Türkiye is no stranger to earthquakes. In February 2023, a devastating 7.8-magnitude earthquake struck near the Türkiye-Syria border, followed by another nearly as strong.
Six Turkish universities have launched a real-time geodetic monitoring network to track earthquake-related ground deformation across Thrace and the Southern Marmara region, reports Hürriyet Daily News.
TR-TRAK-GNSS will monitor seismic and tectonic activity using 28 GNSS stations. The system is designed to evolve into a major scientific and early-warning infrastructure capable of detecting tectonic deformation in real time and identifying structural movements in buildings across cities and university campuses.
Once fully deployed, the network will form a continuous monitoring ring encircling Thrace and Southern Marmara.
The project will be financed through each participating university’s Scientific Research Projects resources, with institutions covering the installation costs of GNSS stations within their own areas of responsibility.
The Institute of Navigation’s (ION) Satellite Division presented several annual awards Sept. 25 during the ION GNSS+ Virtual Conference.
Morton Honored with Kepler Award
Y. Jade Morton received the Johannes Kepler Award for advances in scientific and navigation receiver technology, automated data collection, robust carrier phase tracking, remote sensing, and profound impact as an educator and author.
Morton is the director of the Colorado Center for Astrodynamics Research at the University of Colorado, Boulder ,where she mentors students, faculty, staff and an ever-expanding international network of collaborators throughout the world. She is a prolific author with more than 270 publications. She was awarded her Ph.D. in Electrical Engineering at Pennsylvania State University. She has also authored articles for GPS World.
Receiver Technology Pioneer. Morton has made pioneering contributions to the advancement of GNSS receiver technology and utilization of these enhanced capabilities for scientific discovery. Her work brings together scientific rigor with state-of-the-art engineering innovations to simultaneously improve PNT, while revealing remarkable new applications for GNSS.
Morton’s lab-developed event-driven GNSS data acquisition systems (EDAS), designed to capture severe space weather and ionosphere disturbances of GNSS signals, which could not be handled by existing GNSS monitoring receivers. Her lab designed and built remotely-configurable, multi-GNSS, multi-band, SDR hardware using off-the-shelf components; and developed software including machine-learning algorithms for automatic event detection to trigger raw data recording during these events.
Network established. Her lab deployed these receivers worldwide. The network has enabled unprecedented studies and forecasting of ionosphere/space weather phenomena, detection of satellite oscillator anomalies, and development of advanced GNSS receivers for navigation and remote sensing under challenging conditions.
Morton’s group has made groundbreaking advances in GNSS carrier-phase processing and established theoretical performance bounds. Her group developed optimal carrier tracking loop architectures and implementations, and successfully applied the techniques to processing signals experiencing strong ionospheric scintillation for ionosphere and space weather research; radio-occultation signals traversing moist lower troposphere for weather and climate modeling; weak coherent reflected signals from ocean, land, and sea ice for precision altimetry applications; and navigation in urban canyons and on high dynamic platforms.
Morton is an expert on space weather and ionosphere monitoring. Her research findings range from climatology and morphology of ionospheric plasma irregularities to spatial, temporal and frequency domain characteristics; cause-effect relationships between solar-geomagnetic activities and GNSS signal disturbances; and radio wave propagation theory and simulation. The studies, based on data from her GNSS networks, magnetometers, radar and satellite-based measurements, cover the globe from the arctic to the equator and span an entire solar cycle.
Volunteer service. Morton has served numerous organizations with thousands of hours of volunteer service including organizing each of the ION’s large technical conferences and leading over 10 student teams participating in ION’s autonomous lawn mower and snowplow competitions, is credited as one of the co-organizing founders of the ION’s Pacific PNT conference, has served as the ION Satellite Division Chair and is the current ION President. Dr. Morton is a past recipient of the IEEE Kershner Award and the ION’s Burka and Thurlow Awards. She is a Fellow of the ION, RIN and the IEEE.
The Johannes Kepler Award recognizes and honors an individual for sustained and significant contributions to the development of satellite navigation. It is the highest honor bestowed by the ION’s Satellite Division.
Kimia Shamaei Honored with Parkinson Award
ION’s Satellite Division presented Kimia Shamaei with its Bradford W. Parkinson Award Sept. 25 for her thesis, “Exploiting Cellular Signals for Navigation: 4G to 5G.”
The Bradford W. Parkinson Award is awarded annually to an outstanding graduate student in GNSS. The award, which honors Dr. Parkinson for his leadership in establishing both the U.S. Global Positioning System and the Satellite Division of the ION, includes a personalized plaque and a $2,500 honorarium.
Any ION member who is a graduate student completing a degree program with an emphasis in GNSS technology, applications, or policy is eligible for the award. ION thanks the altruistic experts who served on this year’s selection committee.
Trimble’s RTX-based correction services now support the Galileo constellation. As a true five-constellation technology that uses GPS, GLONASS, BeiDou, QZSS and now Galileo satellites, Trimble RTX delivers improved real-time positioning performance to its users worldwide.
With accessibility to the Galileo constellation, users now have visibility to more satellites, which can be advantageous for extreme latitudinal positions or in environments where line-of-sight may be limited.
Surveyors, farmers, mapping and GIS professionals now have a more versatile and robust correction solution wherever they may work, even in the most challenging terrain locales.
Benefits of adding Galileo to Trimble RTX correction services includes:
Increasing the number of in-view satellites, improving the accuracy and reliability of corrections
Improving positioning integrity using observations from additional satellites to better mitigate errors
Operating at higher cut-off angles, delivering better performance in urban canyons and other less than optimal environments
Minimizing multipath and interference through the addition of available satellite signals
“Trimble is continually investing in its correction service technology to remain at the forefront of the industry,” said Mark Richter, marketing director for Trimble’s Networks and Services business. “Our focus is to ensure that the latest GNSS developments are leveraged to continue to deliver productivity improvements for our customers across the globe.”
Septentrio has received a contract to supply 35 high-precision GNSS receivers to the Jet Propulsion Laboratory (JPL) for use in the NASA Global GNSS network (GGN).
The NASA GGN is one of the world’s largest global GNSS tracking networks with nearly a hundred reference receivers deployed worldwide and is a participant in the International GNSS Service (IGS). The GGN is also the core tracking network of JPL’s Global Differential GPS (GDGPS) System, a highly available and reliable service providing mission-critical position, navigation and timing data, as well as environmental monitoring for industry and government operations.
The Septentrio PolaRx5 GNSS receiver.
Under the contract, Septentrio will supply 35 of its new-generation PolaRx5 GNSS receivers, including 25 reference stations and 10 timing instruments. Deliveries began in August and will be completed in September.
The PolaRx5 incorporates Septentrio’s most advanced multi-frequency GNSS engine, which tracks all major satellite signals including GPS, GLONASS, Galileo and BeiDou, as well as the regional QZSS and IRNSS satellite systems. It provides measurement quality and interference mitigation, and operates on less than two Watts when receiving GPS and GLONASS satellite signals.
“This major contract with JPL — a widely recognized industry leader in GPS and GNSS technology — is an important validation of Septentrio’s position as the number one preferred supplier of highly accurate GNSS receivers for scientific applications, and recognition of the superior performance of our next-generation GNSS receivers,” said Neil Vancans, vice president of Septentrio Americas.
A lot of talk is being made about UAVs these days and how this technology is going to revolutionize many industries, with surveying being one of the biggest users.
I won’t deny the impact this new tool is going to have on our profession (as written in my last column). But I don’t think it will compare to the use of GNSS technology and how it modernized measuring methods for the surveyor.
I’m often asked by young surveyors what I think is the biggest improvement experienced by the surveying profession. Ironically, I asked that same question to my teachers when I was a new survey technician. My mentors will talk of the electronic distance meter, the theodolite or the total station. (Some old timers even told me the best improvement was the gammon reel for their plumb bob or the reel for a steel “chain”!)
While these were good advancements, for me the biggest improvement was the introduction of GPS into surveying, followed by the advancement to real-time network capability. Now, coupled with modern communication methods of radio or cellular transmission to permanent base stations, the GNSS rover has become one of the most valuable tools in the surveyor’s toolbox.
To understand the importance of GNSS technology and its use by the surveying community, first take a look at the history of the profession and method/devices used for measuring. Land surveyors have been measuring boundaries of parcels for centuries, dating back to Egyptian times and workers known as “rope stretchers.” Their use of rope with knots tied at specific intervals was the measuring stick of the time period.
As centuries passed and measuring units were developed, surveyors used these dimensional tools for measuring and describing land parcels. By the time the early settlers of America began traveling westward, surveyors were using a 66-foot-long Gunter’s chain made with 100 links, each almost eight inches long. Over time the links would stretch until the surveyor’s measurements were not accurate for land surveys.
By the early 1900s, tapes made from low-expansion steel became more widely used and much more accurate for surveying. The early 1960s brought new technology with measurement systems using laser light beams with the ability to travel several miles with sufficient accuracy.
A total station.
The electronic distance meter (EDM) allowed the surveyor to cover longer distances in much less time than the conventional method of the steel tape, leading to more productive field time. This technology was further refined to be installed inside of traditional theodolites to create the modern total station instrument — still used today for basic measuring of angles and distance. Almost all surveying projects can be completed using a total station, but the invention of a remotely available measuring device would be a welcome tool in the surveyor’s toolbox.
Enter the 1980s and the adaptation of the military’s satellite measuring system for civilian use. While early users and developers needed a Ph.D. in mathematics to configure its use, GPS measurement revolutionized long-distance measurement for the surveying profession. Static GPS measurement took many hours of data collection and even longer processing time, but with terrific results and with tremendous accuracy.
Further refinements with hardware and software configurations brought more affordable and user-friendly systems that gave surveying community another resource for accurate measurement. While the use of real-time kinematicc (RTK) expanded greatly in the late 1990s and 2000s, the big difference in the past 10+ years has been the introduction of real-time networks and permanent base stations. This advancement helps by eliminating the need for a base receiver and radio with an amplified repeater, and thus another employee guarding the idle base station equipment.
Depending on the surveyor’s location, real-time networks are readily available by paid subscription or through publicly funded transportation department. These systems are very reliable and don’t require a six-figure investment in equipment.
All survey data-collection methods, no matter the measuring procedure used and positional accuracy required for the project, needs to follow a strict quality-control procedure for verification of its content and position. The old adage “Measure twice, cut once” works well here, too, so let’s discuss what is involved with good measuring procedures.
Measuring procedures
Prior to any field measurements are taken, it is good practice to verify satellite availability during your planned measuring period. The U.S. GPS currently consists of 31 active and healthy units orbiting the planet and crisscrossing the sky 24/7. The geometry created by radio signals received from these satellites constantly vary in size and strength. By using mission-planning software, the user can accurately predict the best times of the day to collect positional locations with the highest accuracy and repeatability. Low numbers of satellites or strength of constellational geometry can lead to inaccurate locations and incorrect measurements between points.
The introduction and allowance of other satellite systems into our data collection system (GLONASS, Galileo, BeiDou, IRNSS) will enhance the availability and strength of constellation geometry throughout the data-collection process.
Another potential problem for GNSS data collection is solar storms, sunspots and other radio interruptions. Most manufacturers will notify the user of major atmospheric radiation events, but check the NOAA Space Weather Prediction Center (SWPC) website for updates on potential events. The key here is to plan your field collection prior to execution, in order to reduce errors in measurement or even interruptions to completing the work in a timely manner.
Survey results are only as good as the measurements, and following strict guidelines is very important. When using survey-grade GNSS equipment in a real-time function, many items need to be monitored while collecting data to ensure good quality positions. Here are items as listed by the National Geodetic Survey (NGS) in the “User Guidelines for Single Base Real-Time GNSS Positioning” manual on the NGS website:
Accuracy versus precision
Accuracy is how your collected data compares to the defined standard.
Precision is how often the solution is repeated.
Achieving both provides necessary confidence in field measurements.
Redundancy
The ability to collect similar measurements at different times, satellite constellation geometry and atmospheric conditions.
Multipath
Minimizing opportunities for measurement to be affected by reflected or misdirected signals.
Position dilution of precision (PDOP)
Higher readings usually achieved when measuring during periods of weak satellite constellation geometry.
Root-mean-square (RMS)
Statistical measurement of precision notifying the user of the positional quality of the measurement based upon quality of satellite signals.
Site localizations/calibrations
Basing the strength of survey network on the location of the base station and the accuracy of the monument it is located upon.
Typically used when real-time network connectivity is not achievable.
Latency
The delay of the received satellite signal data and correction information at the base, sent to the rover for computing correction values.
Signal-to-noise ratio (S/N)
Ratio in which burdening noise is measured versus the actual signal from the satellite.
Float and fixed solutions
Floating solutions occur when precision for survey-grade measurements is not met due to noise, lack of satellites, weak satellite geometry and latency.
Elevation mask
This setting is a filter to eliminate signals from satellites below the user-defined angle, thus eliminating opportunities for weak constellation geometry and noise interference.
Geoid model
Correction model used to improve vertical measurement with GNSS data collection by incorporating previously determined elevations across a wide area.
While all of these components are necessary for quality data collection, one of the most critical steps is horizontal and vertical verification on published or previously established control points or monuments. By checking into a known point before every data-collection session, you can eliminate errors in rod/antenna height and/or coordinate system setup. Checking a known point can also help determine if the correction signal is providing accurate information, either from the RTK base station or as part of a subscription service via cellphone or radio. It will also help discover poor PDOP or RMS due to weak satellite configurations. Also, if the rover unit takes longer than usual to initialize, a potential data-collection issue may occur to bad conditions.
The biggest complaint I get (and see) is field crews not checking the accuracy of the GNSS unit during the course of a survey. Hopping out of the vehicle, firing up the data collector, and taking a measurement multiple times without redundant measurements or verifying existing control points/monuments is a recipe for disaster.
Here are my keys to successful data collection with GNSS technology:
Keep the equipment is good working order: batteries charged, receivers and collectors in travel cases when not in use, poles kept in safe places and regularly checked for plumb.
Utilize a checklist for project startup.
a. Horizontal coordinate system to be used.
b. Vertical datum to be used.
c. List of multiple published or previously established control points for datum verification.
Once receiver has a fixed solution, verify horizontal and vertical position on known point.
Minimize loss of fixed solution times, recheck when establishing new fixed positions.
If possible, recheck main control points at various time throughout the day to establish redundancy.
Reverify at the end of the session and at the end of the day.
While GNSS has greatly decreased field time for covering large areas quickly, it must still be used correctly in order to provide accurate positional locations. The accuracy of these positions are what the measurements of the surveyor relies upon, and they must meet a high standard of confidence. Our profession prides itself on being called upon as the “expert measurer,” so our methods of measurement must be up to those standards.
While it took a little time to get the cost-effectiveness, reliability and user friendliness to a level of affordability for the surveyor, GNSS has become one of the best tools in our toolboxes. GNSS has revolutionized modern surveying, and I, for one, appreciate its ability to help me offer my services as an expert measurer.
By Martti Kirkko-Jaakkola, Stefan Söderholm, Salomon Honkala, Hannu Koivula, Sonja Nyberg, and Heidi Kuusniemi, Finnish Geospatial Research Institute (FGI), National Land Survey of Finland
Our real-time kinematic (RTK) implementation, the Public Precise Positioning (P3-Service) project, has achieved horizontal positioning accuracy of 0.5 meters using relatively inexpensive equipment: a commercial off-the-shelf (COTS) low-cost GNSS receiver. The project used FinnRef, the Finnish national GNSS network.
With inter-station baselines on the order of 200 kilometers, FinnRef is relatively sparse in comparison with commercial RTK networks. We used FinnRef as the RTK base station, either in single-base or network RTK mode. Although FinnRef’s main purpose is to maintain the national coordinate system, it is also capable of delivering DGNSS and network RTK data over the NTRIP protocol.
Transport Applications. Horizontal position accuracy of 0.5 meters or better, achieved for more than 90 percent of the time with small, low-cost devices, could be useful in various applications, particularly in intelligent transportation systems.
Current consumer-grade GNSS solutions routinely offer a positioning accuracy in the order of 5 meters, and satellite-based augmentation systems (SBAS) such as WAAS and EGNOS can improve the accuracy to the order of 1 meter. However, this is not adequate for all use cases; in particular, intelligent transportation systems (ITS) require better positioning performance. For instance, a horizontal accuracy of 0.5 meters is needed to reliably identify the lane in which a vehicle is driving. Maintaining inventory of machines, road signs and other infrastructure would also benefit from sub-meter accuracy.
Sub-meter or even sub-decimeter positioning accuracies can be attained with a relatively good reliability in real time if a dual-frequency GNSS receiver and a physical or virtual base station are available. However, such receivers and virtual base station services are currently too expensive to gain popularity in the mass market. Recently, precise point positioning (PPP) has demonstrated that comparable accuracies can be attained without a base station using real-time precise correction data, but its drawback is a long convergence time. In contrast, differential methods utilizing raw base-station observations, such as RTK, converge much faster.
Horizontal position estimation results from a low-cost COTS receiver (right); the green triangle marks the reference position solution.
Network RTK Test. Network RTK performance was tested in a static scenario with the closest physical base station 63 kilometers from the rover receiver. Network corrections were delivered in the PRS representation, and data were logged for 20 minutes at a rate of 1 Hz. The plot above shows the resulting horizontal position errors. The dashed red circle with a radius of 0.5 meters centered at the reference location (green triangle) contains 90.4 percent of the position estimates.
For a full account of the experiments and results described here, see the paper “Low-Cost Precise Posioning Using a National GNSS Network,” presented at ION GNSS+ 2015.
