“Is the GNSS community failing to exploit the potential of chip-scale atomic clocks (CSAC)?”
John Fischer
“Yes! And there are several CSAC suppliers, each with varying accuracies, power consumptions, and price points. These atomic clocks are no longer exotic scientific instruments but rather commercialized, proven devices that can be mounted on a circuit card at a reasonable cost. They offer extended holdover time in the absence of GNSS and help with spoofing detection by verifying the incoming signal. They provide exact frequency recovery on power-up (re-trace) for power saving modes. Defense, telecom, financial transactions, and autonomous navigation for cars and drones are all applications that can be made more resilient by these clocks.”
“Atomic clocks, including CSAC, are frequently used in GNSS timing applications, for example to keep accurate time during GNSS outages or to assist in identifying spoofing attacks targeting the time component. On the other hand, the long-term stability of atomic clocks is not particularly relevant in navigation applications where time is not the main output, and the additional cost, power consumption and size of CSAC are not justified.”
“Indeed. After the DARPA-NIST initiative and subsequent commercialization, affordable, accurate and stable chip-scale oscillators can be easily integrated into circuit boards providing additional measurements to PNT systems to improve positional vertical accuracy, as well as reliability and integrity. For example, in high-end mobile mapping systems operating in complex urban scenarios, their use helps detect GNSS outliers at a relatively negligible additional cost.”
“When Galileo was just an idea, its EU proponents used the argument of “political, economic, social and technological sovereignty.” Should countries such as Brazil build their own GNSS constellations?”
Ismael Colomina
“When, almost 20 years ago, I was in Brazil giving talks about the future of Galileo and promoting its combined use with GPS, I was often asked the logical question as the EU Galileo sovereignty arguments were known. It is not for us Europeans to answer that question for other countries or oppose their plans. However, while being aware of the defense aspects of GNSS, we may ask ourselves whether an international cooperative approach could avoid a somewhat unjustified future proliferation of GNSS constellations.”
“GPS enables continuous access, free of fees and political encumbrances. A decision by any nation to bear the cost of creating a separate GNSS should be justified by realistic requirements for security or coverage that cannot be satisfied by GPS. Japan, South Korea and India are models for additional GNSS services driven by regional needs. For any new system, compatibility with other GNSS, as well as life-cycle costs, are the primary factors to consider.”
“When Galileo was just an idea, the U.S. military’s GPS was the only viable global constellation. GLONASS was a rusting cold-war relic and BeiDou was in an embryonic stage. The U.S. military’s official policy was that any civilian use was not guaranteed and could be interrupted anytime. Therefore, no nation outside of the United States could depend on GPS and maintain its independent interests. However, today, any country could reasonably maintain its sovereignty by ensuring interoperability with all four — betting that at least one of those constellations would always be available to them. They don’t need their own system.”
“Those are always nice-sounding words when trying to justify a monumentally huge expense. However, is there an actual need to justify that expense? Can the expense and burden of perpetual system operation and maintenance, along with technological innovation to keep pace with other systems and user requirements, be guaranteed over the long term? For the users, GPS can be seen as the gift that keeps on giving, whereas to the operators it is the gift that keeps on costing. So, do Brazil, or other nations, have the commercial or social need, technological foundation, economic resources and political will to initiate a new system and sustain it over the long term? Providing a GNSS constellation is not for the faint of heart or those of short-term vision.
What would be required for the United States to develop and deploy a GPS high-accuracy service analogous to Galileo’s HAS?
Ismael Colomina
“Galileo HAS is a particular implementation of a PPP-RTK service. U.S. companies are already providing similar fee-based services that are even more accurate than HAS. Therefore, there is no big technical challenge for the United States to provide a GPS HAS. Actually, the European Union already provides a HAS for GPS. It is more a question of strategy for GPS policy makers: which user segment to service with a HAS-like augmentation? What about other services analogous to Galileo’s OSNMA and the upcoming CAS [commercial authentication service] for resiliency purposes? In short, a HAS-like service would just require including it in the U.S. GNSS evolution roadmap.”
— Ismael Colomina GeoNumerics
John Fischer
“The challenge is probably more political than technical. The U.S. government usually refrains from competing with commercial services. The prevailing attitude in the United States is that the private sector is more efficient than the public sector. Maybe the most practical approach is for the government to provide the authentication mechanism and open access to the data required, then allow the private sector to offer services. There isn’t a pressing need for high-accuracy GPS for transportation — it needs resiliency/reliability. However, precision agriculture needs it, so maybe sponsorship from the Department of Agriculture would be more effective than from the Department of Transportation.”
— John Fischer Orolia
Mitch Narins
“When I saw this question, my first impression (as a systems engineer) was to ask ‘For whom? For what applications? For which services?’ (Positioning? Navigating? Time/frequency?) Many have concentrated on accuracy, competing in a GNSS Olympics to see who can achieve ‘the best’ position accuracy and precision (repeatability). Finally, (thanks to Logan Scott) integrity is being pushed beyond just SBAS and GBAS, and real civil authentication of signals is being pursued. I can promise nanometers/nanoseconds if I don’t have to prove it’s true. While we finally understand the need for zero trust, we must still address loss of service by establishing real complementary PNT.”
How is the completion of Galileo and BeiDou affecting the development of autonomous vehicles?
Ismael Colomina, chief scientist, Geonumerics
“GNSS has had a limited impact on the development of AVs because their developers regard it as insufficiently accurate, reliable, and ubiquitous. Only a minority of them are aware of the benefits that the new/modernized constellations bring. More and improved signals and new services— both commercial and public—such as Galileo’s HAS, NMA and CAS will enable and complement visual, lidar and radar sensors for SAE levels of automation 2 and higher and for ASIL D safety levels.” Ismael Colomina GeoNumerics
Ellen Hall, Spirent Federal System
“Safety is critical to the implementation of AVs and this safety relies upon PNT accuracy, availability and robustness. These three requirements all benefit from constellation diversification in terms of multiple signals, frequencies, satellites, and constellation providers. In addition to the four civilian signals available on three frequencies from the GPS constellation, signals from Galileo and BeiDou provide suitably equipped receivers with extra satellites, signals and ground segment diversity.” Ellen Hall Spirent Federal Systems
Brad Parkinson
“The economic potential of self-driving vehicles is the major driver for their development. Can they be made affordable, safe, dependable, and useful? More operational GNSS constellations may help resolve these issues favorably, but GNSS progress should not significantly influence the large number of developers. My favorite such application is long-haul trucking, which may have some very favorable profit and safety benefits.” Bradford W. Parkinson Stanford Center for Position, Navigation and Time
How have improvements in mapping data-collection advanced other PNT technologies?
Tony Agresta
“Real-time positioning, navigation and timing (PNT) benefit from high-resolution aerial maps captured and published on a consistent basis. With sub 3-inch aerial photographs streamed through custom applications or instantly accessible solutions, governments and commercial use cases apply these maps for emergency 9-1-1 dispatch, routing guidance, and new information applications to inform citizens.” Tony Agresta
Nearmap
Ismael Colomina
“In principle, PNT shall be based on linear/angular motion sensors. However, since the origins of aerial triangulation down to contemporaneous hybrid multi-sensor systems, mapping and motion sensors have cooperated in PNT tasks. Current visual- and lidar-odometry are brilliant examples thereof.” Ismael Colomina
GeoNumerics
Members of the EAB
Tony Agresta Nearmap
Miguel Amor Hexagon Positioning Intelligence
Thibault Bonnevie SBG Systems
Alison Brown NAVSYS Corporation
Ismael Colomina GeoNumerics
Clem Driscoll C.J. Driscoll & Associates
John Fischer Orolia
Ellen Hall Spirent Federal Systems
Jules McNeff Overlook Systems Technologies, Inc.
Terry Moore University of Nottingham
Bradford W. Parkinson Stanford Center for Position, Navigation and Time
Kinematic Ground Control point for UAV photogrammetry: A dynamic duo of UAV and mobile van combine to deliver the accuracy of conventional methods with only 2+2 ground control points at the ends of the corridor.
By Ismael Colomina, Pere Molina and Roberto da Silva Ruy
A Brazilian and a Spanish company, ENGEMAP and GeoNumerics respectively, have finalized the accuracy evaluation of a mission conducted with the latter’s mapKITE technology on a Brazilian motorway in 2018.
The goal of the evaluation was to confirm the advantages of the mapKITE method and its kinematic ground control point (KGCP) concept over conventional corridor mapping methods.
The mapKITE and the conventional method delivered comparable accuracy results — the difference being that the latter requires a dense set of surveyed ground control points (GCPs) while mapKITE does the job with almost no GCPs.
For this purpose, a 4-kilometer segment of the Rodovia Raposo Tavares in São Paulo state was populated with a set of 37 evenly distributed, signalized, accurately surveyed ground points. The set was divided into two subsets of 23 GCPs and 14 ground check points (GChPs) — the ground truth — respectively. The 4-km road segment was also covered by 189 drone images and their corresponding 189 KGCPs. The image set was processed as a conventional aerial corridor block:
with the integrated sensor orientation (ISO) method in a 23 GCP + 14 GChP configuration, and
as a mapKITE aerial corridor block in a 4 GCP + 14 GChP + 189 KGCP configuration.
The two processes produced similar accuracy results: mean (μ), empirical standard deviation (σ) and root mean square (rms) error of the photogrammetric determination of the horizontal (EN) and vertical (h) coordinates of the GChPs against the ground truth. (All units are stated in millimeters.)
The mapKITE configuration uses only four GCPs (two at each end of the road segment) in contrast to the 23 GCPs of the conventional method. Nominal flying height of the drone was 120 meters above ground, producing an average ground sampling distance (GSD) of 2.3 cm. Forward image overlap was 80% resulting in a base-to-height ratio of 0.157.
MapKITE is a GeoNumerics patented method for 3-dimensional corridor mapping that combines the two latest geodata acquisition methods, terrestrial mobile mapping and aerial drone-based mapping. MapKITE is a tandem terrestrial-aerial mapping method and system composed of:
a terrestrial mobile mapping system (land vehicle and sensors) carrying
an optical metric target on its roof;
a drone aerial mapping system; and
a real-time virtual tether and post-mission software.
In a mapKITE mission, the drone follows the land vehicle, and thus the vehicle target becomes a kinematic ground control point visible and measurable on each image. It is a high-accuracy, high-resolution Earth observation method. MapKITE combines the advantages of mobile land-based encompassing images and 3D point clouds. MapKITE combines the advantages of mobile land-based (manned) and aerial drone (unmanned) mapping systems.
GeoNumerics (Castelldefels, Spain) is a research and development company specializing in geomatics and accurate navigation.
ENGEMAP (Assis, Sao Paolo, Brazil) is one of the largest and oldest mapping companies in Brazil. It has more than 100 employees, three aircraft, two mapping land vehicles, a number of rotary- and fixed-wing drones and a record of accomplished mapping and cadastral projects. ENGEMAP is officially authorized by the Brazilian Ministry of Defence (MD) and the Brazilian Department of Airspace Control (DECEA) to conduct mapKITE commercial flights in Brazil.
MANUFACTURERS
The mapKite campaign was conducted with a Sensormap SMM terrestrial mobile mapping system and a UAVision UX Spyro drone equipped with a NovAtel OEM2 GNSS dual-frequency receiver with a Maxtena antenna and a Sony α7R camera with a 25-mm camera constant lens. The INS/GNSS system in the Terrestrial Vehicle was a Span-CPT (Novatel) including dual-frequency antenna and DMI wheel sensor.
ISMAEL COLOMINA is chief executive and chief scientist at GeoNumerics. He has a Ph.D. in mathematics from the University of Barcelona.
PERE MOLINA is advanced applications program manager at GeoNumerics. He holds a master’s degree in mathematics from the University of Barcelona and a master’s in photogrammetry and remote sensing from the Institute of Geomatics, Catalonia.
ROBERTO DA SILVA RUY is technical manager at ENGEMAP. He has a Ph.D. from the Universidade Estadual Paulista.
Are drones (UAVs) a disruptive or constructive technology for high-precision mapping that yields practical, actionable results for the end user/customer?
Ismael Colomina
“More constructive than disruptive. Drone mapping is opening new markets that, to a large extent, were not serviceable by conventional manned flights. On the other hand, the profound changes — and crisis — in the mapping business were not produced by drones.” Ismael Colomina GeoNumerics
Jean-Marie Sleewaegen
“Drones have dramatically reshaped the surveying and mapping industry. Combined with reliable positioning and recent advancements in high-resolution cameras, photogrammetry and computer vision, drones now enable high-accuracy mapping faster and at much lower cost than conventional mapping techniques.” Jean-Marie Sleewaegen Septentrio
Jules McNeff
“Drones can be constructive augmentations to high-precision map products because of their ready access to diverse locations. Drone imagery can document real-time physical changes that affect mapping applications during natural disasters or other events — but images alone aren’t maps without a geo-referenced grid such as the U.S. National Grid.” Jules McNeff Overlook Systems Technologies Inc.
Other members of the EAB
Tony Agresta Nearmap
Miguel Amor Hexagon Positioning Intelligence
Thibault Bonnevie SBG Systems
Alison Brown NAVSYS Corporation
Clem Driscoll C.J. Driscoll & Associates
John Fischer Orolia
Ellen Hall Spirent Federal Systems
Terry Moore University of Nottingham
Bradford W. Parkinson Stanford Center for Position,Navigation and Time
