Oregon Department of Transportation workers use DT Research’s GNSS rugged tablets. (Photo: DT Research).
The Oregon Department of Transportation (ODOT) has expanded its use of DT Research GNSS rugged tablets to all 15 of its construction management offices across the state, and also use the tablets for biology, geology, roadway and wetland projects.
DT Research worked closely with ODOT to design purpose-built rugged tablets that empower state workers to easily collect and transmit geospatial measurements in the field using GNSS real-time kinematic (RTK) technologies.
“DT Research’s GNSS rugged tablets have enabled us to bring high-accuracy geospatial measurements to workers across the Department of Transportation, which has literally changed the way we work,” said Chris Pucci, construction automation surveyor at ODOT. “The tablets have enabled us to save time, reduce costs and improve the accuracy of projects through ‘digital-as constructed’ measurements and real time data capture.”
The tablets have a dual-frequency GNSS module built in, which provides stand-alone sub-meter accuracy to centimeter-level accuracy with RTK from GPS, GLONASS and Galileo satellites.
The tablets are compatible with existing survey and GIS software for mapping applications and provide an advanced workflow for data capture, accurate positioning and data transmitting.
“We now have essentially created one-person survey crews because the DT Research tablets are so much easier to use than a tape measure and paper to accurately calculate and record measurements during complex construction projects,” Pucci said. “Using the tablets saves us an average of $2,000 for every survey-grade measurement job that does not require a full survey crew.”
“In addition, the tablets have provided us with a contract verification system by having highly accurate digital-as-constructed measurements that are delivered immediately and stored forever, which saves the state time and money by avoiding independent re-measurement checks due to billing discrepancies at the end of a project,” added Pucci.
The DT Research GNSS tablets can store up to 1 Terabyte of data for field data collecting. Users can avoid down time with a high-capacity hot-swappable battery pack, which delivers 60 or 90 watts for up to 15 hours of continuous mobile communications. The units include Long Range Class 1 Bluetooth, which powers wireless connectivity up to 1,000 feet and 4G mobile broadband.
“The simplicity of how the DT Research tablets work is amazing,” Pucci said. “Unlike complex professional survey equipment, the DT Research tablets are a Windows-based mobile device with a user interface that is familiar to workers. In just two hours, I can easily train state workers with diverse skill sets to measure quantity, linear features and volumes for a variety of projects — and they are ready to go.”
The tablets run on Microsoft Windows 7 Professional or Windows 10 IoT Enterprise and are high performance devices with an Intel 6th or 8th Generation Core i5 or i7 processor. The rugged tablet is designed for outdoor use with a brilliant LED-backlight, 800 nits sunlight-readable screen and capacitive touch.
“We have found the DT Research tablets to be incredibility easy to manage and highly durable — we just turn them on and they work,” said Pucci. “In the three years that we have used the tablets, we have had very few technical support questions and they hold up well in different weather conditions. There isn’t a comparable product on the market at the price point.”
The DT Research tablets are military-grade durable devices, yet lightweight, offering the versatility to be used in field-to-office settings. For use in harsh environments, the tablet is fully ruggedized to meet the highest durability standards with an IP65 rating, MIL-STD-810G for vibration and shock resistance and MIL-STD-461F for EMI and EMC tolerance.
For use in a variety of environments, the tablets are complemented by many accessories including: external antennas, pole mount cradles, detachable keyboards, battery charging kits and digital pens.
Spire Global, a space-to-cloud analytics company, is now using Galileo to offer GNSS radio occultation (GNSS-RO) products for the weather community. Radio occultation is the process of using satellites to measure how GNSS signals are refracted by the Earth’s atmosphere.
Two of Spire’s nanosatellites are the first to use Galileo signals to measure GNSS-RO profiles, a service now available to Spire’s global user base as a new tier of data for advanced weather prediction. The satellites launched on Nov. 29, 2018, from Sriharikota, India.
The satellites are part of the collaborative European Space Agency ARTES Pioneer Space-as-a-Service program, which aims to prove the value of using nanosatellites for space-based GNSS-RO.
With Galileo, Spire’s weather observation satellites can harvest approximately 25 percent of the total GNSS-RO profiles available from the existing GNSS satellite constellations in orbit today.
Spire operates 72 nanosatellites — also known as “cubesats” — and more than 30 ground stations throughout the world. The nanosatellites are developed, assembled and tested at Spire’s production facility in Glasgow, Scotland.
A kite-blown science expedition to the interior of Antarctica has made the most southerly positioning fixes yet made with Europe’s Galileo satellite navigation system.
The Inuit WindSled is a multi-part sledge the size of a lorry, complete with mounted tents and solar power panels, pulled through the ice using a mammoth 150 sq. m. diameter kite. (Photo: Inuit WindSled via ESA)
Their measurements not only confirm Galileo performance at extremely high latitudes, but also offer knowledge of space weather events overhead. In particular they offer insights into the ionosphere — the electrically active upper layer of Earth’s atmosphere — above the southern continent, and the performance of Galileo software to correct ionospheric interference.
The four-person expedition left Russia’s Novolazarevskaya Base on 12 December last year. For more than 40 days they made their way to Dome Fuji, a 3810-meter-high ice dome in Eastern Antarctica — one of the coldest places on Earth. After reaching the high point on 21 January, they are now back at the Russian base.
The Inuit WindSled is a multi-part sledge the size of a lorry, complete with mounted tents and solar power panels, pulled through the ice using a mammoth 150 sq. m kite. (Graphic: ESA)
The “Antarctica Unexplored 2018-2019″ expedition, mounted by Spain’s Asociación Polar Trineo de Viento, is employing a unique zero-emission vehicle specially designed for polar exploration. The Inuit WindSled is a multi-part sledge the size of a lorry, complete with mounted tents and solar power panels, pulled through the ice using a mammoth 150 sq. m kite.
The Windsled’s inventor, Ramón Larramendi, is also the expedition leader. “This marks the first time we’ve climbed the Fuji Dome in a vehicle driven by the wind — everyone who reached there before relied on motorised vehicles. So this is also the first time we’ve traveled more than 2,400 km with more than 2,000 kg of cargo using a vehicle that does not pollute the Antarctic continent,” Larramendi said.
“We are also doing this in collaboration with ESA, among other scientific institutions, which is very important because it allows us to demonstrate this polar eco-vehicle has excellent possibilities for enabling science in the interior of the Antarctica continent,” Larramendi said.
The four-person “Antarctica Unexplored 2018-2019” expedition left Russia’s Novolazarevskaya Base on Dec. 12, 2018. For more than 40 days they made their way to Dome Fuji, a 3810-meter-high ice dome in Eastern Antarctica — one of the coldest places on Earth. (Graphic: ESA)
The expedition carries a total of 10 scientific experiments from different research institutions, covering fields such as climate change, meteorology and astrobiology. ESA’s involvement with the expedition is the Galileo Experimentation and Scientific Test in Antarctica (GESTA) project.
GESTA involves regular positioning fixes being made over the course of the expedition for all satellite navigation constellations in all kinds of weather and geomagnetic conditions encountered. ESA provided the satnav receiver, with GMV in Spain contributing an advanced signal recorder for data analysis.
One of the important aspects of the study is the monitoring of the ionosphere in such high latitudes during low solar activity. Ionospheric interference can degrade satellite navigation performance, and its incidence is linked to solar activity.
The expedition team with their Inuit WindSled at the high point of Dome Fuji. Note the ESA logo on the left tent of the WindSled. (Photo: Inuit WindSled via ESA)
GESTA is overseen by ESA’s Galileo Navigation Science Office, led by Javier Ventura-Traveset. “We are very pleased with this pilot scientific experience, having been able to collect Galileo measurements all over the expedition trip as planned,” said Ventura-Traveset. “The expedition reached latitudes near 80 degrees south, to our knowledge the most southerly latitude measurements ever-performed in-situ with Galileo in its current near-complete constellation status.
“We have also collected data from all other global satellite navigation systems and all available different frequencies, which will allow us also to assess multi-constellation solutions and compare their performance on these conditions. The expedition team kept in continuous contact via satellite with our office, allowing us to plan their activity, asking, for example, for dedicated data collections during space weather relevant events.”
“Once the expedition data are delivered, we will be able to assess Galileo positioning, navigation and timing capabilities at polar latitudes and how they are influenced by space weather events during low solar activity,” said Manuel Castillo, system engineer at the Galileo Navigation Science Office. “In particular, we will analyze if the occurrence of coronal holes is correlated with observed ionospheric interference. Coronal holes are open areas in the Sun’s outer layer, the corona, that allow the solar wind to leave the Sun and reach Earth, triggering moderate geomagnetic storms.
“At this moment in the 11-year solar cycle, with the Sun close to minimum activity, full-scale solar storms are not frequent, but the ongoing communication between the WindSled team and the Galileo Navigation Support Office allowed us to coordinate measurement times during the three minor geomagnetic storms the expedition experienced during the trip.”
A coronal hole in the Sun, observed by NASA’s Solar Dynamics Observatory on Jan. 5, 2019. (Photo: NASA)
The coronal holes triggering these geomagnetic storms were monitored, meanwhile, by Sun-watching missions such as NASA’s Solar Dynamic Observatory, the NASA-ESA SOHO and ESA’s Proba-2.
ESA’s Galileo Navigation Science Office is based in European Space Astronomy Centre, ESAC, near Madrid. It was set up in 2016 as a joint initiative between ESA’s Science and Navigation Directorates, coordinating scientific opportunities through interaction with the scientific community and the independent GNSS Science Advisory Committee.
The 2019 Munich Satellite Navigation Summit, which will take place March 25-27 in Munich, Germany, will offer a number of educational sessions to attendees.
One of the sessions will key in on the future use of the Galileo public regulated service (PRS). According to show organizers, this session will discuss the deployment of the Galileo ground- and space-segment — including the PRS relevant components — which will reach full operational capability in the next years. The session will also cover PRS-receiver developments and PRS testing.
Other sessions offered by the conference will include legal aspects on selected topics in the field of GNSS; augmented reality meets high-accuracy positioning; GNSS program updates; satellite and terrestrial navigation trends; and more.
According to organizers, the Summit is part of the efforts of the Bavarian government and the cluster on aerospace and satellite navigation to stimulate applications and services in this high-tech field.
The event, which is organized by the European Space Agency and ETH Zürich, will take place Sept. 4-6 in Zürich, Switzerland.
The event will bring together members of the European scientific community and their international partners involved in the use of GNSS — specifically Galileo — in their research. In addition, attendees will discuss opportunities where GNSS satellites can be used for scientific purposes.
According to event organizers, the colloquium will address five major areas of research, including:
Scientific applications in meteorology, geodesy, geodynamics, geophysics, space physics, oceanography, land surface and ecosystem studies, using either direct or reflected signals, differential measurements, phase measurements, radio occultation measurements, using receivers placed on the ground, in airplanes or on satellites;
Scientific developments in physics with a potential impact on future GNSS, particularly in testing fundamental laws of physics;
Aspects of metrology such as reference frames, on board and ground clocks, precise orbit determination and time and frequency transfer;
Scientific aspects of satellite navigation, positioning and its applications, such as signal propagation, tropospheric and ionospheric corrections, multi-constellation aspects, hybridisation with additional sensors and integrated navigation, precise positioning;
Transversal topics of interest to a wide number of scientific fields including collection of GNSS big data and GNSS scientific data archives; internet of things positioning for science; scientific payloads in GNSS satellites; novel disruptive technologies for science; the use of cubesats, HAPS, UAVs and autonomous vehicles for GNSS science; software receivers and low-cost SDR platforms; GNSS for space users and applications; and the topic of GNSS science and education.
The conference will be organized as a series of plenary talks, parallel half-day sessions and poster presentations throughout the duration of the event, event organizers add.
The document contains the Galileo E6-B and E6-C codes specifications, including primary and secondary codes and their assignment to satellites, which is necessary for manufacturers who are developing Galileo E6-B/C enabled receivers.
The technical note represents the first step for these forthcoming Galileo services: high-accuracy service (HAS) and commercial authentication service (CAS) on E6-B/C signal.
By William Roberts, Joshua Critchley-Marrows, Marco Fortunato, Maria Ivanovici, Nottingham scientific Ltd., Karel Callewaert, Thiago Tavares, VVA Brussels, Laurent Arzel and Axelle Pomies, Telespazio France
The FLAMINGO initiative is developing the infrastructure, solutions and services to enable use of accurate, precise GNSS in the mass-market, operating predominantly in an urban environment. Whilst mass-market receivers are yet to achieve accuracies below one meter for standard positioning, the introduction of Android raw GNSS measurements and the Broadcom dual frequency chipset present such an opportunity.
FLAMINGO will enable high-accuracy positioning and navigation information on devices such as smartphones and internet of things (IoT) devices by producing a service delivering accuracies of 50 cm (at 95 percent) and better, employing multi-constellation, PPP and RTK mechanisms, power consumption optimisation techniques.
Whereas the Galileo High Accuracy Service targets 10-cm precision for professional users, FLAMINGO targets 50-cm precision for consumers. With accuracies of a few decimetres, a range of improved and new applications in diverse market sectors are introduced, including, but are not limited to, mapping and GIS, autonomous vehicles, augmented reality environments, location-based gaming and people tracking.
To obtain such high accuracies with mass market devices, FLAMINGO must overcome several challenges which are technical, operational and environmental. This includes the hardware capabilities of most mass-market devices, where components such as antennas and processors are prioritised for other purposes. We demonstrate that, despite these challenges, FLAMINGO has the potential to meet the accuracy required. Tests with the current smartphones that provide access to multi-constellation raw measurements (the dual-frequency Xiaomi Mi 8 and single-frequency Samsung S8 and Huawei P10) demonstrate significant improvements to the PVT solution when processing using both RTK and PPP techniques. Check out more information here.
The European Space Agency (ESA) has received approval from the Galileo Security Accreditation Board to upgrade the global infrastructure running Europe’s Galileo satellite navigation system.
According to ESA, the resulting migration, set to start in February 2019, will incorporate new elements into the world-spanning system and boost the robustness of Galileo services delivered from the 26 satellites in orbit.
The system qualification campaign, which was run by the ESA Galileo project team in coordination with the WP1x system support team led by Thales Alenia Space in Italy, took more than a year to execute. It included more than 150 system tests — summing up to a total of 409 tests runs across Europe — in the various Galileo operational centers.
Galileo’s global ground segment. (Photo: ESA)
According to ESA, a major driver of this latest update was the growth of the Galileo constellation, which increased by 12 satellites through a trio of Ariane 5 launches in the last three years to become Europe’s largest.
The updated ground system incorporates a sixth telemetry, tracking and control station in Papeete, used to oversee Galileo satellite platforms, as well as an expansion of the number of antennas at the sites of uplink stations at Kourou in French Guiana, Reunion Island in the Indian Ocean and Noumea in French Polynesia.
In addition, receivers have been added to the Galileo sensor stations to ensure full redundancy.
“This marks the first update for Galileo’s operational infrastructure since it entered service,” said Edward Breeuwer, ESA Galileo system test and verification manager. “Galileo Initial Services began in December 2016, then last year we passed control of the system to our partner organization, the European Global Navigation Satellite System Agency, or GSA.
“This, therefore, marks a major step, but migration to the upgraded system should in principle be entirely transparent to Galileo users. We achieve this by taking advantage of the redundant elements of the Galileo system, taking them offline to update them while their operational counterparts continue to run.”
Mountainous areas present special problems for surveyors, overcome by the expanded availability of multi-GNSS. (Photo: Trimble)
Today’s GNSS satellites transmit on three or more carrier frequencies. The quality of the data in these signals from GPS, BeiDou, Galileo, GLONASS and QZSS reveals the expected measurement precisions. This article explores the noise of the range residual and ionospheric residual to indicate the oncoming capabilities.
Today, four GNSSs transmit various codes on various carrier frequencies: the USA’s GPS, Russia’s GLONASS, Europe’s Galileo and China’s BeiDou. Most of the carrier phase and pseudorange data are available using civilian GNSS receivers. Improvements in signal quality as well as reliability of the satellites are foreseen through the generations, as well as the introduction of new signals, such as L1C, L2C, L5 carrier and codes, and M-codes, on top of the existing L1-C/A code and the P(Y) code on both L1 and L2. Improvements are also seen in boosting the transmitting power.
This article investigates the use of two approaches to analyze the relative noise in the various carrier phase and pseudorange observable for GPS, BeiDou, Galileo, GLONASS and Japan’s Quasi-Zenith Satellite System (QZSS) augmentation. Two approaches analyze the relative noise in the observables: the range residual and the ionospheric residual. Both techniques can also be used to detect cycle slips.
Range Residual
UAV survey operations benefit from multi-GNSS receivers. (Photo: Septentrio)
The range residual is simply the change from one epoch to the next in the difference in the range calculated using the pseudorange and the range calculated by the carrier phase on a specific frequency. The pseudorange values are scaled using the wavelength to an equivalent range in units of the carrier’s cycles rather than meters. Equation 1 illustrates the range residual between the pseudorange ρ on a specific carrier frequency and the carrier phase observable φ, using the wavelength λ of the carrier to scale the pseudorange. The values of these observables are compared between adjacent epochs.
RR = (p/λ) – φ (1)
Two adjacent epochs are used, as then the integer ambiguity value, as well as the ionospheric and tropospheric errors, and satellite and receiver clock errors are the same, or negligibly different at such small (<1 s) epoch intervals. Therefore, these are all canceled out, and the resulting value is the measurement receiver and observable noise. The pseudorange observable will be significantly noisier than the carrier phase observable, therefore this method is a good way to calculate the measurement noise for the pseudoranges.
Ionospheric Residual
Surveyors work the Berezitovy mine in the North Amur region of Russia. (Photo: Javad GNSS)
If the carrier waves traveled only through a vacuum, then a phase observation from a specific satellite to a specific GNSS receiver could be scaled and converted to an equivalent phase measurement on another frequency using the frequencies of the carrier waves. However, as the signal passes through the ionosphere, systematic errors that are frequency dependent are introduced, so it is not possible to directly convert from one carrier phase value to another for a specific range measurement. The error is known as the ionospheric residual, and this will change slowly over time as the satellite passes overhead and the ionosphere being passed through changes, and also as the ionosphere slowly changes its characteristics over time, mainly due to the sun’s activities.
Equation 2 shows the calculation, using L1 and L2 carrier phase readings and corresponding frequencies, used to calculate the ionospheric residual. Again, the difference in the ionospheric residual values between adjacent epochs is used, as in the same way as the range residual values, external noise sources are eliminated.
(2)
Results
The results presented here are a subset of a much larger set. Figure 1 illustrates the range residuals for L1 and L2 as well as the L1L2 ionospheric residual for PRN32 (Block IIA satellite).
Figure 1. L1 range residual (left) L2 range residual (center) and L1L2 ionospheric residual (right) for GPS PRN32 (Block IIA) satellite. (Charts: Authors)
Figure 2 illustrates the L1 and L5 range residuals and the L2 (C-code) L5 ionospheric residual for PRN01 (Block IIF satellite).Both figures’ data are for the complete passing of the satellites from horizon over and back down again.The data for PRN32 is all that exists in the datafile, as this satellite only transmits L1 CA code and P(Y) code, as well as L2 P(Y) code, and corresponding carrier values.
Figure 2. L1 range residual (left) L5 range residual (center) and L2 (C code) L5 ionospheric residual (right) for GPS PRN01 (Block IIF) satellite. (Charts: Authors)
PRN01 is a block IIF satellite, and data for L1 CA code, L2 P(Y) code as well as L2 C-code, L5 code, and corresponding carrier phase values are recorded in the datafile.The block IIF satellites can result in four range residual values and five ionospheric residual combinations.Figure 2 only illustrates three of these combinations.The data were obtained from the Curtin University GNSS repository on Sept. 1, 2015, gathered at a 1-Hz epoch interval; 29,908 epoch of data were gathered for PRN32, and 26,073 epochs for PRN01.
It can be seen from these figures that the L1 range residuals are similar in characteristics for both PRN01 and PRN32.The values are noisy at the start and the end of the time series, indicating that the CA code is more prone to noise at low elevations.Comparing these to the L2 (PRN32) and L5 (PRN01) range residuals, we can see that both the L2 and L5 range residuals are not as prone to low elevation noise. Also, the two L2 and L5 range residuals are visually similar in characteristcs.By comparing the L1L2 and L2L5 ionospheric residuals (Figure 1, right, and Figure 2, right), we can see that the L1L2 combination is slightly noisier than the L2L5, in particular at low elevation angles.
If we compare BeiDou ionospheric residual results, we can see the comparison of noise on the three ionospheric residual combinations, B1B2, B1B3 and B2B3, as well as the results from the three types of satellite orbits, ie MEO, IGSO and GEO. Figure 3 illustrates the ionospheric residual results for PRN07 (IGSO) for the three frequency combinations, from data gathered on a static pillar located on top of the University of Nottingham Ningbo China’s Science and Engineering Building.
Figure 3. Ionospheric residual results for BeiDou PRN07 (IGSO) for combinations B1B2 (left), B1B3 (center), B2B3 (right). (Chart: Authors)
Figure 4 illustrates the ionospheric residual results for PRN01 (GEO) for the three frequency combinations.
Figure 4. Ionospheric residual results for BeiDou PRN01 (GEO) for combinations B1B2 (left), B1B3 (center), B2B3 (right). (Chart: Authors)
Figure 5 illustrates the ionospheric residual results for PRN12 (MEO) for the three frequency combinations. Here it can be seen that the B2B3 combination is generally less noisy than the B1B2 and B1B3. In addition to this, it can be seen that when the MEO and IGSO satellites are at lower elevation angles, the observables also become noisier. The GEO satellites have a constant elevation angle, and do not experience this phenomenon.
Figure 5. Ionospheric residual results for BeiDou PRN12 (MEO) for combinations B1B2 (left), B1B3 (center), B2B3 (right). (Charts: Authors)
Detailed Results
The data, gathered on a single GNSS receiver located at the University of Curtin’s GNSS research center, was downloaded in BINEX format and converted into RINEX 3.02 format using RTKLIB software. Software was developed by the authors in Matlab in order to interrogate the data files and implement the range residual and ionospheric residual algorithms. RINEX 3.02 format was chosen due to its compatibility with multi-GNSS and multi-frequencies.
Industrial UAV applications such as construction draw benefits from multi-GNSS receivers’ capabilities. (Photo: Skycatch, Swift Navigation)
Results are presented for both ionospheric residual and range residual results for various GNSS. These results have been calculated with varying elevation mask angles, ranging from 0° to 55° at 5° intervals. The RMS values of the resulting ionospheric residuals and range residuals were calculated and plotted against the respective elevation mask angle for each satellite and frequency combinations. This illustrates the influence of the elevation mask angle used on the results.
Typically, tens of thousands of epochs of data were used for every plotted point in the following figures. Further to this, not only are the results for the various frequencies and frequency combinations for the various GNSS illustrated, but also the various satellite types, MEO, GEO and IGSO, and various satellite Blocks for GNSS. GPS Block IIA (PRN04 and PRN32), Block IIR (PRN14), Block IIR-M (PRN31) and Block IIF (PRN01, PRN26, PRN25) data were all analyzed. Thus, the comparison of the various frequencies within each satellite system are illustrated, as well as the variations by comparing the various satellite constellation types and the various generations of GPS satellites.
Surveying accuracy is critical to roadway construction. (Photo: Leica Geosystems)
The BeiDou data illustrated are MEO (C12, C14, C11), IGSO (C09, C10, C07) and GEO (C01, C02). The data used were gathered on Sept. 1, 2015, in order to include GPS Block IIA satellites (PRN04 and PRN32). PRN32 was retired in June 2016, and PRN04 was taken out of active service in November 2015, but the satellite was reactivated in March 2018, this time broadcasting PRN18.
Figure 6 illustrates RMS of the range residual results for GPS (a), BeiDou (b), Galileo (c), GLONASS (d) and QZSS (e) respectively. These figures have been drawn so that the y-axis ranges are the same for each, hence illustrating the relative values.
Figure 6A illustrates the range residual results for GPS. It can be seen that the L1 CA code results are the noisiest, with PRN14 being the noisiest, followed by PRN31, PRN26, PRN01, PRN04, PRN25 and PRN32. It can also be seen with these results that lower elevation angle mask increases the noise level. Both the L2 and L5 code results are less noisy.
Figure 6A. RMS range residual results for GPS. (Chart: Authors)
Looking at the detail, the L5 code results is less noisy than the L2 and affected less than the L1 results by the changes in elevation mask angles used. Interestingly enough, the data file includes both the L2 P(Y) code and L2C code results. L2C only exists on the Block IIR-M and Block IIF satellites. The L2C code results are generally noisier than the L2 P(Y) code.
Figure 6B illustrates the results for the range residuals for the BeiDou satellites. Here it can be seen that the B1 code is affected more by low elevation mask angles than B2 and B3. It can also be seen that both the geostationary satellites’ B1 results stand out, with satellite C02 being noisier than C01. The B2 and B3 values for both these GEO satellites are bunched up with the majority of the other results towards the middle of the figure. The pairs of B2 and B3 results for the GEO satellites are close to each other in values, and the pairs of B2 and B3 results for the other satellites are also close to each other.
Figure 6B. RMS range residual results for BeiDou. (Chart: Authors)
It can also be seen that the range residual results for BeiDou are generally less noisy than than GPS, in units of cycles.
Similarly, for Galileo, Figure 6C, the E1 results are worst, and affected more by low elevation masks. Again, generally the Galileo results are seen to be improved over GPS. The GLONASS results, Figure 6D, illustrate that the L1C results are generally noisier, and then the L1P, followed by L2C and L2P. PRN09 is also consistently generally noisier than PRN10. Finally, Figure 6E illustrates the results for QZSS. Again, L1C is the noisiest and affected most by low elevation mask angles.
Figure 6C. RMS range residual results for Galileo. (Chart: Authors)Figure 6D. RMS range residual results for GLONASS. (Chart: Authors)Figure 6E. RMS range residual results for QZSS. (Chart: Authors)
Figure 7 illustrates the ionspheric residual results for the same satellites as Figure 6. This time, however, the resulting ionospheric residual values are calculated using pairs of data from the same satellite on different carrier frequencies. The range residual results compare the code and carrier from specific satellites and frequencies.
Figure 7(a) shows that the ionospheric residual results are affected by low elevation masks, and that the L1L2CW (L1 CA code and L2 P(Y) code available on all the satellites) combinations are the noisiest, followed by L2L5WX (L2 P(Y) code and L5 code available on Block IIF satellites, PRN 26, PRN01, PRN25), followed by L1L2CX (L1 CA code and L2 C code available on Block IIF and Block IIR-M satellites, PRN31, PRN26, PRN01 and PRN25), followed by L1L5CX (L1 CA code and L5 code, Block IIF satellites, PRN01, PRN25, PRN26) and finally the least noisy were the L2L5XX results (L2 C code and L5 code available on Block IIF satellites, PRN26, PRN25 and PRN01).
Figure 7A. Ionospheric residual results for GPS. (Chart: Authors)
Figure 7(b) illustrates the BeiDou ionospheric residual plots, illustrating that satellite C14 is much noisier for all three combinations of B1B3, BB1B2 and B2B3 in that order. The B1B2 combinations for the satellites are generally the noisiest, and then the B1B3 and B2B3 combinations are intertwined. The Galileo results again illustrate that the E1 combinations are generally noisier, and again we see the effect of low elevation angle masks, Figure 7(c). Generally, however, the Galileo results are less noisy than GPS, as are the BeiDou results.
Figure 7B. Ionospheric residual results for BeiDou. (Chart: Authors)Figure 7C. Ionospheric residual results for Galileo. (Chart: Authors)
The GLONASS results are again generally the noisiest, and again PRN09 is noisier than PRN10, with the L1P combinations being noisier, Figure 7(d). Figure 7(e) for QZSS shows that there are generally two groups of results. The upper set consists of L1L2ZX, L1L5ZX, L1L2XX, L1L5XX, L1L6ZX and L1L6XX from highest to lowest noise respectively. The lower, less noisy, group consists of L1L2CX, L1L5CX, L2L5XX, L2L6XX, L1L6CX and L5L6XX from highest to lowest noise respectively. Further details about the various codes and carrier values can be found in the RINEX 3.02 manual produced by the IGS.
Figure 7D. Ionospheric residual results for GLONASS. (Chart: Authors)Figure 7E. Ionospheric residual results for QZSS.(Chart: Authors)
Conclusions
A surveyor checks an urban construction project. (Photo: Topcon)
These preliminary results illustrate that there are differences in the noise values for various GNSS, frequencies as well as satellite generations and orbit types. It can be seen that generally L1, B1 and E1 have noisier results, and are affected moreso by low elevation mask data, and hence multipath. It can also be seen that newer generations of satellites do indeed produce better quality data.
Some specific satellites produce lower quality data such as GLONASS PRN09 and BeiDou C14. This could be due to multipath produced at the satellite.
Today roughly 100 GNSS transmit data, and typically users can gather data from 30 to 50 at any time. Positioning requires nowhere near this number of satellites, therefore decisions are needed as to which satellites and which data to use in a positioning solution. Our findings imply that our approach could be used in such decision-making in GNSS processing software, helping the software to choose the optimum satellites to draw from in a positioning solution.
Acknowledgments
This work described in this article was first presented at the FIG 2018 conference held in Istanbul, Turkey. The authors acknowledge the use of data supplied from the Curtin University GNSS Centre.
Manufacturers
The GNSS receiver used is a Trimble NET R9, and the antenna is a Trimble TRM 59800.00 SCIS choke ring antenna. A ComNav K508 GNSS receiver supplied some of the BeiDou results.
GETHIN WYN ROBERTS is an associate professor at Fróðskaparsetur, the University of the Faroe Islands. He is past Chairman of the FIG’s Commission 6, Engineering Surveys, and previously held posts at the University of Nottingham both in the UK and in China. He holds a Ph.D. in engineering surveying and geodesy from the University of Nottingham.
CRAIG M. HANCOCK is an associate professor in Geodesy and Surveying Engineering and the head of the Department of Civil Engineering at the University of Nottingham, Ningbo, China as well as the head of the Geospatial and Geohazards Research Group. He holds a PhD from the University of Newcastle Upon Tyne.
XU TANG is a research fellow at the University of Nottingham, Ningbo, China. He holds a PhD from Nanjing University.
Elsewhere in this (January) issue you’ll find the hard facts — basic, but hard — concerning the inaugural launch of the long-awaited GPS III constellation. On pages 10 and 12, with some seasoned leavening between, on page 11.
This column instead waxes briefly on the phenomenon of time, and humankind’s struggle to dominate it, to subject the fourth dimension to its own will.
For GPS III has been, yes, long awaited, long debated, long victim to multiple delays of many colors and causes, scrutable and inscrutable, of technological challenges and institutional barriers, and of that base determinant, money. The Government Accounting Office has issued its fair and due share of reports pointing alarmed fingers at constellation gaps and fulfillment shortfalls and the trials of OCX, the ground control system without which GPS III satellites may some day, soon or not-soon, be capable of broadcasting powerful new signals from space, yet not able to do so because of lagging accomplishment on Earth.
It’s often said that GPS is a victim of its own success, that older satellites living beyond their forecast lifetimes have allowed the Air Force to economize by not replenishing when unnecessary. There’s wisdom in this, of course.
Were my friend Don Jewell still with us, he would be justifiably proud of the Air Force for launching this new golden era of the gold standard in positioning — yet he would have seethed for years over the continued pushes to the right.
This reminds me a good deal of the drama and occasional comedy in the rise of Galileo, observed from afar. Next month I’ll give a talk at the European Space Agency, provisionally titled “An Outside History of Galileo,” the bemused viewpoint of one who only heard and interpreted the news, but did not participate in its forming.
For such complex endeavors do not happen easily or speedily or exactly as planned by mere mortals. Nor should they. Despite much gnashing of teeth, no one — in the civil sphere at least — has suffered unduly from the longish delays in either satnav system’s modernization. Perhaps a few lives could have been saved in the military, or greater strategic advantage gained, with the new capabilities that III will offer warfighters, had same been available on schedule, say, four to six years ago. But even this is mere conjecture.
There is a rhythm and a flow to life, and we are part of it. You can hurry neither sundown nor sunrise. Things happen in their own due course.
When full GPS III capabilities arrive — I don’t believe 2023 — then it will still be in good time. In its own best time, actually, to be here.
Calendar pages allows seem to fly by quickly, and 2018 was no different. While many of the items discussed in last year’s review continued to be topics of advancement, there are several new sources of technology, data collection and potential issues for surveyors going into the new year.
Let’s look back at the stories that affected the surveyor and their use of GNSS technology in 2018.
FCC broadband accuracy
The race across America to provide better broadband coverage hit a snag late in 2018 when critics of the Federal Communications Commission (FCC) voiced their displeasure with the accuracy of maps produced to depict the coverage of broadband access.
These critics are pressuring the FCC to verify internet coverage and speed of data availability in rural areas as reported by the broadband companies.
The FCC unveiled a new broadband map in February 2018. (Image: FCC)
These broadband companies are only required to report on the advertised availability and data speeds and not the actual coverage/speed of the installed networks. Critics of the FCC have found that information used from the broadband providers overstates the available speeds and number of internet service providers, thus allowing the FCC to produce mapping of broadband that is not correct.
Because of this incorrect reporting, it is estimated that almost 40 percent of rural America doesn’t have access to broadband data with no formal plan of rectifying this situation. The FCC has stated that they will investigate these coverage maps in order to determine if monies distributed to broadband providers were not used in accordance with the promised delivery of coverage and data speed.
Why does this matter to surveyors? As previously discussed in past columns, the reliance on the real-time network capability of GNSS is one of the biggest time and production savers for the surveyor and for those working in rural America is no exception.
Not just in small towns but out in the open where large parcels are being surveyed for many different reasons, including pipelines, wind and solar installations and title conveyances. By having broadband available use by surveyors, these tasks can be accomplished with shorter timeframes and less steps to keep critical data in compliance with established coordinate systems.
While this bill received lots of attention because of the FAA implications, the portion of the bill concentrating on geospatial oversight will have a lasting effect on the governance and development of the national mapping industry.
For many years, the ever-developing amount and sources of geospatial data has been growing within several different agencies of the United States government. This bill was established to help streamline the efforts and availability of geospatial data by assigning specific agencies to oversee the development and introduction of new technologies.
The biggest takeaway from this bill will be the reduction of agencies working on concurrent data sets for public and private use and therefore streamlining the opportunities to introduce newly acquired information into critical programs, (such as FEMA floodplain mapping, GAO asset management, etc.).
Part of the reason I wish to highlight this bill was the efforts of the National Society of Professional Surveyors (NSPS) to keep the state professional licensing laws intact, the use of private sector businesses for providing surveying services, and to keep quality-based selection (QBS) as the primary tool for awarding contracts for procurement services.
Because of the actions and reasoning by NSPS, the authors of the bill withdrew the language that would allow “low bid” opportunities within these contract awards. This influence by NSPS is a prime example of how a profession can influence legislation through our democratic process.
Galileo implementation, Beidou installation, GPS Block III launches
SpaceX’s Falcon 9 rocket orbited the first GPS III satellite on Dec. 23, 2018. (Photo: SpaceX)
In November 2018, the FCC opened a new chapter in GNSS observation by approving a waiver to allow GNSS receivers to utilize Galileo transmissions for location determination without a specific FCC license. Traditionally, the FCC would require licensing of public, receive-only GNSS equipment used with any foreign-based systems but worked with several US agencies to create a waiver to allow faster implementation to use the Galileo signals.
It should also be noted that the Chinese government has been rapidly building the latest stage of their own GNSS constellation, the BeiDou system. The United States and China have been promoting cooperation to allow each side to better understand the current workings of GPS and BeiDou, (GPS-BeiDou Statement). China is currently completing its third phase of the navigation system that potentially will surpass the United States GPS constellation in data availability and accuracy, (See GPS World“Directions 2019: BeiDou accelerates global deployment,” December 2018).
Not to be outdone, the U.S. has begun its implementation of their next wave of satellites, the GPS III containing the latest technology, the L1C civil signal, with improved accuracy and anti-jamming programming. On Dec. 23, the SpaceX Falcon 9 rocket delivered the GPS III SV01 into its intended orbit (SpaceX Launch) with more launches scheduled for additional satellite vehicles in 2019.
These efforts to increase satellite coverage and accuracy will only improve the use of GNSS receivers by surveyors. While I look forward to software and receiver upgrades to take advantage of the newer birds, we still need a backup plan in case of international conflicts and a reduction/discontinuation of GNSS service.
GPS and terrestrial backup
The Frank LoBiondo U.S. Coast Guard Authorization Act of 2018, which also included the National Timing Security and Resilience Act, was signed into law on Dec. 4 and directs the Secretary of Transportation to establish a terrestrial back system for the U.S. satellite navigation system within a two-year period (see “GPS to get terrestrial backup system”).
The bill lays out specific conditions for the backup plan:
terrestrial
wireless
synchronized to UTC
difficult to disrupt
able to penetrate underground and inside buildings
capable of deployment to remote locations
expandable to provide position, navigation and timing (PNT), and
able to work in concert with similar systems such as eLoran.
However, this bill did not provide any funding for the creation of this system but now allows the introduction of appropriations in future bills and acts. As I have written in past columns (see “The day GPS went away,” September 2017), it won’t be a matter of if but when something happens to our current GNSS capabilities and we need to develop this backup plan yesterday.
Dual-band GNSS cellphones as the new norm
My last submission featured the latest in chipset for cellphones and utilizing dual-frequency GNSS signal reception. Xiaomi, based in Beijing, China, introduced the Mi 8 phone with a dual-frequency GNSS chip in the Spring of 2018 to rave reviews.
This chip frequency reception (E1/L1+E5/L5) is targeted to embrace the Galileo and GPS constellations for increased accuracies (within a decimeter) well beyond the current norm for smartphones (typically 1-3 meters +/-).
Since then, Xiaomi has released the Mi Mix 3 and Huawei has released the Mate 20, Mate 20 Pro and Mate 20 X, all with dual-frequency chipsets. However, all of these phones are not available in the U.S., and the security issues with Huawei has been well documented (CNBC Report, February 2018).
The reason I still bring these up for the surveyor is because soon we will have dual-frequency capability on the phone in our pockets here in the U.S. Such phones can greatly increase efficiencies, especially when used during reconnaissance efforts. I believe many more phone manufacturers will begin to incorporate dual-frequency chips in their future models to increase location accuracies for the users and take advantage of upcoming network enhancements (see GPS World“Dual-frequency GNSS smartphone hits the market,” June 2018.)
Surveyors vs. technology disruptors
The Mi 8 smartphone offers dual-frequency capability. (Image: Xiaomi)
One of the biggest stories in the surveying world made national headlines after a start-up “GEO-spatial” consultant created by retired bankers was sued by the Mississippi Board of Licensure for Professional Engineer and Surveyors for having “engaged, and continues to engage in the practice of surveying while not licensed by the Board.” (Madison County, Mississippi, Chancery Court.) While the initial suit remained under the national radar, the countersuit by the consultant and subsequent articles in national websites brought the situation to the front page.
The issue at hand is the creation of “plats” combining a legal description for a parcel with a high-resolution photo (captured by various means, including UAV) and depicting said legal description on the photo for use by banks and other financial institutions for risk evaluation. Their argument is that they have “First Amendment rights” to provide public information (the legal description) on a recent aerial photograph in order to provide an exhibit for lenders to review and make loan decisions. Banks are now paying much less in fees to this company for an exhibit instead of a Plat of Survey provided by a licensed surveyor, yet the exhibit provides no assurance (or certification) to its validity and/or any metadata for the represented information.
The subsequent articles by both Bloomberg and Ars Technica writers liken the situation to Airbnb versus hotels and Uber/Lyft versus taxi drivers as a new “disruption in technology” brings forth change to previously licensed professions. In fact, the author of the Bloomberg article stated, “the clients are sophisticated, and they’re not complaining.”
Using this mentality, we could apply it to any licensed profession and allow services normally regulated by laws to be administered by non-professionals, as long as the client “is sophisticated and not complaining.” This means anyone can provide accounting, medical, dental or even law services if the client is satisfied. As previously published here, (see GPS World“Accuracy, precision and boundary retracement in surveying” July 2017), a boundary survey is not simply a mathematical figure from a legal description. It takes a trained person to know how to properly relate a legal description to a physical parcel and professional licensing provides that assurance (and protection) to the public.
This situation falls squarely in the GNSS wheelhouse for surveyors, especially as technology advances and accuracies become smaller with progress, (i.e. GPS Block III, BeiDuo, Galileo, etc.) and the ability to measure with higher positional accuracy, (i.e. Xiaomi Mi 8 and other to follow).
The surveying profession has joked for years that when these technologies do come forward, many unlicensed “professionals” will come forward with their measuring devices (phones) and locate property lines as part of their service.
But for now, it isn’t just the physical location by GNSS measurement we should worry about; it is the high-resolution photo software, GIS data sources and those folks enterprising enough to put all this information together. The surveying profession will need to ramp up its message to public to help better define what the licensed surveyor provides versus the “we can do it much cheaper and faster” stories. More often than not, you get what you pay for.
Data collection advancements
Emlid Reach RS with iPad. (Photo: Tim Burch)
While 2018 didn’t see any revolutionary changes to GNSS data collection, several small advances are noteworthy. Besides the previously mentioned dual-frequency cellphones, we are also seeing more integration with the cellphones themselves as data collectors in conjunction with stand-alone GNSS receivers (see GPS World“University research uses smartphones for precision GNSS,” September 2018).
Several of the major survey equipment manufacturers are joining a group of small GNSS start-ups by introducing single- and dual-frequency receivers to work with both Android- and iOS-based phones and tablets for more cost-effective positional solutions.
Another trend that is becoming very popular is the use of post-processing kinematic (PPK) solutions with many of the newest models of multi-rotor and fixed wing UAVs. The early (and expensive) trend of aerial vehicles produced by the major surveying equipment manufacturers insisted on installation of a dual-frequency RTK receiver in order to provide a more robust control system for the orthometric photo process. Because there is still a need to combine the still photos from the UAV flight via various “stitching” software, the need (and expense) of RTK within the receiver, while a nice feature, has become overkill for most aerial needs. However, there are times and applications when a fixed-RTK location could be useful, especially during emergency situations when needing to utilize the UAV for live streaming purposes.
The last big trend to gain popularity comes from Propeller, a young tech company from Australia that provides both a control point product and data reduction/reporting service. Their revolutionary ground control point (GCP) target, the Aeropoint, is becoming a very popular item for UAV pilots worldwide. These 24-inch (61-CM) square foam targets contain a single-frequency GNSS receiver that collects RINEX data while performing your UAV flight. Spread these targets around your site, setup and perform your survey, then download the target data to the Propeller app on your phone/tablet. The app automatically uploads the data to the company’s site and processes the geographical location for each target into your chosen coordinate system. It truly is that simple and the Propeller folks have made it easy to use. Their online software, Propeller Platform, is also available for photo/data processing and site analysis/visualization/volume computations. They, too, are now teaming with DJI to offer PPK solutions combining Aeropoint data along with Phantom 4 RTK photo data in a convenient, streamlined process.
For 2018, our firm (SPACECO Inc) expanded our UAV program in several ways to take advantage of these trends. First, we been using the Emlid Reach RS single-frequency GNSS receiver utilizing a Bluetooth connection to an iOS-based tablet to GCP’s for our UAV program. The receiver’s low cost and ease of use with an RTN network has been a pleasant change from typical surveying equipment. We also use Propeller’s Aeropoints in locations where the RTN coverage is not readily available. For sites that are substantial (typically 300 acres+), we often send our data to the Propeller Platform for photo stitching and data reduction to take advantage of their computing power.
WingtraOne. (Photo: Brian Kravets, SPACECO Inc.)
Lastly, we wanted to expand our fleet of quad-rotor UAV’s to include a fixed wing model for larger sites. A visit with the Wingtra crew at InterGeo 2017 in Berlin convinced me that a vertical take-off and land (VTOL) model would be a great addition, so we took delivery of our WingtraOne this past summer. The ease of use and amount of project space the Wingtra can cover was already great but we’ve added the PPK module to reduce the amount of GCP’s necessary, especially in inaccessible areas. All these additions to our survey department (carefully vetted and purchased; no freebies from any of the manufacturers!) have provided new ways to expand our services to our clients and allows us the opportunity to enjoy what we do along the way. It is my pleasure to report from personal experience that these trends are solid and will continue to increase our abilities and productivity for days to come.
What’s next for 2019?
Some of the items I see gaining traction in 2019 will include additional sensors for UAV’s (LiDAR, hyperspectral, infrared), continued improvement in cost effectiveness of laser scanners and LiDAR, increased interest in SLAM (simultaneous localization and mapping) technology and, of course, more geolocation services tied into autonomous vehicles/delivery. Will 2019 be the year Amazon drops my packages by UAV at my front door? As fast as these technologies are developing, I wouldn’t bet against it.
The U.S. Federal Communications Commission (FCC) granted in part the European Commission’s request for a waiver of the commission’s rules so that non-federal devices in the United States may access specific Galileo signals. While private users were free to use the European GNSS, with this ruling entities such as telecommunications companies can now also use Galileo.
With today’s action, consumers and industry in the United States will now be permitted to access the E1 and E5 Galileo signals to augment GPS.
Since the debut of the first consumer handheld GPS device in 1989, consumers and industry in the United States have relied on the U.S. GPS to support satellite-based positioning, navigation, and timing (PNT) services that are integral to everyday applications ranging from driving directions to precision farming.
The order, approved Nov. 15, finds that Galileo is uniquely situated as a foreign GNSS system with respect to the U.S. GPS, since the two systems are interoperable and radiofrequency compatible pursuant to the 2004 European Union/United States Galileo-GPS Agreement.
Specifically, the order permits access to two of the Galileo system’s satellite signals — the E1 signal that is transmitted in the 1559-1591 MHz portion of the 1559-1610 MHz Radionavigation-Satellite Service (RNSS) frequency band, and the E5 signal that is transmitted in the 1164-1219 MHz portion of the 1164-1215 MHz and 1215-1240 MHz RNSS bands. These are the same RNSS bands in which the U.S. GPS satellite signals operate.
The order does not grant access to the Galileo E6 signal, which is transmitted over the 1260-1300 MHz frequency band, since this band is not allocated for RNSS in the United States or used by the U.S. GPS to provide PNT services.
The commission noted that granting access to the Galileo E6 signal could constrain U.S. spectrum management in the future in spectrum above 1300 MHz, where potential allocation changes are under consideration.
