UAV Challenges, Pluses and Minuses — and Your Questions

December 11, 2013  - By

In recent years, we’ve seen explosive growth in the Unmanned Air Vehicle (UAV) market segment, with most on-board navigation systems relying on GNSS or GNSS with inertial aiding. As military budgets decline, interest in civilian commercial applications is growing rapidly. The U.S. Federal Aviation Administration (FAA) recently awarded special type certification to two UAVs for commercial Arctic operations and released a Roadmap for UAV certification. The industry is now poised for the opening of the regulation floodgates to address a growing commercial demand.

On November 21, I hosted a GPS World webcast where industry leaders in GNSS-based navigation for UAVs, for both military and civilian sectors, presented what they are doing in UAV navigation and how they see this exciting market unfolding. A record number attended; for those who were unable to attend, here’s an overview of the GPS World Unmanned Aircraft Navigation webinar, with answers to questions posed at the end of the article. You can still view the entire presentation through GPS World’s Webinar page.

The presenters:

Olivier Casabianca, Business Area Manager of the Trimble GNSS OEM portfolio, which includes both the Trimble and Ashtech receiver module product lines.

Eric Brewer, Senior Systems engineer for Rockwell Collins. He develops and tests guidance, navigation, and control algorithms for unmanned and optionally piloted aircraft.

Neil Gerein of NovAtel, responsible for the navigation warfare product lines, including the GPS anti-jam antenna and SAASM receiver used on unmanned vehicle systems.

Hal Adams, Accord Technology, Chief Operating Officer, and founder of AvValues LLC, which is partnered with Accord Software & Systems, Bangalore, India.

Howard Loewen, president of MicroPilot, which supplies single-board, fully integrated UAV autopilots, ultra lightweight autopilots, and triple redundant UAV autopilots.

Trimble has a wide product line with many applications in UAVs. Its receivers are multi-constellation and multi-frequency with low power and small form-factor. High-precision modules can also use Omnistar precise point positioning (PPP) aiding, have multiple external interfaces, and can provide precise heading and attitude.

Some of the UAV solutions presented include moving baseline (relative) RTK between UAVs, and “swarms” of UAVs, autonomous landing and autonomous refueling between UAVs.

Other applications include precise positioning and full GNSS attitude, and of course the Applanix line of inertial aiding sensors is a key element for aiding and GNSS-denied environments.

With the recent release of the FAA Roadmap for UAV certification and integration into the National Airspace System (NAS), our experts were asked to give us their views on what this means for the industry. Olivier Casabiance highlighted the FAA Modernization and Reform Act, which calls on the FAA to integrate UAS (Unmanned Aircraft Systems) into the NAS by September 2015, and extensive U.S. and European committee activity to develop standards — all leading to a requirement that GPS/GNSS navigation systems for UAVs may need to be FAA TSO (Technical Standard Order) qualified, just as they are now for manned aircraft.

This coming requirement will make extensive use of ADS-B (Automatic Dependence Surveillance Broadcast) and certified receivers, such as the Trimble/Ashtech SkyNav GG12W receiver, which is FAA qualified/certifiable, with firmware developed to RTCA DO-178B level B standards, hardware to DO-208, and meeting DO-217 special category 1 landing requirements.

Eric Brewer then presented Rockwell Collins’ Controlled Technologies products and outlook on unmanned aircraft. Rockwell acquired Athena Technologies some time ago, which specializes in autopilots for unmanned aircraft. Athena is the Center of Excellence for Rockwell Collins in guidance, navigation, control, and estimation technologies. Athena solutions combine GPS-coupled inertial navigation system (INS), air-data sensing, and flight-control computing. Various levels of inertial sensor performance are available with a number of analog/digital interfaces and appropriate levels of hardware environmental qualification. With single string and triplex solutions, this product family has amassed more than one million flight hours in operation. Athena also supplies a range of mission computers which are used with these autopilots.

Athena autopilots.

Athena autopilots.

Athena mission computers.

Athena mission computers.

One of the principle UAS applications for this system is on the Navy’s Small Tactical UAS (Boeing/Insitu Scan Eagle) system, where Rockwell provides the GPS SAASM-RTK (Precision RelNav) System.

STUAS capture.

STUAS capture.

Airborne anti-jam.

Airborne anti-jam.

Each system consists of both base-station and airborne modules integrating the Rockwell 24-channel all-in-view tracking and navigation L1/L2 SAASM P-code GPS receiver (MPE-S Type II), with an external processor running custom RTK software. It provides better than 20-cm (1 sigma) 3-D relative position accuracy for a baseline of up to 30 km. Rockwell also has a number of GPS “hardening” anti-jam solutions for both airborne and missile applications.

Looking ahead, Rockwell sees reduced growth in the UAS domestic military markets and a potential split in UAS development roadmaps. Larger higher reliability, higher complexity systems may move toward NAS integration and FAA compliance, while significantly smaller and cheaper systems may end up restricted to applications outside the NAS.

Neil Gerein provided an overview of NovAtel’s receivers and capabilities, and highlighted some of NovAtel’s UAV applications. NovAtel’s OEM6 series of receivers comes in a number of different configurations with comprehensive support for all current and upcoming GPS, GLONASS, Galileo and BeiDou satellite signals.


These receivers find (or could find) applications in UAV precision landing, payload sensor positioning, and civil anti-spoofing. And the OEM625S SAASM receiver combines civil L1/L2 GPS (including GLONASS and Galileo) with the L-3 IEC XFACTOR SAASM capability for military UAV precision navigation and landing.

Align heading generates high-precision heading and pitch angles between two receivers for real-time navigation for rotary-wing aircraft, enabling precise capture into nets and for other retrieval/capture systems. Align relative positioning generates a high-precision 3-D vector between two or more mobile receivers for high-precision monitoring and automation.

NovAtel also has the SPAN line of GPS/Inertial solutions, which may be used on UAVs for intelligence, surveillance, target acquisition, reconnaissance, airborne mapping, and shipboard landings. The GAJT-AE compact null forming electronics for UAS and other small platforms provides protection of GPS L1 and L2 from interfering sources and works with a variety of four-element antenna arrays enabling flexible installation options.

GAJT-AE anti-jam system.

GAJT-AE anti-jam system.

Gerein thinks that UAV growth has been largely due to affordability and ease of use, and allowing UAVs to have regular access to the NAS will create even more growth. The existing FAA timelines are aggressive, considering the number of interested parties, so equipment suppliers should work closely with FAA to ensure that the level of certification is appropriate for the safety of the public, while remaining affordable and practical so that the industry is not stifled.

Next, Hal Adams from Accord Technology gave his views on navigation for UAVs. Accord Technology has its base in Phoenix, with facilities in Anchorage, Alaska, while the principle R&D base is in Bangalore, India. The Accord NexNav receiver is airborne-qualified and is sold as an end-item enclosure and as a receiver board, and the NexNav-mini variant is sold as a receiver card for OEM integration.

These receivers are qualified to RTCA DO-178B software and DO-254 hardware and meet FAA TSOA (C145c) requirements. So they are already at the required standard for manned (GA) aircraft use — integrators wishing to move towards FAA compliance may be able to reduce the work to meet vehicle certification requirements by incorporating receivers such as these in their UAVs.

Adams reviewed the FAA’s plans to implement ADS-B throughout the U.S., and indicated that all aircraft operating in the NAS will be required to equip and use ADS-B by 2020. The FAA is rolling out the ADS-B ground infrastructure, and air-traffic operations are already underway using ADS-B in Alaska. ADS-B requires an approved GPS source meeting FAA AC 20-165A providing it with the necessary data — and the NexNav products apparently already meet this requirement.

As far as where the FAA is going on UAVs and how regulations will affect them, Adams related statements from the FAA that UAVs, “Must be as safe as manned aircraft, including systems.”

He felt, therefore, that UAS will have to comply or operate separately, outside of the air-traffic system. UAVs wishing to operate in the NAS will likely have to be certified and approved by the FAA to NextGen standards. NextGen is the next-generation Air Traffic Control system under development by FAA.

Finally, Howard Loewen, president of MicroPilot, provided insight into MicroPilot’s UAS products, the company’s use of GNSS, and how it sees things evolving. MicroPilot has been around since 1995, so it has already watched the UAS market evolve. MicroPilot develops and fields autopilots for manned and unmanned aircraft using GPS in a number of different configurations, including consumer-level GPS, carrier-phase RTK, and moving baseline RTK.

UAVs have a number of challenges to overcome — RF frequency allocations for control links, privacy concerns, meeting security and regulatory requirements, incorporating airborne standards into their development, developing “see-and-be-seen” (sense and avoid) technology, and competing with existing manned aircraft capability for their business. Loewen made some interesting comparisons between the use of UAVs and that of (manned) Cessna operations. While a Cessna payload can be significant, there are few flight restrictions and the technology is mature. UAVs are relatively immature and have both payload and flight restrictions. The market will have to decide if the potential for lower UAVs operating costs will be enough to win out.

Nevertheless, Micropilot is already preparing for the requirements of FAA certification for UAS autopilots and has developed hardware and software verification/validation tools.

Loewen sees pluses and minuses for UAVs in the future – FAA selection of UAS test sites will continue to be delayed, standards will begin to emerge from European efforts to integrate UAS into their airspace (maybe sooner than in the U.S,?), small UAS (sUAS) will continue to be popular in areas of the world where regulations have yet to be put in place, and there is even the possibility that the FAA may back off trying to control sUAS (because of the commercial volume?), that large UAS such as the Predator will provide no advantage over Cessna-type manned aircraft, and that the FAA will continue to delay regulations as it concerns itself over details that may not seem to be totally relevant — like the “cockpit door” issue highlighted in the recent FAA Roadmap.

There was a great deal of interest from a large audience for the webcast, and we received a number of questions before and during the webcast. Our experts did their best to provide answers wherever possible, and this Q&A is presented at the end of this article.

Overall, we seem to have covered a lot of ground in the webcast on UAV navigation – providing an insight into both existing capabilities and how some key industry leaders see the future unfolding. Almost every day there are new and interesting developments – I’m sure by now we’ve all seen the video clips from 60 Minutes and how Amazon demonstrated delivery within 30 minutes using small UAVs to pick up packages at their distribution plant and deposit them on the buyer’s doorstep, and of course the potential delivery of hot pizza right to your door.


Let’s see if some of this stuff sticks and we can actually make this sort of progress safely, usefully and efficiently.

Tony Murfin
GNSS Aerospace

Webinar Q&A

Here are some brief responses for questions received. Questions were submitted during the webinar by the audience, and answered post-webinar, in writing, by the panelists and moderator. The views expressed are those of the authors and are not necessarily supported by GPS World.

Q:What are the safety consequences for self-navigating, self-separating unmanned aircraft?

A: No rules yet published, but expected that UAS will be required to meet the same flight regulations as manned aircraft.

Q: We have light rail and buses. Is any company, agency one planning on using this technology to monitor these type of vehicles movements for security, prediction arrival, etc.?

A: This is a typical application for UAS — not aware of any current operations like this

Q: Could we use UAVs to survey bird species that go every year to the same spot to breed? I am thinking specifically on Greater Sage-Grouse.

A: This is a typical application for UAS – several wild life monitoring operations already exist

Q: I was told by a UAV manufacturer that they are not illegal if you fly below 400′. Is that true?

A: No UAS rules yet, but someone was just indicted by FAA for ‘buzzing’ building at low altitude in New York.

Q: What are the rules for the use in the private industry?

A: Rules being developed by FAA for civil operations — U.S. Congress has set deadline for integration of UAS into civil airspace by September 2015. FAA just published a “Roadmap” for how they see this process going forward.

Q: Why should general aviation pilots not be concerned about UAV collisions?

A: Rules are needed for the operation of UAS in civil airspace & these are expected to be equivalent to those for General Aviation aircraft.

Q: What about Canadian air regulation?

A: Permission to fly a UAV in Canadian air space is regulated by Transport Canada.  Specifically, UAV operators must have an approved Special Flight Operation Certificate (SFOC) from Transport Canada before commencing a UAV flight.

Q: Is machine learning the most significant part of the UAN?

A: Do you mean UAS? Not really – most systems are pre-programmed and well defined. For use in civil airspace all systems on an aircraft need to be fixed and pre-qualified and approved – no room for changes in or-board systems.

Q: What are the flight rules in Alaska near airports or military controlled airspace for UAVs?

A: There is a task force working this issue and other UAS issues, in Alaska, being coordinated by Representative Shelley Hughes. Work in progress can be accessed via

Q: Accuracy and risk involvement?

A: GPS and other GNSS basic unaided accuracy is several meters, with PPP or L-Band satellite corrections we get close to 1 meter and with Real Time Kinematic we can get a few centimeters. Risk (?) is always a good question, but that’s what the FAA and other certification/regulation agencies are there to ensure that risk is minimized. People have been using GPS/GNSS for over 20 years, and there are very few incidents of systems failures, rather temporary loss of signal, or degraded accuracy. This is why manned aircraft which use GPS have back-up systems and UAS will need similar redundant systems.

Q: What is the application of mUAS for agriculture and surveying?

A: Lot of activity in high precision surveying using UAS is already underway. Crop spraying using helicopter UAS has been in use in Japan for many years – its expected use will grow exponentially in these areas when there is open access to airspace.

Q: What FAA regulations prevent organizations from flying at low elevations, if any?

A: No rules yet published, but expected that UAS will be required to meet the same flight regulations as manned aircraft. There is a chart in Accord’s briefing showing the layout of NAS with the ADS-B requirements.

Q: How do payload applications access GNSS data, Position, Navigation, Timing, and utilize the precise 1PPS for synchronization if the Navigation function is NOT to be compromised?

A: Payload applications and the navigation function typically use separate GNSS receivers to ensure the navigation function is not compromised. Actually, for manned aircraft ADS-B, per FAA the ADS-B GPS source must meet AC 20-165A and can be independent of nav functions, including GPS based navigators. FAA will know “exactly where the platform is “lost” and to a high degree of confidence.”

Q: GPS spoofing has been demonstrated by the University of Texas as an effective means to redirect a drone aircraft. What is the industry doing to protect against command/control & navigation hijacking?

A: UAVs operated by the US Government and Allied Forces can use SAASM receivers to protect against spoofing.  For civil user, multi-GNSS receivers with positioning backups such as inertial technology are also effective against spoofing attacks.

As mentioned above, a SAASM is the best way to prevent spoofing.  Jamming is also of particular concern, and Antijam GPS technology is a good way to mitigate the effects of jamming.

Q: What is the best technology to pursue as a backup to GPS? (e.g. D-LORAN, Magnetic Field Nav., Cell Tower Triangulation, etc.)

A: GNSS+Inertial is a way to backup GNSS only in GNSS denied environments. Could be use to augment the information (heading / attitude on top of position) or for continuous positioning…

Procedures are the primary back-up for manned aircraft. If I loose transponder or comms, etc., there is a procedure for operations in those events. If I loose comms the FAA increases separation, clears airspace, etc., to help insure no conflicts. UAS will likely have to have some mitigation like manned procedures. Of course, with a person on the flight deck, it is a somewhat different. I think there will have to be new considerations, like lose of link to the UAS and alternative on the platform and with the NAS manager (ATC). If a pilot looses consciousness on the flight deck, it is kind of like a UAS loosing the command link. So, what happens with person on flight deck if that person cannot operate the aircraft? Seems problematic to resolve or mitigate.

This is a hot topic of research.  Some current solutions include using Magnetometers and Deduced Reckoning (i.e. using a wind estimate and airspeed measurements).  There is also research into using image-based navigation (there are some details about this in Rockwell slides).

Q: Could be GNSS a stand-alone sensor for navigation, and what is the GNSS coverage above 80 N/S parallel?

A: Free Trimble online tool available to make simulations and see the coverage of various constellations and the impact of adding constellations:

Actually, during GBAS International Working Group session in Seattle this summer there were a couple of presentation regarding ionospheric effects on GNSS which seem to support the following statement:

Challenges for GNSS in the Arctic

For GNSS, presently GPS and GLONASS but in the future also for Galileo, the performance in the Arctic region is reduced compared to the performance obtained by users at mid-latitudes. The reasons are mainly the satellite-receiver geometry and the ionospheric effects on the satellite signals, but also users do not have the benefits of satellite based augmentation systems (SBAS) at a larger scale.

Q: el % de errores y eficases de estos, y si en poco tiempo podrian activarse y desaptivarse automaticamente segun sea el caso

A: We didn’t have any Spanish speakers, but this is our best-guess answer. Most GNSS receivers have some form of Receiver Autonomous Integrity Monitoring (RAIM) and airborne systems need to conform to Minimum Operational Performance Standards (MOPS), which define error rates for all known situations.

Q: Which industries will see the greatest increase in usage of unmanned systems once the FAA opens up regulations for integrating unmanned aerial vehicles into society?

A: Its likely that the most intense civilian applications of UAS have yet to be invented. But we do know that crop & pipeline monitoring, precision and non-precision surveying, flying-camera applications for all forms of news and security, potential package delivery, and even vehicle traffic monitoring are popular applications waiting for more open access to airspace.

Q: Per the FAA’s recently released Civil UAS Roadmap, what exactly constitutes a “small UAS (sUAS) with very limited operational range?”

A: It seems that the FAA has yet to publish regulations which would define sUAS. These apparently have been drafted and are still under consideration by FAA.

Q: Per the FAA’s recently released Civil UAS Roadmap, what exactly constitutes a “small UAS (sUAS) with very limited operational range?”

A: The FAA has yet to publish regulations which would define sUAS. These apparently have been drafted for some time and are still under consideration by FAA.

Q: What is the risk of the aircraft crashing due to a last minute wind gust as it approaches the wire (referring to the Rockwell Collins product used to land the UAV on the wire on the ship)?

A: The safety is evaluated through both simulation and flight testing.  The wind gust disturbance rejection is a primary constraint, and the operational envelope (wind envelope, ship motion, wind over deck, capture speed) is selected to ensure that risks are maintained at acceptably low levels.

Q: Question for all: Can any of these products produce primitive data (pseudorange, carrier phase) prior to demodulation of an ephemeris. (We are looking for the fastest possible acquisition time.)

A: Yes, we (Rockwell Collins) have products available which can output uncorrected pseudorange and carrier phase before receipt of ephemeris data.  Feel free to email me for more details.

Q: Have any of these products been used in missile range-safety applications? (Missile = BIG UAS)

A: Rockwell Collins’ weapons receivers are used in a variety of precision guided weapons.  See, or feel free to email for more details.

Q: Could you define the NAS?


Our apologies if we had not yet received responses to your question in time for this publication.


This article is tagged with , and posted in Opinions

About the Author: Tony Murfin

Tony Murfin is managing consultant for GNSS Aerospace LLC, Florida. Murfin provides business development consulting services to companies involved in GNSS products and markets, and writes for GPS World as the OEM Professional contributing editor. Previously, Murfin worked for NovAtel Inc. in Calgary, Canada, as vice president of Business Development; for CMC Electronics in Montreal, Canada, as business development manager, product manager, software manger and software engineer; for CAE in Montreal as simulation software engineer; and for BAe in Warton, UK, as senior avionics engineer. Murfin has a B.Sc. from the University of Manchester Institute of Science and Technology in the UK, and is a UK Chartered Engineer (CEng MIET).

9 Comments on "UAV Challenges, Pluses and Minuses — and Your Questions"

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  1. John says:

    I am just a rancher using my airplane to fly over the ranch and vicinity and other localities. If there’s a UAV doing a aerial survey to look at wetlands, prairie dog towns and the like, is it going to break off from its survey route to avoid me?

    • Eric Gakstatter says:

      That is the $1,000,000 question. The FAA is ultra-conservative, so I think that’s why ADS-B is part of the discussion.

      But, I think the bigger challenge are going to be the inexpensive, small UAVs deployed by farmers or local consultants for mapping. While the FAA thinks their rules are clear, just this week I heard a UAV vendor tell farmers at a small conference that it is legal for farmers to fly UAVs above their own property. The FAA will say this is clearly not allowed based on the current FAA rules.

      However, the fact is that the FAA rules are ambiguous. Some even claim that current FAA rules are only policy, and not enforceable regulation. The judicial system will have to rule on this. I’ll have a detailed article about this in Geospatial Solutions later this month.

      • Corey Zeimen says:

        Object avoidance technology is certainly in the works for the commercial UAV market as prototypes are already out there and reliance on GPS for navigation decreases.

        • Marcus UAV says:

          Also, right now smaller commercial UAV’s are flown by operators that can take control at a moments notice so the danger is not near what you may think.

          Current regulations do say it is possible to fly LEGALLY if you keep it under 400 ft, within line of sight, and can take physical control over the aircraft at any time which all of our products offer.

  2. Jim Horn says:

    Just to note – the Navy’s Small Tactical UAS (STUAS) is not the Insitu ScanEagle but the Insitu RQ-21A, similar to Insitu’s Integrator. The former has had most of a million combat hours over the years. The latter is a newer, larger and heavier “pickup truck” with much greater payload capability and flexibility. Both use the Skyhook recovery system you describe, for which GPS is a key technology.

  3. Taiwo says:

    Question. Can UAVs be used to carry out geological field mapping hence producing topographical maps? Can It also serve as a spy plane to fight terrorism in Nigeria, snapping photographs,videos and sending back gps location of boko haram terrorists in Nigeria. Will it also have to work with or without a space satellite saving the country millions of dollars?

  4. Taiwo says:

    Can AUVs also find applications in photo geology, geophysic wrt airborne surveys.?