The seven-minute video explains in simple terms how important GPS has become to everyday life — for aircraft and ship navigation, global financial transactions, precision agriculture, weather forecasting, disaster relief, and, of course, smartphones.

Smith’s photograph was taken at 21:58:38 UTC (start) with a Canon EOS 450D Digital Rebel camera with an 18-55mm zoom lens. The camera settings were: focal length 55mm, aperture f/5.6, and an exposure of 8 seconds at an ISO value of 1600. Two images are shown below: the original, as obtained from the camera, and a greyscale image with edge enhancement.

The Centaur can be seen traveling left to right and starts its track as it crosses the constellation of Cygnus. There’s a slight wobble at the beginning as the shutter release was pressed. The glow at the bottom of the frame is from a streetlight. The elevation angle of the Centaur was approximately 12 degrees.

SVN66 will operate as PRN27 and it will eventually occupy the C-2 orbital slot, replacing SVN33/PRN03, a Block IIA satellite launched in 1996. SVN66 is currently in a drift orbit about 400 kilometers above the operational constellation. It should reach the C-2 slot within a few days from now. The satellite has already been added to the broadcast almanac although it has not yet started to transmit standard signals. It is currently marked as unhealthy in the almanac and will remain so, even after standard signals are switched on, until testing is completed sometime this summer.

Centaur upper stage with the payload still attached, original photo. Photo credit: Andy Smith

The same photo digitally enhanced:

Digitally enhanced photo. Photo credit: Andy Smith

Photo credit: Pat Corkery, United Launch Alliance.

A U.S. Air Force Global Positioning System satellite built by Boeing was successfully launched May 15. The fourth GPS IIF satellite, Space Vehicle Number (SVN) 66, was carried aboard a United Launch Alliance Atlas V Launch Vehicle at 5:38 p.m. EDT (21:38 UTC) May 15 from Cape Canaveral Air Force Station, Florida.

The new capabilities of the IIF satellites will provide greater navigational accuracy through improvements in atomic clock technology; a more robust signal for commercial aviation and safety-of-life applications, known as the new third civil signal (L5); and a 12-year design life providing long-term service. These upgrades improved anti-jam capabilities for the warfighter and improved security for military and civil users around the world, the Air Force said in a statement.

The Atlas rocket took off on schedule. The satellite was released from the Centaur upper stage at T+ 3 hours, 23 minutes and 52.8 seconds or about 01:02 UTC on May 16. Details on the Block IIF satellites and the Atlas rocket can be found here.

“I’m extremely pleased with today’s launch and delighted to be part of this mission that enhances our nation’s critical GPS capability. Thanks to the superb efforts of the of the 45th and 50th Space Wings, United Launch Alliance, our industry partners, the Atlas V and GPS IIF launch teams, the GPS IIF-4 mission was successfully carried out,” said Col. Bernie Gruber, director of the Space and Missile Systems Center’s Global Positioning Systems Directorate.

“The GPS constellation remains healthy and continues to meet and exceed the performance standards to which the satellites were built. Our goal is to deliver sustained, reliable GPS capabilities to America’s warfighters, our allies and civil users around the world, and this is done by maintaining GPS performance, fielding new capabilities and developing more robust modernized capabilities for the future,” said Colonel Gruber.

Here are videos of the launch:


Opening photo by Pat Corkery, United Launch Alliance.

Photos show the launch of the U.S. Air Force’s GPS IIF-4 satellite from the Kennedy Space Center and Cape Canaveral Air Force Station.

Sun Jiadong, chief designer of BDS and an academician of the Chinese Academy of Sciences, made his comments in an interview with The Beijing News, as reported by the Chinese government’s website.

He added that this compatibility is the only way to ensure the protection of national information. “Safety issues abound in economic areas,” said Sun. “Ordinary people may have few concerns about the security of information but it is of vital significance.”

The development of Beidou also largely depends on the government’s involvement. “Even though the enterprises spare no effort in developing the system, the products they make would not be available for mass production, which will in turn be reflected by the prices. The government has to promote the research and development of the system,” Sun said. Sun cited the governments of Beijing, Shanghai, and Guangzhou as examples of local governments that were effectively helping to develop the BDS.

The use of Beidou could go beyond basic navigation functions and extend to the civilian market. It would take longer for the BDS to be available for civilians, said Sun. The use of Beidou on mobile phones relies on the development of a small and power-efficient chip. Otherwise the phone cannot be used.

When asked about when and how the cost of developing the BDS will be recovered, Sun reiterated that Beidou was developed to ensure the security of national information, and not to make profits.

The Beidou global navigation system will be available by 2020 with the launching of more than 30 satellites.

The NexNav Circuit Card Assembly (CCA) will integrate with FreeFlight’s upgraded automatic dependent surveillance-broadcast (ADS-B) avionics to fulfill the requirements of the second phase of the FAA Capstone Project.

“This is an excellent example of how we are working closely with FreeFlight Systems to create state-of-the-art NextGen solutions that are not only meeting upcoming mandate requirements but doing it in a cost effective manner,” stated Hal Adams, Chief Operating Officer for Accord Technology, LLC.

The Accord Technology NexNav product line revolves around two key receivers, NexNav mini and NexNav MAX. The receivers are at the heart of embedded customer solutions whether as a Circuit Card Assembly (CCA) or embedded in the Line Replacement Unit (LRU) as a stand-alone GPS solution.

NexNav mini was the industry’s first GPS receiver and sensor qualified to fully support the known worldwide and U.S. FAA ADS-B GPS source requirements The NexNav mini and MAX are compatible with EGNOS and other Satellite Based Augmentation Systems (SBAS) to the extent they are is compatible with WAAS.

When I arrived in Denver, my plan was to meet Tim Smith (GPS Coordinator for the U.S. National Park Service) and travel to the Bakerville GPS test site in the Rocky Mountains, which was at about ~11,000 feet in elevation. My intent was to test the CORS Streaming and PBO real-time streaming that I discussed last month to better understand the accuracy and reliability of those services.

I arrived at the Denver airport early on a Monday ready to rock and roll into the Rockies with some high-precision GNSS equipment. As it turned out, I was denied. In Colorado, the weather is dynamic. It was quickly degrading when I arrived in Denver. Snow was definitely in my future for the next few days. Tim made the decision that we shouldn’t travel to Bakerville. The reason for Tim’s trepidation wasn’t necessarily due to the weather in Bakerville, but rather that the I-70 Interstate might turn into a parking lot and we’d be stuck in traffic for a few hours. Fair enough. The backup plan was to do some local testing in the parking lot adjacent to Tim’s office in Denver.

Tim invited Mel Philbrook to join us. Mel is a long-time GNSS technologist who works for the local Trimble dealer. He brought an SUV full of Trimble GNSS equipment, including one of the new R10 GNSS units as well as a GeoXH handheld with an external antenna.

Tim Smith using a Trimble R10 with CORS Streaming RTK data.

Mel and Eric with some of the GNSS gear.

Mel also had an Intuicom RTK Bridge in the trunk of his SUV that facilitated the different sources of RTK reference data we could use. He could switch from CORS Streaming to the local VRS via NTRIP to UHF at the flip of a switch, sending corrections to both the R10 and the GeoXH. I was particularly interested in seeing how the units performed using CORS Streaming, which is/was a free RTK service (single baseline) that was in beta test phase. In Oregon, I don’t have access to CORS Streaming because the only CORS Streaming station west of the Mississippi River is in Boulder, Colorado. The station is TMGO (Table Mountain CORS).

The baseline distance from TMGO to our location was about 55 km. The R10 was reporting a horizontal precision of about 4 cm. Not bad for a 55-km baseline. I didn’t compare the results to a survey mark (shame on me, but keep reading because I get to that) so I’m trusting the R10’s precision estimate. Tim said he’s run the test before using a GeoXH and a longer baseline and saw sub 10-cm horizontal precision. It’s not what the typical person using short baseline or RTK network is accustomed to, but for the high-precision GIS user who’s mapping utility, transportation, and infrastructure, that’s pretty darn good.

Tim, Mel and I spent an hour or so messing around with the equipment before packing it up. Not a very scientific study, but it confirmed that CORS Streaming was accessible via NTRIP and reasonably accurate.

In the meantime, the snow wasn’t letting up. This is the view as I was leaving Tim’s office to head to Boulder for the Space Weather Workshop:

Leaving Tim’s office. There was no snow when I arrived.

I wasn’t finished with my CORS Streaming testing yet. My experience at Tim’s office gave me enough confidence to allocate time later in the week to conduct a more detailed test after the Space Weather Workshop. Hopefully, the weather would cooperate (call me a fair-weather field guy).

Space Weather Workshop

Every April, NOAA’s Space Weather Prediction Center in Boulder hosts the Space Weather Workshop (SWW), a gathering that has evolved into the leading conference in the U.S. for space weather-related topics. It attracts attendees, experts and speakers from all over the world. The discussion isn’t centered on GNSS, but GNSS certainly is a topic that is discussed. This year’s central topic was the electric power grid. You can view the SWW program here.

Believe it or not, this month (May 2013) was the predicted “solar maximum” for the current solar cycle (Solar Cycle 24, an 11-year cycle). However, Solar Cycle 24 has been unexpectedly weak. See the following slide presented by Doug Bisecker of the Space Weather Prediction Center. Doug is the Chairman of the Solar Cycle 24 Prediction Panel. His question, “Is there any chance we can still salvage some respectability?” speaks volumes about the difficulty in predicting space weather.

Source: Doug Bisecker presentation at the 2013 Space Weather Workshop

From the above, you can see the actual number of sun spot occurrence has been significantly less than predicted. Although sun spots aren’t what cause GNSS receivers to have problems, sun spots can indicate the amount of solar activity, which can be related to geomagnetic storms. Geomagnetic storms disturb the ionosphere and are the events that cause the most problems for GNSS receivers. Looking at the top chart above, you can see the difference in activity between the last solar maximum (peaked in early 2002) and today. The difference is clearly significant.

Does this mean we, the high-precision GNSS users, get a free pass on Solar Cycle 24?

Not at all.

Historically speaking, the most extreme geomagnetic storms (e.g., Oct/Nov 2002) have occurred after the solar maximum so our sensitivity to this issue should be keen for the next two years. Furthermore, there are orders of magnitude more high-precision GNSS receivers being used than ever before, and in mission-critical applications such as auto-steer in machine control (agriculture, construction, etc.). Most GNSS high-precision users today haven’t experienced the effects of an extreme geomagnetic storm. For a short primer on the effects of solar activity on GNSS/GPS, you might want to take a look at this article I wrote in 2008 as well Richard Langley’s 2011 Innovation column “GNSS and the Ionosphere.” In addition to the content, they both contain some valuable links to relevant articles.

In line with a goal of the workshop, a panel of GNSS professionals looked at issues that users face as they go about their business at solar max. The panel was “Global Navigation Satellite System (GNSS) Services: Research Needed to Fill Operational Gaps.” Joe Kunches (SWPC) moderated the panel that included Dr. Geoff Crowley (Astra), Dr. Anthea Coster (MIT), Capt. Steven Miller (USAF) and myself. We highlighted precision GNSS, satellite navigation for commercial aviation (ADS-B), and current work to better understand the errors the ionosphere imposes on user activities.

Something else I learned at the conference was how tough ionospheric scintillation is on GNSS receivers in Brazil. I feel for those users. When I mentioned I was traveling to Chile for an RTK project, the scientists said it is worse in Chile than the U.S., but still not as bad as Brazil. I’ll be very interested to experience how different it is than the U.S. (or other parts of the world where I’ve traveled).

I keep a pretty close eye on space weather and in contact with NOAA’s Space Weather Prediction Center. When I hear of a space weather event that may affect high-precision GNSS/GPS receivers, I send out a Tweet with the hashtag #SolarActivity. You can follow me on Twitter at https://twitter.com/GPSGIS_Eric.

From Space Weather Back to Local Weather

As the week progressed during the Space Weather Workshop, the snow continued. Boulder looked like Christmas in April.

Christmas in April, Boulder, Colorado.

I really wanted to spend some more time in the field to test the accuracy of the NGS’s CORS Streaming service and I was running out of time. In order to perform the test the way I wanted, I needed to find a local NGS survey mark that was observed using GPS. I checked out the NGS survey mark database and got lucky. There was one (PID = KK2060) located on a vista point parking area off of Highway 36 on the way from my hotel to the Space Weather Workshop. I couldn’t have asked for a better or more convenient survey mark location. I was planning to use a Bluetooth GNSS receiver so I could actually collect data while sitting in my car.

KK2060 Survey Mark along Highway 36

On Thursday morning, Mother Nature cleared her skies for me so I drove to the vista point. Remember, there’s a couple of feet of snow on the ground, so I was really hoping to see some kind of wood lathe that would get me close to the survey mark (no, I didn’t preload the KK2060 coords in my GPS L). Fortunately, a wood stake was near the survey mark. However, I didn’t have a shovel or a metal detector so it was either using my hands to shovel and search under two feet of snow for the mark, or…thanks to the rental car company, the car came with a healthy-sized windshield scraper. After 15 minutes of digging in the snow with a windshield scraper, I found KK2060. I’m sure to the people parked on the vista enjoying the view; I looked very suspicious using a windshield scraper to dig a hole in the snow. I wouldn’t have been surprised if a state trooper had shown up.

KK2060 recovered from under two feet of snow with a windshield scraper.

My final challenge was…no tripod or tribrach. I travel light and didn’t want to pack a set and, of course, I forgot to ask Tim if I could borrow a set. It’s never a good idea to set a GNSS antenna directly on the ground, but the antenna was small (<3” in diameter) and I did have a 5” diameter ground plane with about a 1” post. I was able to place it over the survey mark with reasonable confidence.

3″ diameter L1/L2/GLONASS antenna on a 5″ ground plane centered over KK2060.

As I mentioned before, I was using a Bluetooth GNSS receiver (GPS L1/L2, GLONASS), the SXBlue III GNSS.

SXBlue III GNSS bluetooth receiver

To collect the data, I was using an SXPad handheld with an AT&T SIM card for the Internet connection. For data-collection software, I used VisualGPSce, a free GPS data-collection program that collects and displays raw NMEA data. Although it doesn’t display enough digits of precision for the horizontal position, it accomplishes the simple task of collecting NMEA-formatted data without applying any transformation so I get the raw NMEA-formatted data from the receiver. It also displays some useful information such as PDOP, RTK indicator and elevation.

VisualGPSce running on an SXPad data collector collecting RTK data.

The last piece of data-collection software I used was a free NTRIP client software written by the SXBlue people called SXBlue RTN. I needed an NTRIP client software to access the CORS Streaming mount point. The software manages the IP address, port and login/pwd of the CORS Streaming system.

Logging into the NGS CORS Streaming site was painless, and within a few seconds I had an RTK FIXed position from the GNSS receiver, all from the comfort of my rental car, thanks to long-range Bluetooth. I collected ~45 minutes of NMEA data (1-Hz data rate) without interruption.

When I returned to the office, I began the process of comparing the results from CORS Streaming to the NGS survey mark coordinate. I checked with NGS and they reported that CORS Streaming is referenced to the ITRF00 (epoch 1997.0) datum. The KK2060 coordinate is published in NAD83/2011 (epoch 2010.0). I needed to reconcile the datum difference before performing any analysis so I used the NGS HTDP (Horizontal Time Dependent Positioning) online tool to accomplish this.

Finally, I used NMEA Analyzer (custom-built software for performing statistical analysis on GNSS NMEA data to NSSDA horizontal accuracy standards) to calculate accuracy (not precision) values of the data. I set up the NMEA Analyzer software to randomly select 200 epochs out of the ~2,700 collected to mitigate any bias due to filtering or other receiver “tricks”. Following are the horizontal results:

Not bad for an antenna sitting on the ground and an 18-km baseline using a $6,000 GNSS receiver and a free RTK base station. Folks, this is the direction that GNSS technology is heading. The continued proliferation of high-precision GNSS infrastructure (RTK networks, real-time PPP, etc.) and the falling prices of RTK GNSS receivers will dramatically increase the availability of high-precision technology to those who previously could not afford to make the investment.

I didn’t get a chance to test the PBO real-time streaming while I was in Colorado, but fortunately there are many PBO real-time stations that I can test from the comfort of my home office here in Oregon. In fact, there are so many in Oregon and Washington that I can test many different baseline distances to understand what accuracy users can expect. Look for my test results on that sometime this summer.

National Geodetic Survey (NGS) Suffering

It’s likely that you aren’t an NDGPS user, but you might still be affected if the NDGPS is decommissioned. There are a total of 86 NDGPS stations across the Continental U.S., Alaska and Hawaii. As well as being NDGPS signal broadcasters, they are also part of the NGS CORS program that is used by the NGS’s OPUS online post-processing service. If you are using OPUS or NGS CORS for post-processing, you might be using NDGPS CORS data and not realize it. Following is a map of all NDGPS stations in the U.S.:

U.S. NDGPS coverage map.

If you’re interested in reading an explanation from the U.S. Coast Guard and Department of Transportation about the request for public comment and submitting a comment, click here. To be considered, comments must be submitted by July 15.

In 2011 the European GNSS Agency (GSA) awarded GMV the EEGS2 project (EGNOS Extension to Eastern Europe). The main objective of the project is to demonstrate through flight trials the benefits of the European Geostationary Navigation Overlay Service (EGNOS) in areas of Eastern Europe where it is not yet available, such as Poland, Romania, Ukraine, Moldova and Russia, and to prepare the civil aviation authorities and air navigation service providers for future use of the system.

GMV’s magicSBAS solution.

In the context of this project, after the tests conducted in Spain, the maiden flights have been successfully carried out in Moldova, using the equipment and tools developed by GMV. The Moldova demonstrations have given pilots and service providers a clear idea of the potential benefits of EGNOS and the flying procedures of the near future, GMV said.

Four flights had previously been conducted in Spain in November, December and February. The satisfactory results of these flights then paved the way for the demonstrations in Moldova.

The magicLPV system, developed under this project, enables LPV approaches (localizer performance with vertical guidance) to be carried out using the signal generated by the magicSBAS application. This test environment allows any region of the world to analyze the air-navigation benefits to be obtained with deployment of a Space Based Augmentation System (SBAS). This signal is read by Internet and transmitted by radio frequency in the vicinity of the airport, allowing LPV approaches to be made in places where SBAS is either completely unavailable or available only on a very limited basis.

Eight flights in all were carried out in various Moldovan airports, including Chișinău International Airport. Test results were highly satisfactory, demonstrating the simplicity of equipment configuration and operation, and the performance of the magicSBAS signal, GMV said.

“These trials are an important milestone for GMV, for the project and, fundamentally, for the use of EGNOS in the countries of Eastern Europe in the near future,” said Miguel Romay, executive director of GNSS–Aerospace.

GMV will continue with these demonstrations in other countries of Eastern Europe. The next trip in two weeks will be to Romania, where new flights are expected to be just as successful.

Update: The launch window for the liftoff has been adjusted slightly to  21:38-21:56 UTC.

The United Launch Alliance (ULA) Atlas 5 rocket’s rollout to the pad  took place Tuesday. Weather forecasters have predicted an 80
percent chance of favorable conditions for launch.

Updates on the mission and live video coverage of the launch is available.

Live video will also be available here and on this satellite feed (for those of you still with backyard dishes): SES 2, Transp. 21, C-band, 87° West

ULA is also posting to Facebook and tweeting to Twitter at twitter.com/ulalaunch; look for the #GPSIIF-4 hashtag.

The next GPS satellite launch is scheduled for May 15 with the launch window extending from 21:39 to 21:58 UTC. An Atlas 5 rocket will be used to place the satellite, GPS IIF-4, into orbit from Cape Canaveral Air Force Station.

This is the first time in almost 28 years that an Atlas rocket will be used to launch a GPS satellite. All of the prototype or Block I satellites were orbited with Atlas rockets. Since then, Delta rockets have been used exclusively for GPS launches. The IIF satellites are being launched with a mixture of Atlas and Delta rockets.

The IIF-4 satellite, also known as SVN66, will operate as PRN27. SVN66/PRN27 will eventually occupy the C-2 slot, replacing SVN33/PRN03, a Block IIA satellite launched in 1996. Reportedly, SVN66/PRN27 will go through an extended period of testing following launch, and is not expected to be set healthy until August. SVN33 will become a reserve or backup satellite.

Ground Stations: ER = Eastern Range; BOSS = Call sign of New Hampshire Station, New Boston Air Force Station, New Hampshire; LION = call sign of Telemetry & Command Station, Royal Air Force Oakhanger, Hampshire, U.K.; Diego Garcia = Diego Garcia Station (call sign REEF), British Indian Ocean Territory; Guam = Guam Tracking Station (call sign GUAM), Dededo, Guam.
TDRS: Tracking and Data Relay Satellite
MES1: Centaur first main engine start
MECO1: Centaur first main engine cutoff
MES2: Centaur second main engine start
MECO2: Centaur second main engine cutoff
At spacecraft separation, the GPS satellite’s orbit will be circular with a height of 11,047 nautical miles or 20,459 kilometers and an inclination of 55 degrees.

(Courtesy of SpaceFlight Now) This is the 45th Launch Support Squadron crew patch for the GPS 2F-4 mission, which is Boeing’s Space Vehicle (SV) #5. Each SV is a named for a navigation star and its constellation. SV-5 is named Vega, with constellation Lyra. On the patch, they are the large star and constellation in the background of space. The United Launch Alliance Atlas 5 rocket is shown lifting the satellite from the Eastern Launch Site at Cape Canaveral Air Force Station. The Squadron mascot is a gator, and a lyra is a Greek harp. SSgt Thomas Hogan drew a “Toga-Gator” and Lt Ken Stuart did the patch design.

“A billionth of a second equals a nanosecond, a time interval far beyond our own human capacity of appreciation,” explains Marco Falcone, ESA’s Galileo System Manager.

The prediction error for the offset between Galileo System Time and UTC, expressed in nanoseconds. The UTC value available to the user via Galileo is expected to be accurate within 26 nanoseconds, but in spring 2013 it has been even better, with a prediction error in the last two months of less than five nanoseconds.

“A single lightning flash across the sky during a thunderstorm lasts about ten milliseconds, which is already 10 000 000 nanoseconds. But for high-tech applications, as well as navigation services, nanosecond accuracy is essential.”

The replacement for Greenwich Mean Time, UTC is part of all our daily lives: it is the timing used for Internet, banking and aviation standards as well as precise scientific experiments, maintained by the Paris-based Bureau International de Poids et Mesures (BIPM).

The BIPM computes UTC based on inputs from collections of atomic clocks maintained by institutions around the world, including ESA’s ESTEC technical centre in Noordwijk, the Netherlands.

‘Galileo time’ is derived independently of UTC but is being kept close to it, with a precise ‘offset’ between the two values being calculated continuously and then disseminated through Galileo’s navigation message.

Galileo, like all other satellite navigation systems, is based on the highly precise measurement of time. A receiver on the ground pinpoints its position by calculating how long signals from satellites in orbit take to reach it.

Matching the receiver and satellite clocks then multiplying the time taken by the speed of light gives the range between user and satellite, allowing the receiver to fix its own location relative to four or more satellites.

“Each navigation system has its internal reference system time used to synchronise all system clocks and maintain overall coherence,” adds Marco.

Galileo’s navigation message embedded in its signals include precise timings based on Galileo System Time, kept close to global time standard UTC with a precise offset given, accurate to at least 26 nanoseconds.

INRIM has been supporting ESA’s Galileo development since the early phases of the project. More recently INRIM has overseen the creation of a ‘Time Validation Facility’ for Galileo in collaboration with five other European time-measurement institutions: the Physikalisch Technische Bundesanstalt in Germany, the National Physics Laboratory in the UK, the Systeme de References Temps Espace/Observatoire de Paris in France, the Real Instituto y Observatorio de la Armada in Spain and Observatoire Royale de Belgique.

Galileo’s Ground Control Segment (GCS) in the Fucino Control Centre in Italy oversees Galileo navigation services and satellite payload operations.

Each day, the most precise European clocks and national time scales are compared to GST and the offset compared to UTC is estimated and provided to the Galileo Control Centre. This offset is then uploaded to the Galileo satellites for transmission in the navigation message available to users.

As explained by Patrizia Tavella from INRIM, “The UTC value available to the user via Galileo is expected to be accurate within 26 nanoseconds, but in the last two months it was even better, with a prediction error in the last two months of less than five nanoseconds.”