What if GPS Fails?

David H. Williams, President, E911-LBS Consulting, dwilliams@LBSGlobe.com

October 7, 2022 (Updated 10/10/22)

We depend on GPS for much more than we realize. What do we do if it no longer works?

This article is the first in a series exploring how GPS has changed key aspects of our world, and what we might do to prepare for if it is disrupted or no longer is available. This first article introduces the issue and provides an overview of how GPS is used in ways we might not be aware of. Subsequent articles will focus on particular uses, how companies and government agencies might prepare backups for GPS outages, and how they and everyday users can prepare for the temporary and even long-term absence of GPS.

Over the last 15 years, the United States Global Positioning System (GPS) has become a well-known fixture in our wireless society. More specifically, GPS and other location-based technologies, systems, and applications, including satellite navigation systems from Europe, China, Russia, Japan and India (collectively known as GNSS — Global Navigation Satellite Systems), have become an integral part of our everyday work and personal systems and processes, and embedded in how our governments and even society as a whole function.[1]

However, recently we got a taste as to what might happen if satellite systems, in particular GPS, were to fail, be sabotaged, or otherwise no longer function. In January of 2022 this happened in the area over the Denver International Airport:

Air Traffic Control issued a notice advising pilots of problems with GPS reception spanning about 8,000 square miles in the Denver area.

The advisory, posted at 10:33 p.m. Denver time, said GPS was unreliable within a 50-nautical-mile radius of the Denver International Airport. Interference was likely to be experienced by aircraft on the ground and as high as 40,000 feet above sea level.[2]

A variety of issues resulting from this 33.5 hour outage were reported, including potential collision concerns. Disturbingly, a cause(s) for this disruption has still not yet been disclosed by authorities. While thankfully there were no major incidents, this outage illustrates the degree to which we as a society have grown dependent on GPS and similar systems. With the potential for “man-made” disruptions higher now than ever due to potential Russian and Chinese geopolitical concerns, it would be myopic, indeed fool-hardy to not plan for potential disruptions. To do so, it helps to understand what is enabled by GPS, how GPS can (at least in part) be made up for by other techniques, and of course how it is used — in detail.

What Does GPS Enable?

GPS, and indeed all GNSS systems, are primarily used for outdoor location determination purposes, and though they can work indoors to some degree, they are less reliable or accurate due to line-of-sight issues. Historically they can locate a receiver to about 10 meters (30 feet) accuracy, with new location refinements continuing to make it more precise, down to a few centimeters or less. GPS is generally considered the most reliable, most accurate outdoor location determination technology, and given its prevalence in today’s devices the most ubiquitous and easy to build location-based/aware applications upon.

Further, location is not the only use for GPS. Calculations based on multiple GPS readings can be used for measurements such as (average) speed, heading, bearing, change of movement and direction, distance-to-go, time-to-go, chart plotting, route tracking, and mode, method, and status of transportation (driving on a car on a major highway, walking in a park, being on a plane taking off, etc.). These measurements in turn are used to infer or deduce all sorts of situational awareness and behavior, and enable various forms of app functionality, particularly when combined by other sensor readings. In short, the functionality enabled by GPS forms the core of many applications, and the core of the vast majority of location-based ones.

GPS is actually a constellation of at least 24 satellites operating at any one time, with up to 8 satellites potentially visible at a given place at a given time. At least 3 are needed to determine a person’s location. Put a different way, you don’t need all 24+ satellites to be operational in order to get a location. A partial outage of satellites could result in a partial outage of GPS, potentially becoming operational once those satellites move over the horizon and new (operational) satellites come into view. Thus, unless there is a system-wide outage, affecting all or nearly all satellites, an outage may not last for a long period of time, such as with the Denver airport incident.

That said, to the extent possible, it makes sense to “backup” GPS to provide location readings if GPS is not available, system-wide, and for an extended period. While some outages may indeed be temporary, the more severe ones (e.g. severe solar flare, and the biggest of all — an EMP) will be of much longer duration.

Backup Possibilities for GPS

Before we get into different ways GPS has become integral to our lives, it is helpful to understand these alternatives or backups to GPS. These fall into 4 categories: 1) Terrestrial-based systems; 2) Other satellite systems, 3) Process and Procedures, and 4) Shifting from Absolute to Relative Location and Hybrids.

Terrestrial-based Systems

There are other technologies and methods (“techniques”) for obtaining a device (and an associated human’s) location. These include Wi-Fi Positioning systems (WPS), Cell Tower location, Proximity Beacons, RFID, and Bluetooth relative proximity detection, as well as carrier-centric time-based techniques such as TDOA (Time Difference of Arrival) and AFLT (Advanced Forward Link Trilateration). These will be discussed more in future issues, but overall they do not utilize satellite signals at all, or do so in a very constrained, non-real time limited fashion, and will work in a GPS outage.

The good news is that most phones (particularly Android and iPhone) already have some of these terrestrial location technologies, while carriers and their supported devices have others. The bad news these backup technologies are not always available (particularly Wi-Fi and beacons, which availability and accuracy tends to track population density, and RFID, which requires special infrastructure), are of limited utility (for example, detecting other Bluetooth devices only tells you if you are near someone, not where you are), and/or are not very accurate (particularly cell tower location, which can vary widely depending on the coverage area of the tower). Further, many cell phone applications are highly dependent on GPS-level accuracy, assume its near ubiquity in devices being able to use it, and are not designed for the possibility of GPS going out completely, even if an outage is limited in time duration or scope (e.g. number of satellites affected).

Other Satellite Systems

As mentioned, there are several other GNSS systems other than the U.S.’ GPS system. In essence these systems increase the number of satellites that can potentially be seen at any given time, with the implication that if some, but not all satellites, in a given area (e.g. within line of sight of the device), are out, there will still be enough (at least 3 or 4) to get a location fix. The problem is that utilizing these other GNSS requires more sophisticated receivers and software in a given device and support networks, which increases the complexity and cost. Nonetheless, the ability to use other GNSS systems is becoming more common, as is satellite signal refinement and use of inertial sensors that enable accuracy measured in centimeters, not meters/feet.

However, if an outage is due to any sort of attack/sabotage, or if an outage is due to a solar flare or EMP strike (e.g. a high-altitude atmospheric nuclear blast), then all satellites in a given area will likely be disabled, and even the best, ultra-high accuracy GPS systems will not function if the core satellite signaling vanishes. In general, in my Sample Implications/backup ideas discussion, I assume that a “GPS outage” will include all other GNSS systems. This is even more likely in time of war/near war, as it would be very likely that Russia or China will deliberately disable or modify their systems to lessen their utility, much like the U.S. did up to the year 2000 with its Selective Availability program, which deliberately degraded signals to reduce accuracy.

Processes and Procedures

At least in part, for many uses, no GPS means going back to the “old days” before GPS. A simple example is using good-old paper maps instead of Google Maps. The downside of course is that many of the processes and procedures, and the tools they use, have become antique-like — hard to find, and with humans having to relearn their use. In the case of an outage, if these kinds of backup had not already been found, dusted off, and updated for modern use before an outage, they will be of limited use. Hence resurrecting them beforehand will be critical for many business operations, as well as prepared consumers. Of course, the specific processes and procedures will vary depending on the specificGPS use, and can further benefit from the use of relative location, discussed next.

Shift from Absolute to Relative Location or Hybrids

Absolute location is knowing where something/someone is on the face of the Earth, according to some sort of coordinate structure. This is generally an X and Y (and sometimes Z) coordinate set; in practical use this is done via a system that uses degrees of latitude and longitude and that measure the angle between a location and the reference line, namely the equator and Greenwich England, using coordinates according to a global datum scheme (essentially a numbering scheme relative to a geometric representation of the earth with a given reference point and orientation), which for GPS and other GNSS is called the World Geodetic System (WGS 84).

The above is important in that it means that coordinates can exist without using GPS (or GNSS), via a variety of means. Terrestrial systems such as TDOA create coordinates given time of arrival differences from the same source (e.g. a phone/device) to measuring units in different cell towers. If the location, e.g. coordinates, of the cell towers are known, the coordinates of the device can be calculated. No GPS is required. Generally, such calculations are very accurate, though not quite as good as GPS; that said, TDOA has been used for (historically) GSM-based carriers such as AT&T and T-Mobile for the last 20 years for 911 call location determination.

All of the above are still determining absolute location. However, if for some reason terrestrial location techniques such as Wi-Fi positioning or TDOA cannot be used as a backup, or if the accuracy of those techniques is deemed inadequate, there is relative location. Relative location is knowing how far away you are from something/someone else, even if you do not know the absolute coordinates of that thing/person, or yourself. This is done for example in systems that use Bluetooth signals for “proximity detection.” If your device can detect another Bluetooth device, that means you are within 10 meters (30 feet) of that other device (the maximum range of most commonly used Bluetooth signals). With that information, yet no absolute coordinates, you can do a lot of things that absolute location can do. A less technical example, using a local datum scheme, is on major highways, where mile markers in 1/10th of mile increments are posted starting at the border of the state, and incrementing until the highway reaches the other end of the state, when the markers reset back to zero and start over again. A driver of a broken-down car can call for help not knowing anything about their latitude or longitude. Instead, all they need to know is what mile marker they are near, and whether it is an upcoming marker or one they just passed, supplemented by other relative location information such as direction of travel. This kind of roadside emergency system has been used for decades with great success, and again without (and well before) GPS existed. Knowing that the car is at the 85.3-mile marker on Interstate 64 going east in Missouri is all that is needed to render assistance; GPS-generated latitude and longitude coordinates are not needed at all.

Further, if you combine that relative location with some sort of absolute location — a kind of hybrid — you can enable even more functionality. Thus, even if your device doesn’t have GPS or any other direct means of figuring out its absolute location, you can still do so indirectly, using your relative location. For example, if your device can detect a fixed transmitting beacon, transmitting some sort of identifier, your device can then receive that identifier, and look up in a database (via the internet using your wireless carrier) the location of that beacon (the returned information being a latitude/longitude set or even in a local datum like mile marker example above). Then, since there are various ways (such as Bluetooth above) for determining the distance you are from the beacon, you can then calculate your location (absolute or relatively using local datum), based on that range from that now-known location of the beacon. Indeed, well before GPS this type of system was used in aircraft and maritime navigation. Another hybrid would be knowing the absolute location of the highway mile markers; from that a very precise estimate of the location of the broken-down car can be done based on its relative proximity (e.g. about 50 steps, just around the bend going east, etc.) to a marker.

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GPS Time and Associated Vulnerabilities (updated)

Special Note: having a precise time source, e.g. clock, is critical for many applications in general and specifically in doing location calculations based on GPS signals, which are in turn sourced by atomic clocks in each satellite, with the time included in each GPS signal, which is broadcast continuously. If GPS goes down, particularly in a widespread outage, then the ability to use GPS-based time goes away too.

The ramifications of losing GPS time by itself are potentially enormous, if relatively easy to backup. GPS time as the time source is used in many places, not only within the wireless network itself and in calibration of electronic devices (including GPS signals). For example, it is used in such diverse applications as doppler radar calculations (the U.S. Federal Aviation Administration (FAA) uses GPS to synchronize reporting of hazardous weather from its 45 Terminal Doppler Weather Radars located throughout the United States), digital radio broadcasting (ensuring that Internet-sent music data bits arrive and are presented to the user in the right order), and scheduling-based applications. If GPS goes down, there is even a chance that wireless telephone and data networks will go down, as many such networks use GPS time to keep all of their base stations in perfect synchronization and mobile handsets to share limited radio spectrum more efficiently.

Of particular note is that many businesses, including financial institutions, worldwide use GPS to time-stamp their business and financial transactions, providing a consistent, accurate, and synchronized way to maintain records and ensure their traceability. Specifically, major financial institutions use GPS to obtain precise time for setting internal clocks used to create financial transaction timestamps. Large and small businesses are turning to automated systems that can track, update, and manage multiple transactions made by a global network of customers, and these require accurate timing information available through GPS.

GPS time is even imbedded deeply in our electrical grid. Power generation companies and utilities use GPS time, including placing GPS-based time synchronization devices in power plants and substations. Through the analysis of the precise timing of an electrical anomaly as it propagates through a grid, engineers can trace back the exact location of a power line break.[3]

The utility of any of the above backup techniques will depend heavily on the specifics of what GPS time is being used for. At a minimum, the ability for ground-based electronics to update/synchronize their clocks goes away in an outage, and eventually will become out-of-sync with other devices. If the app relies totally on GPS (e.g. in essence the GPS clock is its clock), the app will break down completely.

The backup in this case is relatively easy; there are ground-based atomic clocks to synchronize to — the app will need to switch to one of those clocks in an outage. However, this is probably the “easiest” backup to do; many other uses of GPS will require much more sophisticated and/or well thought out backups, depending on the specifics of the GPS usage.

Update on backup: I understated the above GPS backup possibility — it is harder than it seems above in the preceding paragraph. The apps above use GPS time as a kind of broadcast, always running, constantly available clock that they can “grab” the time anytime they want, doing the cyber equivalent of just taking a quick look out the window for the latest time.

However, to use a terrestrial atomic clock, there needs to be connectivity through the internet to access the current time. Thus, it won’t work if there is no connectivity, or won’t work well if there is some sort of delay in the transmission, or a lot of overhead with obtaining the time. An alternative is having a local clock (or internal to the company master clock) that periodically checks a terrestrial atomic clock and makes any necessary adjustments. Any discrepancies are apt to be small, but keeping it so would require a clock of some sort to be maintained and periodically synchronized by the entity supporting the app using the clock.

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A final, but possibly critical point regarding GPS backups: any backup/replacement for GPS will need to be done not just for companies and the apps and services that they offer, but also take into account the perspective of their customers. Many companies have “trained” their customers to interact with a given company according to GPS-based systems and associated processes and procedures. So any GPS impact assessment and associated backups design will need to include — at a detailed level — understanding in great detail how no GPS will impact those interfaces/interactions with the customer. In fact, many companies have incorporated GPS-enabled customer behavior into their internal processes, sometimes greatly modifying those processes and, conversely, causing the risk of direct customer disruption in a GPS outage. For example, QR codes, used increasingly for event admission and customer routing purposes, can verify the use of the QR codes being used at the right place at the right time via GPS. A good rule of thumb is if a sign-up or registration process asks for location, and in particular asks the customer to allow location to be obtained — then a GPS outage will impact that functionality. Again, the specifics of any backup course will vary by use, discussed next.

What do we use GPS for?

Let’s take a brief look at some of the ways we use GPS, listed roughly in order to degree of common knowledge.

Navigation

Most everyone is familiar with Google Maps, Apple Maps, or other navigation-related apps to guide us to and fro — not just for basic directions but to keep us up-to-date on traffic problems, not only helping us get to our destination efficiently but more broadly becoming an integral part of how we plan and execute our day. Without GPS these applications can become essentially useless, and the potential for future innovations, e.g. driverless cars, is hugely hindered.

Sample Ramification of No GPS: Few people have memorized their local road system, and (arguably) hardly anyone under 40 knows how to read a map. Expect a shift towards using major roads even more than they are now as people stay away from roads they are not familiar with. Delivery fleets will become much harder to manage (discussed more in Supply Chain and Transportation), and emergency/navigation-related services such as OnStar and Ford Assist will become very constrained in their functionality. Dynamic (e.g. changing) information related to navigation will be particularly problematic, such as traffic and road conditions reporting.

Consumer Electronics and Applications

Many consumer location devices, for various reasons, do not have a backup to GPS, such as using Wi-Fi positioning or cell towers to at least gain a location approximation. Devices/apps such as Fitbit are such “GPS-only” devices and will fail completely in an outage. Apps that are phone-based would not be completely out-of-luck, as they can use Wi-Fi positioning, Cell Tower location, and beacons to determine location (these will be discussed more in subsequent articles). Some more specialized or upscale (re: expensive) devices have also expanded beyond the United States GPS system to include other GNSS systems, but their inclusion is still far from widespread.

Many applications that are phone-based will also be impacted, even with backup terrestrial methods. For example, weather reporting is now highly localized, and for less populated areas (particularly rural areas) terrestrial methods can be much less accurate. Further, the business models of many applications that collect location data will be impacted, as they often are heavily dependent on the accuracy of that location data for advertising and add-on sales.

Sample Implications of No GPS: Any time pieces or apps relying on GPS to update/synchronize their time-keeping will gradually become inaccurate (or, if badly designed, stop working completely). Any devices relying solely on GPS for location determination will need to have some sort of backup terrestrial technologies and methods built into their design. Even then, locations will need to be recognized as not as accurate as GPS-sourced locations, or even be viewed as approximate, and functionality adjusted accordingly. High precision applications will need to include various forms of hybrid absolute/relative location, as well as refining/confirmation processes and procedures, to ensure data integrity and accuracy, as well as new statistical methods developed to estimate degrees of precision and (in)accuracy.

Law Enforcement and Public Safety

Many people today have no idea how integral GPS is to law enforcement and general public safety. Need an ambulance? It relies on GPS (yours and theirs) to get to you fast. Need the police? They have been guided to your location (using both their GPS and yours) is some cases for well over 10 years. Indeed, the 911 system is in effect heavily reliant on GPS to function, and in many cases totally reliant on it.

Law enforcement, and subsequent prosecutions (“LE”), have also become dependent on GPS. In the “old” days, LE relied on the location of the cell towers that a phone was connected to, particularly when they engaged in voice calls or texts, as evidence in establishing the “opportunity” for someone to have committed a crime (e.g. John was in the vicinity at the time of the robbery). These kinds of techniques were limited as they often could only use the location of the cell tower to which the person was connected to as a “proxy” for the location of the person itself. This could be off actual location by hundreds of yards or even several miles, introducing obvious limitations in tracking someone down or confidently establishing proximity to a crime in court.

These days, GPS information generated by apps, aided by the fact that nearly all smartphones now have GPS as their primary location determination method, are increasingly becoming the core of the “opportunity” part of the motive, means, and opportunity trifecta. This is particularly helpful to LE in that GPS data is much more accurate than traditional phone data location (derived from cell tower location), and it is collected much more frequently and for a much greater volume of users — particularly for those who spend far more time on the internet than they do on voice calls or texts.

Indeed, “geofence warrants” are becoming increasingly used, where all the location data (most of it GPS, tied to any app that you have allowed to collect location data about you) for all the mobile devices in a given area in a given timeframe, are collected, analyzed and used to identify possible suspects (all without individual warrants being used), and are increasingly used in cases where there are no obvious suspects. Further, during prosecution, GPS data is also often presented undisputed facts in prosecution saying the accused was at a certain place at a certain time, despite there being significant potential for inaccuracies and misinterpretations of data to be made. Without competent technology defense experts to refute these assertions, it can be powerful evidence in establishing opportunity in the minds of a jury, and devestating for the defense case.

A particular onerous problem for public safety in a GPS outage will be the immediate failure of GPS monitoring bracelets for parolees. Many of these systems have no backup, and will essentially become useless bracelets upon a GPS failure. More broadly, the security systems of many capital-intensive machinery (including your car) will be greatly degraded, potentially triggering a dramatic uptick in associated theft.

Sample Implications of no GPS: For public safety there will need to be a renewed emphasis on mile markers and other navigation landmarks for hybrid absolute/relative location determination, as well as renewed use of paper maps. For Law Enforcement it will be back to the old days of policing and dispatch-centered navigation. A major rethinking of our parole system may be needed, with possibly a dramatic reduction in parole based on home confinement and/or exclusion from certain areas needing to occur, and/or a massive increase in person-to-person parole office visits required. Similarly, security of capital-intensive equipment will need to change, requiring more human and physical protections for the assets.

Supply Chain

2 years ago only a small subset of people knew what “supply chain” meant, let alone included. Now of course thanks to COVID and related factors everyone does to some degree. The use of location technologies has been part of every aspect of the supply chain for many years now, from managing raw materials sources to delivering finished goods to the consumer, and everywhere in between.

While a wide variety of location technologies are used in supply chain management, GPS is the core technology, being used for every aspect of the supply chain that involves movement outdoors. From ships to ports to railroads to long-haul trucks to package delivery, GPS is there, not just in the materials/goods themselves, but in the machinery and people involved in it. Without GPS, tracking any/all of that becomes far less efficient, with associated drop-off in delivery reliability, efficiency and security.

The good news is that GPS, due to its line-of-sight limitations, is not used extensively for location purposes inside manufacturing plants, warehouses, and retail stores. These indoor-centric areas use Wi-Fi positioning, RFID, Beacons, and other RTLS (Real-Time Location Systems) that do not use GPS. The bad news is the potential breakdown of the outside location parts of the supply chain, including those parts dependent on GPS time. For example, various instrumentation used throughout supply chains often require precise timing, particularly distributed networks of instruments that must work together to precisely measure common events at key times. GPS-based timing works exceptionally well for any application (even indoor ones) in which precise timing is required by devices that are dispersed over wide geographic areas. That said, as mentioned, finding alternative ground-based, atomic clock sources for such time is relatively easy, and it is still possible to closely track a package or similar item without GPS — FedEx has been doing it for decades (using instead a node-based check-in type system). But for companies that have put all their location and timing eggs in one basket, it will be a very rude awakening to lose GPS.

Sample Implications of No GPS: The presumption of knowing/being able to know where your material, good, or piece of equipment is at any/every point will have to be rethought, and slack built into schedules to account for the resulting (re)introduction of inefficiencies. For field personnel and outside equipment, the ability to monitor and thus schedule their location/usage will become much harder, and managing field human resources as well the risk of loss and/or theft of equipment will become much more difficult. Indeed, the ability to synchronize/coordinate people and “things” will become particularly problematic, as for example formerly synchronized/coordinated receipt of multi-part goods and the people and equipment needed to move or process them become far less precisely timed.

Transportation

The above referenced various forms of transportation-related aspects, but it is worth having a special category to acknowledge the special requirements associated with public transportation, from airlines to railroads/light rail to city and school buses to taxis and ride-sharing. As seen by the opening of this article, even our air traffic control system has been switched over to GPS after decades using other systems. Similarly, rail and public buses have used GPS to build in tremendous efficiencies and flexibility into their systems; without it, and a massive contingency plan for no GPS, these systems will at a minimum become vastly less efficient, and run the risk of localized gridlocks as managers lose track of where their human resources and capital assets are. The explosion of home delivery as a result of COVID will also be disrupted, as highly efficient delivery routes become far less so, resulting in delays in delivery. Bus systems will become far less efficient, and ride-share capabilities likely severely disrupted, as most such systems are based almost entirely on GPS for the location-related functionality. Buses for example have large fleets that must be managed and coordinated. GPS is used on-bus to announce when the next stop is approaching, and can also be used to dynamically change bus schedules for stops that can have highly varying numbers of riders (e.g. after a concert, closing time of venues, etc.). GPS is valuable to riders in knowing their bus is coming, particularly for impaired individuals. Operationally, GPS also forms the core of many fleet operators in tracking equipment usage and needed maintenance.

Sample Implications of No GPS: Besides the issues described in the above navigation section, each individual industry/type of transportation will have its own issues to deal with, as the aviation issues that started this article illustrate. Railroads for example use GPS to synchronize the timing of railroad communication systems, including data transmissions for PTC (Positive Train Control), voice contact between locomotive engineers and dispatchers, and inter-communications among trains, rail stations, ports, and airports. Public bus systems and particularly ride-sharing systems will likely become far less efficient and dependable. And Guaranteed Delivery of packages will become very difficult to achieve without extensive non-GPS systems and processes being well established.

Smart Cities

Many people may not realize it, or think it’s a joke perhaps, but many cities are investing in “smart” infrastructure, of which location (via GPS) is a core enabler. To their credit, city/town use of such infrastructure — particularly outdoors — has greatly helped the efficiency of their operations and their planning and scheduling of upgrades and maintenance, whether it is stoplight coordination or lighting systems scheduling to public buses or managing trash pickups or scheduling and deploying maintenance crews. The bad news is that the “old” (e.g. highly manual) ways of doing things, albeit inefficient, are becoming increasingly forgotten — and will no longer be available if GPS goes down without some advance planning.

City/town governments provide a wide variety of services, many of which are discussed elsewhere in this article, including emergency services/law enforcement, local transportation management, and utilities. Many of their activities extensively involve surveying and mapping (of roads, building permits, zoning, etc.), capabilities now heavily dependent on GPS but historically was not so. Most recently during the COVID pandemic, various government agencies (including local ones) employed various ways of contact tracking, most of which heavily depended on GPS. More sophisticated traffic management capabilities can adjust stop light timing depending on crowdsourcing of car location signals, which are GPS-dependent. Indeed, dynamically managing city services based on usage/volume/traffic can heavily depend on GPS.

Sample Implications of No GPS: For non-real time services, having plans to “go-back-to-the-old-days” would be wise, such as surveying and mapping. For real-time services, either going back to the old days manual processes or implementing various hybrid backups (for example, beacon-based systems) could be adequate substitutes. In any event, for any service, advanced planning and preparation will be key, as any GPS outage would quickly magnify its impact through major volume spikes in demand for city services that would be likely.

Military

The U.S. Military has a double-edged sword with respect to GPS: it is likely the greatest user of it, with many sophisticated applications; but as a consequence, also likely faces the great potential disruption to its strategies, operations, and tactics than any other user. Indeed, GPS was envisioned, designed, implemented, and still operated by the Department of Defense. While I am by no means a military expert, just looking at some of the systems provided by the U.S. to Ukraine, and its precision armaments using GPS, one can deduce a sense of the importance of GPS in these weapons systems. From intelligence gathering, to manpower tracking in deployments, to weapon targeting, to logistics — I suspect there is little in the practical nature of the military that is not now tied to GPS in some way (and, for obvious reasons, are unlikely to use other GNSS systems). Drone technology is particularly dependent on GPS, and highly vulnerable to disruptions, including local jamming.

Recognizing this, the U.S. Military does have numerous other “special” satellites, as well as specialized capabilities within existing GPS satellites that may withstand an outage that impacts the “commercial” side of GPS. But it stands to reason that both a natural occurrence such as a solar flare, or a manmade attack, would impact these operations just as much as the “core” GPS system.

Sample Implications of No GPS: I’m sure the military has all sorts of backup plans for a GPS attack/outage, most of them secret, so I’m not going to presume to anticipate them here. One aspect to consider here though is with respect to GPS jamming — essentially broadcasting other signals on the GPS frequencies — to prevent or mis-calculate location coordinates. Unlike consumer GPS, military GPS components are “hardened” or otherwise have built-in ways of detecting and filtering out fake GPS signals — a capability that consumer GPS devices might consider in their future products. Another aspect to especially consider on both military and civilian ends is how military-aspects of civilian interaction would be impacted by a GPS outage. For example, FEMA, while not a military organization, has dramatically changed its operations over the years to take advantage of GPS capabilities, and civilians in turn have changed what they expect and how they behave towards and interact with authorities as well, becoming more sophisticated in their use of technology in reacting to emergency events. A suddenly “dumber” civilian population from GPS suddenly disappearing would likely cause challenges that didn’t exist before the dramatically higher expectations (and dependencies) of the “GPS generation,” and need to be anticipated and planned for accordingly in any emergency and/or military-related operation on U.S. soil. Indeed, I suspect that the broader chaos-causing events that would accompany any sort of hostile GPS outage would in turn result in at least a limited deployment of reservists in state national guards. A suddenly technology-deprived populous might cause issues beyond the basic crowd-control training of many of these reservists.

Agriculture

Unless inconveniently timed (e.g. during planting or harvest periods, or periods of fertilization/pesticide application), or for an extended period of time, a GPS outage is unlikely to have a major, or at least immediate impact on agriculture. However, if it is “inconveniently” timed, and in particular for a lengthy period of time, an outage could have a major impact on crop yields. A widespread, long-term outage could be catastrophic, as evidenced by major disruptions to Sri Lanka’s agriculture resulting from major, ill-planned changes in agriculture methods. GPS, and more broadly the “Precision Agriculture” that it enables, has had a major impact on productivity and crop yields. There are no real backups, though an extensive beacon-based hybrid could work well given a broad-based deployment of such systems.

Sample Implications of No GPS: Short-term outages again will likely have little impact. Multi-month or longer will require going back to historical methods until some sort of beacon-based system can be deployed, though this may vary significantly by crop and growing geography. But, as a whole in practicality, Precision Agriculture will not likely withstand a long-term GPS outage, and farmers, ag companies, and agriculture agencies should plan accordingly.

Sports, Recreation, and Entertainment

It may come as a shock to many how much GPS has infiltrated sports, recreation, and entertainment in particular. From ski and hiking apps that track your location and how much you’ve done, to golfers planning their next shot, fishermen marking a great fishing spot, to Money Ball type data collecting on the movements and performance of players at various locations, GPS has “infiltrated” many of these. In the entertainment world, there has been a steady progression in location-aware entertainment apps that choose, customizes, or even incorporate your location into the entertainment. This is increasingly true in vehicle-based systems, which are including sophisticated “infotainment” apps into more and more cars as standard equipment. Not coincidentally, knowing your latest location enables those systems to customize ads and even destinations into the overall entertainment experience.

Less obvious entertainment can also use GPS or its components, like its time-keeping. Anyone who gambles knows the importance of timely information (if you have any doubts, watch “The Sting” again). If your key source of information, such as gambling apps or even more generally digital broadcasting sources, uses GPS for their root time-stamping, then a GPS outage could cause major problems (or even opportunities) for highly time-sensitive bets. Again, you can’t assume GPS is only involved in obvious outdoor-location apps — it could appear anywhere in the systems and processes that underlie any app.

Sample Implications of No GPS: Since for most people this aspect of life is not critical, a GPS disruption will be relatively uneventful, unless they have become totally dependent on GPS for their common sense. For example, taking a long hike in a remote area on a hot day while depending on your GPS device to navigate the trails will rapidly become problematic if GPS goes down, and it might be a good idea to have an old-fashioned transistor radio and paper maps (and a lot of water) to get information in case your digital/internet one fails. For companies and service providers in these industries of course no GPS could have a major impact; certainly for non-high precision applications terrestrial-based backups would work well, whereas for high-precision accuracy applications a more elaborate, hybrid backup might be needed, such as placing beacons in numerous places on a golf course or key hiking trails to give guidance to users that come in range.

Conclusion

The above uses are just the GPS usage tip-of-the-iceberg. Odds are your company, agency, or personal life utilizes GPS, and probably much more extensively than you think. For businesses and end user-oriented government agencies in particular, it may be critical to understand fully how it does so, and develop contingency plans accordingly. This may require a different approach to your contingency planning, as it is typically done for individual facilities or product/product lines — not for core infrastructure or individual key enablers, particularly not for such that have never been disrupted in their lifetimes.

But the luxury of assuming enablers such as GPS can never be disrupted is over. For starters, every company needs to do an Impact Assessment as to if, how, when, and where GPS is used in their organization, and take steps to backup (if possible) or at least mitigate the problems that will result in its absence, even going so far to as to practice such backups in various scenarios (varying time period, scope and geographical distribution of various outages, etc.). This includes planning not just for internal operations impact, but how an outage will reflect in the experience of your customer using your GPS-dependent systems and processes.

For individuals, the “to-dos” vary widely. For most people the loss of GPS will be an inconvenience. Maybe a large one, but still just an inconvenience. But it would still be helpful for each person to do their own assessment about how GPS is involved in their life and their family’s lives. At a bare minimum, each family member should know how to manually navigate using paper maps. For the more pessimistic, having a pre-coordinated meeting place for all family members and key friends in the event of an emergency might be a good idea. For the truly concerned, a kind of personal Impact Assessment should be done, ranging from everyday navigation, emergencies, food and medicine, government/public services used, and so forth. Unfortunately, a GPS outage, besides its obvious real impact described above, may be part of broader disruption in what is needed for everyday life (e.g. an attack by a foreign power will not be limited to GPS). Whether it is toilet paper or medicines or something else, odds are everyone will have some essential component of their life impacted by a GPS outage, particularly a long duration and/or one wide in scope.

For better or worse we have become hugely dependent on digital infrastructure, and times are such that we can no longer assume it will always be there when we need it. This I especially true for our use of GPS. Assess, plan, and prepare for an outage — or the run the risk of chaos if one occurs.

Next Issues (roughly every 3 weeks) will discuss in more depth some of these categories of GPS and how their particular issues for particular industries and types of usage might be mitigated in an outage. Alternatives to GPS will be explored in more detail, including Wi-Fi, Cell Towers, and Beacons, and the use of relative location vs. absolute location. Partial outages, e.g. affecting only some satellites and/or satellite systems, will also be discussed.

[1] Unless otherwise specified, GPS is used interchangeably with GNSS for simplicity in this article.

[2] https://www.gpsworld.com/what-happened-to-gps-in-denver/?utm_source=Navigate%21+Weekly+GNSS+News&utm_medium=Newsletter&utm_campaign=NCMCD220921003&oly_enc_id=4458E9027134I1Y

[3] See GPS.gov for more information on various aspects in this article.