galaxy S III managed to knock Apple’s iPhone 4S off the pedestal as the world’s most popular smartphone, in terms of sales, in the third quarter, said Strategy Analytics. Samsung sold around 18 million S III phones during the quarter, compared to Apple’s 16.2 million iPhone 4S units. The Galaxy S features a large touchscreen and GPS for location-based services.
General Designer of Russia’s GLONASS satellite navigation system Yuri Urlichich has been dismissed from his post in the wake of an embezzlement scandal, a spokesperson for RF Deputy Prime Minister Dmitry Rogozin, who is in charge of the military-industrial complex, told Itar-Tass.
Urlichich still holds the position of Director General of Russian Space Systems (RSS), but is no longer the chief designer of Russia’s GLONASS system.
The personnel decision is apparently related to a scandal involving embezzlement of 6.5 billion rubles ($200 million) of the GLONASS programs funds at RSS, Deputy Prime Minister Dmitry Rogozin told the RIA Novosti news service on Sunday. Rogozin heads the government’s military-industrial commission.
According to Igor Bozhkov, head of the Moscow Metro Internal Affairs Department, RSS’ initial contract with Russian space agency Roscosmos allowed the company several avenues for embezzlement.
No charges were reported against Urlichich or other GLONASS makers as of late Sunday.
The Washington Post is reporting that President Vladimir Putin’s chief of staff was aware of alleged embezzlement of state funds earmarked for GLONASS. Sergei Ivanov said he discussed the probe with police officials but didn’t speak publicly about it for several years, to prevent the culprits from covering up their deeds. Ivanov, a KGB veteran like Putin, said years in the spy service taught him to be sly with the enemy. As a former cabinet member, Ivanov previously oversaw the development of the GLONASS system.
A new report from Juniper Research has found that with brands and retailers increasingly keen to deploy augmented reality (AR) capabilities within their apps and marketing materials, AR applications will generate close to $300 million in revenues globally in 2013.
The report found that while the traditional pay-per-download payment model would continue to account for the largest share of revenues in the medium term, the scale of retailer engagement with AR suggested that ad spend had upscaled dramatically in 2012 and was poised for further strong growth next year.
Crucially, it also found that many retailers now perceived AR as a key means of increasing engagement with consumers, both as a means of providing additional product information or in the form of branded virtual games and activities.
Consumer Expectations Not Yet Met. The report cautioned that while lack of consumer awareness of AR remained a key hurdle which needed to be overcome, it was by no means the only barrier to growth. It argued that technological limitations of AR-enablers such as the phone camera, GPS, digital compasses and marker-less tracking meant that in many cases, the AR experience was failing to live up to consumer expectations.
The report claimed that even some higher-end smartphone cameras lacked sufficient sensitivity to trigger an AR experience unless light conditions were optimal. Furthermore, the need to recalibrate digital compasses — allied to poor in-building functionality of GPS – means that under certain circumstances the level of location accuracy would not be sufficient for many potential corporate applications. As a result, the report stated that enterprise adoption would be limited in the medium term.
Other key findings from the report include:
More than 2.5 billion AR apps to be downloaded to smartphones and tablets each year by 2017, with games accounting for the largest share of downloads.
AR is increasingly being deployed in prototype wearable devices, with Google Glass the most high-profile innovation.
u-blox, the Swiss positioning and wireless module and chip company, announces UC530M, a tiny parallel GPS/GLONASS module with built-in antenna. The antenna module can be embedded in space-restricted environments because of its tiny footprint of 9.6 x 14.0 x 1.95 millimeters. The highly integrated SMT design reduces the need for external components and minimizes manufacturing costs, u-blox said.
“Location-aware functionality in ever-smaller consumer and industrial devices is a clear market trend. This presents an increasing challenge to OEMs,” said Thomas Nigg, vice president of product marketing at u-blox. “Manufacturers are confronted with the difficult task of providing fast and accurate positioning in compact devices, while time-to-market and price pressure call for minimal R&D effort and low cost. The new UC530M is built to address these requirements: a complete low-power, high performance multi-GNSS receiver with integrated antenna. The module is easy to integrate in a wide variety of devices cost-effectively.”
With high sensitivity, -165 dBm in tracking, and very low power consumption, typically only 66 mW average power consumption, the UC530M can be directly connected to a lithium battery, eliminating costly voltage regulators. Advanced low-power modes are also supported along with three days self-assistance support. Additional functionality includes a logger function which stores location information in internal memory. With a typical log interval of 15 seconds, log capacity can be up to 16 hours.
The integrated antenna of the UC530M exhibits significantly better radiation efficiency than small patch antennas, and performs well against larger and heavier patch antennas. Its circular radiation pattern brings flexibility to hardware designs, u-blox said. The optional connectivity to an external antenna extends the applicability of the module to a wider range of devices from handheld computers to asset tracking systems. The module is drop-in compatible with the UC530 GPS antenna module announced in June 2012.
Engineering samples of the UC530M modules are available in December 2012.
Topcon Positioning Systems has launched the second annual “How do you Topcon?” video contest with the slogan, “However and whenever you Topcon, we want to see it!”
The contest includes four categories:
Most innovative or creative use of Topcon equipment;
Funniest video or infomercial;
Best testimonial or “on-the-job” story;
The “wow” Factor.
The contest will run through December 15, 2012.
Participants will upload a short video (maximum length of three minutes) showing how they use Topcon products and services. Any use of Topcon equipment across all business segments — construction, survey, emerging business and agriculture — will be eligible. Prizes for the contest range from a preselected Topcon product, iPad or gift cards from $50 to $750.
“We want to engage our customers in a fun way through a social media forum and are finding that the video contest, and the recent ‘Topcon is Everywhere’ and ‘Spirit of Agriculture’ photo contests are excellent ways for everyone to get involved, from first-time-users of Topcon equipment to those who rely on it heavily for extensive projects,” Scott Langbein, director of product marketing said.
Esri has released ArcGIS for Windows Mobile 3.1, coinciding with the release of Trimble Positions field collection software. The Trimble Positions software suite extends the ArcGIS for Windows Mobile application and software developer kit (SDK) with support for high-accuracy GNSS mobile GIS data collection.
The Trimble Positions software suite is designed for users who require high-accuracy data collection workflows using Esri’s ArcGIS for Windows Mobile technology. The latest version of ArcGIS for Windows Mobile, combined with Trimble Positions software, simplifies field collection activities and requires little to no GNSS or GIS data collection experience, Esri said. ArcGIS for Windows Mobile and Trimble Positions support both real-time and postprocessing workflows, streamlining the process of collecting GPS data.
With ArcGIS for Windows Mobile, data collected with Trimble Positions can be automatically synced to an enterprise server when Trimble Positions Desktop is used to manage data from incoming field crews. Office administrators can easily check for new sessions, differentially correct the data, and verify that it meets accuracy requirements before updating the enterprise database at the touch of a button, Esri said.
Trimble has expanded coverage of its satellite-delivered Trimble RTX technology for surveyors to most of the world. Trimble has also introduced post-processing capability for its CenterPoint RTX positioning service for farmers. Both announcements were made at the Trimble Dimensions 2012 conference being held in Las Vegas this week.
RTX technology enables Trimble xFill, a new technique in RTK and VRS surveying that allows surveyors to continue working in the event the primary RTK or VRS correction stream is not available.
Trimble RTX technology, first introduced in 2011, combines real-time data and positioning algorithms to deliver centimeter accuracy around the world. While RTX technology is available worldwide via IP and cellular delivery methods, Trimble RTX has been available via satellite L-Band only in North and South America. Now, the expanded satellite coverage includes most of Europe, Russia, and the Commonwealth of Independent States (CIS), Africa, Asia, and Australasia.
Powered by Trimble RTX technology, Trimble xFill, a feature integrated into the new Trimble R10 GNSS Receiver, enables a new and innovative technique in RTK surveying, according to Trimble. It seamlessly “fills in” for RTK or VRS corrections for up to five minutes in the event of a temporary connection outage with the primary correction source. Minimizing downtime, Trimble xFill enables higher productivity for field survey crews, allowing them to continue working until radio or cellular connectivity is restored, Trimble said.
“The expanded coverage of satellite-delivered Trimble RTX technology further extends our commitment to providing different ways of realizing high accuracy positioning solutions,” said Patricia Boothe, general manager of Trimble’s Positioning Services Division. “The power of RTX is proven. Trimble RTX is the backbone of Trimble’s latest positioning innovations including the Trimble CenterPoint RTX service for farmers, the Trimble Pivot RTX App, and Trimble Pivot RTX-PP App infrastructure solutions and now, the Trimble xFill feature for surveyors.”
Trimble xFill feature allows satellite corrections to be delivered directly to the receiver with no need for additional equipment such as radios and antennas. With its built-in capability, the Trimble R10 automatically tracks these corrections and will use them when needed. Trimble xFill across the expanded satellite coverage area is expected to be available by late November 2012.
CenterPoint RTX Positioning Services. Enabled by Trimble RTX technology, CenterPoint RTX provides centimeter level positions in real time via satellite L-band and IP/cellular. The new post-processing capability delivers better than one-centimeter accuracy and is available worldwide.
Trimble CenterPoint RTX post-processing is a cloud-based service accessed through www.TrimbleRTX.com, allowing users around the globe to upload static GNSS observation data and receive positioning corrections calculated in the well-defined ITRF 2008 reference frame. The post-processed solution can be transformed to a variety of regional reference frames by selecting a coordinate system and tectonic plate.
“With the introduction of post-processing capability to the CenterPoint RTX portfolio, we continue to extend the breadth of the service,” said Patricia Boothe, general manager of Trimble’s Positioning Services Division. “CenterPoint RTX post-processing gives geospatial professionals another tool for their toolbox, utilizing Trimble’s globally available RTX technology to enable higher-accuracy positioning solutions.”
The open service allows any user to post process 10 data sessions per month.
The European Navigation Conference 2013 will be the 17th conference within the ENC series held under the auspices of the European Group of Institutes of Navigation (EUGIN). The conference will be hosted by the Austrian Institute of Navigation (AIN) and will take place April 23-25, 2013, in Vienna, Austria. The conference venue is located at the Austria Center Vienna next to the Vienna International Center.
The scientific program will be a combination of plenary lectures, parallel sessions and poster presentations. Each year the conference attracts researchers, students, policy makers, manufacturers, users, and service providers from all over the world. With the wide variety of topics in navigation and the expertise of the attending speakers, the aim is to bring together more than 600 experts.
The conference will focus on the present status as well as on future developments in navigation technologies and systems. The ENC 2013 will be a showcase for state-of-the-art technology and, more importantly, for innovations in the field of terrestrial and satellite-based navigation regarding positioning, trajectory determination, routing, guidance, surveillance, and other areas.
The program schedule will include ample time to visit the industrial and commercial exhibition which will run in parallel to the conference.
The official language of the symposium will be English. No simultaneous translation will be provided.
Firing on all cylinders — to use a slightly outmoded technological metaphor — GNSS moved forward on virtually every front in the past month. GPS made major advances both on the ground and in space, Galileo took a giant step, Compass continued on its roll, GLONASS has good news pending in only a day or two (knock on wood), and GAGAN is settling into space. But the best news of all is a very quiet, indeed somewhat hidden item: the UK patent applications against the interoperative GPS/Galileo signal design appear to have been dropped.
Let’s eat dessert first, since life is uncertain.
Patent Dispute Evaporates
Vague rumblings emerged throughout spring and summer this year that two British technologists, backed by the U.K. Ministry Defense, had filed patents on the future interoperable GPS and Galileo binary-offset carrier signal designs. If granted and enforced, the patents would have severely disrupted modernization plans for both systems and levied unexpected costs upon receiver manufacturers. And in fact a company called Ploughshare Innovations Ltd. Started dialing up said manufacturers and asking for payment of royalties, based on the patent filings.
After significant uproar and negotiations before and behind the scenes, it now appears that the initiative has been quietly scuttled. The file on application number 11/774,412, Modulation Signals for a Satellite Navigation System, on the U.S. Patent Office’s website, now reads “Expressly Abandoned — During Examination.” The status is dated September 16, 2012, some time ago, but that I’m aware of, no parties involved, whether as filers or negotiators, ever made any kind of announcement about it.
Checking the European Patent Office and its registry — which by the way is no trivial task of website navigation — I found a note under the docket for EP1830199, Modulations Signals for a Satellite Navigation System stating “Patent surrendered.” Dated September 24, 2012. A few days later, another note: “Lapsed in a contracting state announced via postgrant inform. From Nat. Office to EPO,” with further information to the effect of “lapse because of failure to submit a translation or the description or to pay the fee within the prescribed time limit.” And for good measure, a final docket not on October 3, “Lapsed due to resignation by the proprietor.”
However abstruse and arcane, we’ll take good news however we find it. Another bullet dodged.
GPS Ground Segment Benchmark
The GPS Directorate announced on October 26 that the U.S. Air Force and Raytheon have successfully met all requirements to enter into the engineering and manufacturing development phase of the Next-Generation Operational Control System (OCX). OCX will replace the current GPS operational control segment in managing the satellite constellation and providing command and control for all modernized signals.
OCX is being developed and fielded in blocks of GPS capability, to align with GPS III and military equipment deliveries.
OCX Block 0, also known as the Launch and Checkout System, scheduled to be available in the fourth quarter of Fiscal Year 2014, will allow OCX to support the launch of GPS III satellites.
OCX Block 1, scheduled to transition to operations in the first quarter of 2016, will deliver the operational capability to command and control the entire GPS constellation including GPS II and GPS III satellites. This block will also control the legacy civil and military signals, as well as two modernized civil and military signals, L2C and L5.
OCX Block 2 will specifically support advanced capabilities for civilian and military signals, the international civil signal, L1C, and the military signal, M-Code. OCX Block 2 is currently synchronized with modernized signal broadcast and timing.
GPS Block IIF-3 satellite.
GPS Block IIF Satellite Rises, Reaches Station, and Transmits
On October 11, The L5 transmitter aboard GPS Block IIF-3 satellite SVN65/PRN24 was switched on, transmitting the civilian safety-of-life GPS signal, designed to meet demanding requirements for safety-of-life transportation and other high-performance applications.
A day earlier, SVN65 began transmitting L1 and L2 signals as PRN24 on October 8. A number of stations of the International GNSS Service are tracking the satellite. As of press date for this magazine (October 25) the satellite is included in broadcast almanacs although it is set unhealthy and will continue to be so until satellite commissioning is completed. The satellite is drifting towards its designated orbital position of Slot 1 in Plane A.
The launch of the GPS Block IIF-3 satellite took place as scheduled October 4, aboard a United Launch Alliance Delta IV rocket from Cape Canaveral, Florida.
Galileo Turns Four. Validation Satellites, That Is.
The Galileo control room.
On October 12, a Soyuz launcher carrying two Galileo In-Orbit Validation (IOV) satellites deployed its twins into orbit within four hours after take-off, at close to 23,200 kilometers altitude. They join two earlier IOV spacecraft launched in October 2011. Once all four are operational in space, they will provide the minimum number of satellites required for navigational fixes — enabling system validation testing when all are visible in the sky.
A week after the dual liftoff from Kourou, French Guiana, the two satellites completed the critical Launch and Early Orbit Phase on October 19-20.
Satellites FM3 and FM4 satellites were handed over from the joint ESA/CNES Launch and Early Orbit Phase (LEOP) team in Toulouse, France, to the Galileo Control Centre, Oberpfaffenhofen, Germany, from where Spaceopal will manage operations of the Galileo constellation.
Three orbit maneuvers were conducted for each satellite to start them on drift orbits towards their operational positions, where they are expected to arrive on November 10 (FM3) and November 12 (FM4) after a series of drift-stop and fine-positioning movements.
The satellites were configured into a secure mode shortly after handover. While underway to their final positions, they will also undergo a series of tests to confirm the performance of their subsystems before switching on the payload.
The satellites were built by a consortium led by the Astrium division of EADS, which produced the platforms and has responsibility for the payloads, while Thales Alenia Space handled assembly and testing.
Compass up to Eleven
The two BeiDou-2/Compass satellites launched on September 18 reached their circular medium-Earth orbits on October 1 and started transmitting navigation signals. Several stations participating in the International GNSS Service’s Multi-GNSS Experiment as well as some in the Cooperative Network for GNSS Observation started tracking the satellites on September 26.
Although semi-official rumors had circulated that China was preparing for the Compass G6 (G2R) satellite launch on October 25, we have not found any announcement that the event has occurred.
The November issue of GPS World will appear in a few weeks’ time, with a cover story on “What Is Achievable with the Current Compass Constellation?” The technical article by Chinese researchers gives data from a 12-station tracking network distributed through China, the Pacific region, Europe, and Africa. It demonstrates the capacity of Compass with a constellation comprising four geostationary Earth-orbit (GEO) satellites and five inclined geosynchronous orbit (IGSO) satellites in operation. The regional system will be completed around the end of 2012 with a constellation of five GEOs, five IGSOs, and four medium-Earth orbit (MEO) satellites. By 2020 it will be extended into a global system.
GLONASS News in a Day or Two
As we go to e-press with this e-newsletter on October 30, we look forward to a Russian rocket rising on November 2 with a Luch data-relay satellite payload to service the the Russian satnav system. The second of a set of three geostationary satellites launched to reactivate Roscosmos’s Luch Multifunctional Space Relay System, it will also carry transponders for the System for Differential Correction and Monitoring (SDCM), Russia’s satellite-based augmentation system. The transponders will broadcast GNSS corrections on the standard GPS L1 frequency using C/A PRN codes assigned by the GPS Directorate. According to the most recent announcement, it will be positioned at 16 degrees West longitude, joining Luch-5A, already in an orbital slot at 95 degrees East longitude.
GAGAN Unfolding
The Indian Space Research Organization announced on October 3 that orbit-raising maneuvers placed the GSAT-10 satellite, launched September 30, in an orbit with 35,000-kilometer high orbit, with an orbit period of 23 hours 50 minutes, and a designated location of 83 degree East. GSAT-10 contains a payload to support the Indian GPS and GEO Augmented Navigation (GAGAN) satellite-based augmentation system. The satellite will likely use PRN code 128.
Another Dispute Headed for Resolution?
Finally, another pink dawn on the horizon. The European Union (EU) and China will reportedly meet in December in Paris to discuss overlapping radio frequencies both plan to use for their future encrypted government/military satellite navigation services.
The meeting will be conducted under what the Joint Statement on Space Technology Cooperation specifies as the ITU Framework. ITU is the International Telecommunication Union of Geneva, a United Nations affiliate that regulates satellite orbital slots and frequencies.
The statement was signed as an annex to a broader EU-China summit held September 20 in Brussels. The two sides continue collaboration on satellite navigation despite the signal conflict, which has been a subject of debate for at least two years.
The 27-nation EU and China have agreed to continue the China-Europe GNSS Technology Training and Cooperation Center.
Washington, D.C. — The Federal Communications Commission’s Enforcement Bureau today launched a dedicated jammer tip line – 1-855-55-NOJAM (or 1-855-556-6526) – to make it easier for the public to report the use or sale of illegal GPS, cell phone or other signal jammers. It is against the law for consumers to use, import, advertise, sell or ship a GPS or cell jammer or any other type of device that blocks, jams or interferes with authorized communications, whether on private or public property.
The FCC asks people to call the toll-free Jammer Tip Line immediately if:
you are aware of the ongoing use of a cell, GPS, or other signal jammer;
your employer operates a jammer in your workplace;
you observe a jammer in operation at your school or college;
you observe an advertisement for a jammer at a local store; or
you observe a jammer being operated on your local bus, train or other mass transit system.
“We need consumers to be our eyes and ears. Jammers do not just weed out noisy or annoying conversations and disable unwanted GPS tracking, they can prevent 9-1-1 and other emergency phone calls from getting through in a time of need,” Michele Ellison, chief of the Enforcement Bureau, said.
Calls to the Jammer Tip Line will be handled by experienced Enforcement Bureau staff. Callers are encouraged to provide as much detail as possible, including the time and location of the incident, a description of the jamming device (if available), and the name and contact information of the individual or business using or selling the device.
While callers may remain anonymous, the bureau urges callers to provide a contact phone number in case additional information is needed. “Every tip can make a difference,” Ellison said. “While our agents are actively pursuing these violations online and on the street, you can help. We encourage concerned parents, commuters, employees, and anyone else with credible information to tip us off. Working together, we can stop the spread of illegal jammers.
For more information, Frequently Asked Questions about cell, GPS, and Wi-Fi jammers are available at www.fcc.gov/jammers, or email [email protected].
Figure 1. Distribution of the GPS+COMPASS tracking network established by the GNSS Research Center at Wuhan University and used as test network in this study.
Data from a tracking network with 12 stations in China, the Pacific region, Europe, and Africa demonstrates the capacity of Compass with a constellation comprising four geostationary Earth-orbit (GEO) satellites and five inclined geosynchronous orbit (IGSO) satellites in operation. The regional system will be completed around the end of 2012 with a constellation of five GEOs, five IGSOs, and four medium-Earth orbit (MEO) satellites. By 2020 it will be extended into a global system.
By Maorong Ge, Hongping Zhang, Xiaolin Jia, Shuli Song, and Jens Wickert
China’s satellite navigation system Compass, also known as BeiDou, has been in deveopment for more than a decade. According to the China National Space Administration, the development is scheduled in three steps: experimental system, regional system, and global system.
The experimental system was established as the BeiDou-1 system, with a constellation comprising three satellites in geostationary orbit (GEO), providing operational positioning and short-message communication. The follow-up BeiDou-2 system is planned to be built first as a regional system with a constellation of five GEO satellites, five in inclined geosynchronous orbit (IGSO), and four in medium-Earth orbit (MEO), and then to be extended to a global system consisting of five GEO, three IGSO, and 27 MEO satellites. The regional system is expected to provide operational service for China and its surroundings by the end of 2012, and the global system to be completed by the end of 2020.
The Compass system will provide two levels of services. The open service is free to civilian users with positioning accuracy of 10 meters, timing accuracy of 20 nanoseconds (ns) and velocity accuracy of 0.2 meters/second (m/s). The authorized service ensures more precise and reliable uses even in complex situations and probably includes short-message communications.
The fulfillment of the regional-system phase is approaching, and the scheduled constellation is nearly completed. Besides the standard services and the precise relative positioning, a detailed investigation on the real-time precise positioning service of the Compass regional system is certainly of great interest.
With data collected in May 2012 at a regional tracking network deployed by Wuhan University, we investigate the performance of precise orbit and clock determination, which is the base of all the precise positioning service, using Compass data only. We furthermore demonstrate the capability of Compass precise positioning service by means of precise point positioning (PPP) in post-processing and simulated real-time mode.
After a short description of the data set, we introduce the EPOS-RT software package, which is used for all the data processing. Then we explain the processing strategies for the various investigations, and finally present the results and discuss them in detail.
Tracking Data
The GNSS research center at Wuhan University is deploying its own global GNSS network for scientific purposes, focusing on the study of Compass, as there are already plenty of data on the GPS and GLONASS systems. At this point there are more than 15 stations in China and its neighboring regions.
Two weeks of tracking data from days 122 to 135 in 2012 is made available for the study by the GNSS Research Center at Wuhan University, with the permission of the Compass authorities. The tracking stations are equipped with UR240 dual-frequency receivers and UA240 antennas, which can receive both GPS and Compass signals, and are developed by the UNICORE company in China. For this study, 12 stations are employed. Among them are seven stations located in China: Chengdu (chdu), Harbin (hrbn), HongKong (hktu), Lhasa (lasa), Shanghai (sha1), Wuhan (cent) and Xi’an (xian); and five more in Singapore (sigp), Australia (peth), the United Arab Emirates (dhab), Europa (leid) and Africa (joha). Figure 1 shows the distribution of the stations, while Table 1 shows the data availability of each station during the selected test period.
Table 1. Data availability of the stations in the test network.
There were 11 satellites in operation: four GEOs (C01, C03, C04, C05), five IGSOs (C06, C07, C08, C09, C10), and two MEOs (C11, C12). During the test time, two maneuvers were detected, on satellite C01 on day 123 and on C06 on day 130. The two MEOs are not included in the processing because they were still in their test phase.
Software Packages
The EPOS-RT software was designed for both post-mission and real-time processing of observations from multi-techniques, such as GNSS and satellite laser ranging (SLR) and possibly very-long-baseline interferometry (VLBI), for various applications in Earth and space sciences. It has been developed at the German Research Centre for Geosciences (GFZ), primarily for real-time applications, and has been running operationally for several years for global PPP service and its augmentation. Recently the post-processing functions have been developed to support precise orbit determinations of GNSS and LEOs for several ongoing projects.
We have adapted the software package for Compass data for this study. As the Compass signal is very similar to those of GPS and Galileo, the adaption is straight-forward thanks to the new structure of the software package. The only difference to GPS and Galileo is that recently there are mainly GEOs and IGSOs in the Compass system, instead of only MEOs. Therefore, most of the satellites can only be tracked by a regional network; thus, the observation geometry for precise orbit determination and for positioning are rather different from current GPS and GLONASS.
Figure 2 shows the structure of the software package. It includes the following basic modules: preprocessing, orbit integration, parameter estimation and data editing, and ambiguity-fixing. We have developed a least-square estimator for post-mission data processing and a square-root information filter estimator for real-time processing.
Figure 2. Structure of the EPOS-RT software.
GPS Data Processing
To assess Compass-derived products, we need their so-called true values. The simplest way is to estimate the values using the GPS data provided by the same receivers.
First of all, PPP is employed to process GPS data using International GNSS Service (IGS) final products. PPP is carried out for the stations over the test period on a daily basis, with receiver clocks, station coordinates, and zenith tropospheric delays (ZTD) as parameters. The repeatability of the daily solutions confirms a position accuracy of better than 1 centimeter (cm), which is good enough for Compass data processing. The station clock corrections and the ZTD are also obtained as by-products.
The daily solutions are combined to get the final station coordinates. These coordinates will be fixed as ground truth in Compass precise orbit and clock determination. Compass and GPS do not usually have the same antenna phase centers, and the antenna is not yet calibrated, thus the corresponding corrections are not yet available. However, this difference could be ignored in this study, as antennas of the same type are used for all the stations.
Orbit and Clock Determination
For Compass, a three-day solution is employed for precise orbit and clock estimation, to improve the solution strength because of the weak geometry of a regional tracking network. The orbits and clocks are estimated fully independent from the GPS observations and their derived results, except the station coordinates, which are used as known values.
The estimated products are validated by checking the orbit differences of the overlapped time span between two adjacent three-day solutions. As shown in Figure 3, orbit of the last day in a three-day solution is compared with that over the middle day of the next three-day solution. The root-mean-square (RMS) deviation of the orbit difference is used as index to qualify the estimated orbit.
Figure 3. Three-day solution and orbit overlap. The last day of a three-day solution is compared with the middle day of the next three-day solution.
In each three-day solution, the observation models and parameters used in the processing are listed in Table 2, which are similar to the operational IGS data processing at GFZ except that the antenna phase center offset (PCO) and phase center variation (PCV) are set to zero for both receivers and satellites because they are not yet available.
Satellite force models are also similar to those we use for GPS and GLONASS in our routine IGS data processing and are listed in Table 2. There is also no information about the attitude control of the Compass satellites. We assume that the nominal attitude is defined the same as GPS satellite of Block IIR.
Table 2. Observation and force models and parameters used in the processing.
Satellite Orbits. Figure 4 shows the statistics of the overlapped orbit comparison for each individual satellite. The averaged RMS in along- and cross-track and radial directions and 3D-RMS as well are plotted. GEOs are on the left side, and IGSOs on the right side; the averaged RMS of the two groups are indicated as (GEO) and (IGSO) respectively. The RMS values are also listed in Table 3.
As expected, GEO satellites have much larger RMS than IGSOs. On average, GEOs have an accuracy measured by 3D-RMS of 288 cm, whereas that of IGSOs is about 21 cm.
As usual, the along-track component of the estimated orbit has poorer quality than the others in precise orbit determination; this is evident from Figure 4 and Table 3. However, the large 3D-RMS of GEOs is dominated by the along-track component, which is several tens of times larger than those of the others, whereas IGSO shows only a very slight degradation in along-track against the cross-track and radial. The major reason is that IGSO has much stronger geometry due to its significant movement with respect to the regional ground-tracking network than GEO.
Figure 4. Averaged daily RMS of all 12 three-day solutions. GEOs are on the left side and IGSOs on the right. Their averages are indicated with (GEO) and (IGSO), respectively.Table 3. RMS of overlapped orbits (unit, centimeters).
If we check the time series of the orbit differences, we notice that the large RMS in along-track direction is actually due to a constant disagreement of the two overlapped orbits. Figure 5 plots the time series of orbit differences for C05 and C06 as examples of GEO and IGSO satellites, respectively. For both satellites, the difference in along-track is almost a constant and it approaches –5 meters for C05.
Note that GEO shows a similar overlapping agreement in cross-track and radial directions as IGSO.
Figure 5. Time series of orbit differences of satellite C05 and C06 on the day 124 2012. A large constant bias is in along-track, especially for GEO C05.
Satellite Clocks. Figure 6 compares the satellite clocks derived from two adjacent three-day solutions, as was done for the satellite orbits. Satellite C10 is selected as reference for eliminating the epoch-wise systematic bias. The averaged RMS is about 0.56 ns (17 cm) and the averaged standard deviation (STD) is 0.23 ns (7 cm). Satellite C01 has a significant larger bias than any of the others, which might be correlated with its orbits.
From the orbit and clock comparison, both orbit and clock can hardly fulfill the requirement of PPP of cm-level accuracy. However, the biases in orbit and clock are usually compensatable to each other in observation modeling. Moreover, the constant along-track biases produce an almost constant bias in observation modeling because of the slightly changed geometry for GEOs. This constant bias will not affect the phase observations due to the estimation of ambiguity parameters. Its effect on ranges can be reduced by down-weighting them properly. Therefore, instead of comparing orbit and clock separately, user range accuracy should be investigated as usual. In this study, the quality of the estimated orbits and clocks is assessed by the repeatability of the station coordinates derived by PPP using those products.
Figure 6. Statistics of the overlap differences of the estimated receiver and satellite clocks. Satellite C10 is selected as the reference clock.
Precise Point Positioning
With these estimates of satellite orbits and clocks, PPP in static and kinematic mode are carried out for a user station that is not involved in the orbit and clock estimation, to demonstrate the accuracy of the Compass PPP service.
In the PPP processing, ionosphere-free phase and range are used with proper weight. Satellite orbits and clocks are fixed to the abovementioned estimates. Receiver clock is estimated epoch-wise, remaining tropospheric delay after an a priori model correction is parameterized with a random-walk process. Carrier-phase ambiguities are estimated but not fixed to integer. Station coordinates are estimated according to the positioning mode: as determined parameters for static mode or as epoch-wise independent parameters for kinematic mode.
Data from days 123 to 135 at station CHDU in Chengdu, which is not involved in the orbit and clock determination, is selected as user station in the PPP processing. The estimated station coordinates and ZTD are compared to those estimated with GPS data, respectively.
Static PPP. In the static test, PPP is performed with session length of 2 hours, 6 hours, 12 hours, and 24 hours. Figure 7 and Table 4 show the statistics of the position differences of the static solutions with various session lengths over days 123 to 125.
The accuracy of the PPP-derived positions with 2 hours data is about 5 cm, 3 cm, and 10 cm in east, north, and vertical, compared to the GPS daily solution. Accuracy improves with session lengths. If data of 6 hours or longer are involved in the processing, position accuracy is about 1 cm in east and north and 4 cm in vertical. From Table 4, the accuracy is improved to a few millimeters in horizontal and 2 cm in vertical with observations of 12 to 24 hours. The larger RMS in vertical might be caused by the different PCO and PCV of the receiver antenna for GPS and Compass, which is not yet available.
Figure 7. Position differences of static PPP solutions with session length of 2 hours, 6 hours, 12 hours, and 24 hours compared to the estimates using daily GPS data for station CHDU.Table 4. RMS of PPP position with different session length.
Kinematic PPP. Kinematic PPP is applied to the CHDU station using the same orbit and clock products as for the static positioning for days 123 to 125 in 2012.
The result of day 125 is presented here as example. The positions are estimated by means of the sequential least-squares adjustment with a very loose constraint of 1 meter to positions at two adjacent epochs. The result estimated with backward smoothing is shown in Figure 8. The differences are related to the daily Compass static solution. The bias and STD of the differences in east, north, and vertical are listed in Table 5. The bias is about 16 mm, 13 mm, and 1 mm, and the STD is 10 mm, 14 mm and 55 mm, in east, north, and vertical, respectively.
Figure 8. Position differences of the kinematic PPP and the daily static solution, and number of satellites observed.Table 5. Statistics of the position differences of the kinematic PPP in post-processing mode and the daily solution. (m)
Compass-Derived ZTD. ZTD is a very important product that can be derived from GNSS observations besides the precise orbits and clocks and positions. It plays a crucial role in meteorological study and weather forecasting.
ZTD at the CHDU station is estimated as a stochastic process with a power density of 5 mm √hour by fixing satellite orbits, clocks, and station coordinates to their precisely estimated values, as is usually done for GPS data.
The same processing procedure is also applied to the GPS data collected at the station, but with IGS final orbits and clocks. The ZTD time series derived independently from Compass and GPS observations over days 123 to 125 in 2012 and their differences are shown on Figure 9.
Figure 9. Comparison of ZTD derived independently from GPS and COMPASS observations. The offset of the two time series is about -14 mm (GPS – COMPASS) and the STD is about 5 mm.
Obviously, the disagreement is mainly caused by Compass, because GPS-derived ZTD is confirmed of a much better quality by observations from other techniques. However, this disagreement could be reduced by applying corrected PCO and PCV corrections of the receiver antennas, and of course it will be significantly improved with more satellites in operation.
Simulated Real-Time PPP Service
Global real-time PPP service promises to be a very precise positioning service system. Hence we tried to investigate the capability of a Compass real-time PPP service by implementing a simulated real-time service system and testing with the available data set.
We used estimates of a three-day solution as a basis to predict the orbits of the next 12 hours. The predicted orbits are compared with the estimated ones from the three-day solution. The statistics of the predicted orbit differences for the first 12 hours on day 125 in 2012 are shown on Figure 10.
From Figure 10, GEOs and IGSOs have very similar STDs of about 30 cm on average. Thus, the significantly large RMS, up to 6 meters for C04 and C05, implies large constant difference in this direction. The large constant shift in the along-track direction is a major problem of the current Compass precise orbit determination. Fortunately, this constant bias does not affect the positioning quality very much, because in a regional system the effects of such bias on observations are very similar.
Figure 10. RMS (left) and STD (right) of the differences between predicted and estimated orbits.
With the predicted orbit hold fixed, satellite clocks are estimated epoch-by-epoch with fixed station coordinates. The estimated clocks are compared with the clocks of the three-day solution, and they agree within 0.5 ns in STD. As the separated comparison of orbits and clocks usually does not tell the truth of the accuracy of the real-time positioning service, simulated real-time positioning using the estimated orbits and clocks is performed to reveal the capability of Compass real-time positioning service.
Figure 11 presents the position differences of the simulated real-time PPP service and the ground truth from the static daily solution. Comparing the real-time PPP result in Figure 11 and the post-processing result in Figure 8, a convergence time of about a half-hour is needed for real-time PPP to get positions of 10-cm accuracy. Afterward, the accuracy stays within ±20 cm and gets better with time. The performance is very similar to that of GPS because at least six satellites were observed and on average seven satellites are involved in the positioning. No predicted orbit for C01 is available due to its maneuver on the day before. Comparing the constellation in the study and that planned for the regional system, there are still one GEO and four MEOs to be deployed in the operational regional system. Therefore, with the full constellation, accuracy of 1 decimeter or even of cm-level is achievable for the real-time precise positioning service using Compass only.
Figure 11. Position differences of the simulated real-time PPP and the static daily PPP. The number of observed satellites is also plotted.
Summary
The three-day precise orbit and clock estimation shows an orbit accuracy, measured by overlap 3D-RMS, of better than 288 cm for GEOs and 21 cm for IGSOs, and the accuracy of satellite clocks of 0.23 ns in STD and 0.56 in RMS. The largest orbit difference occurs in along-track direction which is almost a constant shift, while differences in the others are rather small.
The static PPP shows an accuracy of about 5 cm, 3 cm, and 10 cm in east, north, and vertical with two hours observations. With six hours or longer data, accuracy can reach to 1 cm in horizontal and better than 4 cm in vertical. The post-mission kinematic PPP can provide position accuracy of 2 cm, 2 cm, and 5 cm in east, north, and vertical. The high quality of PPP results suggests that the orbit biases, especially the large constant bias in along-track, can be compensated by the estimated satellite clocks and/or absorbed by ambiguity parameters due to the almost unchanged geometry for GEOs.
The simulated real-time PPP service also confirms that real-time positioning services of accuracy at 1 decimeter-level and even cm–level is achievable with the Compass constellation of only nine satellites. The accuracy will improve with completion of the regional system.
This is a preliminary achievement, accomplished in a short time. We look forward to results from other colleagues for comparison. Further studies will be conducted to validate new strategies for improving accuracy, reliability, and availability. We are also working on the integrated processing of data from Compass and other GNSSs. We expect that more Compass data, especially real-time data, can be made available for future investigation.
UA240 OEM card made by Unicore company and used in Compass reference stations.
Acknowledgments
We thank the GNSS research center at Wuhan University and the Compass authorities for making the data available for this study.
The material in this article was first presented at the ION-GNSS 2012 conference.
Maorong Ge received his Ph.D. in geodesy at Wuhan University, China. He is now a senior scientist and head of the GNSS real-time software group at the German Research Centre for Geosciences (GFZ Potsdam).
Hongping Zhang is an associate professor of the State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing at Wuhan University, and holds a Ph.D. in GNSS applications from Shanghai Astronomical Observatory. He designed the processing system of ionospheric modeling and prediction for the Compass system.
Xiaolin Jia is a senior engineer at Xian Research Institute of Surveying and Mapping. He received his Ph.D. from the Surveying and Mapping College of Zhengzhou Information Engineering University.
Shuli Song is an associate research fellow. She obtained her Ph.D. from the Shanghai Astronomical Observatory, Chinese Academy of sciences.
Jens Wickert obtained his doctor’s degree from Karl-Franzens-University Graz in geophysics/meteorology. He is acting head of the GPS/Galileo Earth Observation section at the German Research Center for Geosciences GFZ at Potsdam.
