Can “AltPNT” Actually Exchange GPS?

Between the escalating conflicts in Ukraine and the Center East and the rising geopolitical competitors between the US and China, there was a collective realization concerning the fragility of GPS and different World Navigation Satellite tv for pc Programs (GNSS).

Spoofing and jamming haven’t solely bedeviled positioning on the battlefield, however they’ve additionally spilled over into civilian life by wreaking havoc on industrial aviation. The challenges of working GPS in hostile environments have led to a name for AltPNT — Different Positioning, Navigation and Timing — that doesn’t depend on the GPS constellation.

We at the moment are starting to see a proliferation of applied sciences that target non-GPS navigation. This can be a important departure from the current previous, the place the main target was extra about “augmenting” PNT as a substitute of making an alternate that’s completely disconnected from GNSS. 

However how possible is that this notion of totally changing GNSS? Realistically, there isn’t a singular resolution to exchange GPS, however we will make it extra resilient with complementary applied sciences.

Important necessities of AltPNT 

It is necessary that we be clear about what actually constitutes AltPNT, in order to not confuse it with augmentative “AugPNT.” 

To start with, the expertise should be really unbiased of the GPS constellation and should not require periodic GPS updates to be able to keep away from drift. It should even be akin to GPS in accuracy, pace and international protection. And it shouldn’t be inclined to the identical issues that might degrade or deny GPS alerts. In any other case, what’s the purpose?

Few present applied sciences meet this definition. Most AltPNT options are merely dietary supplements to GPS, not replacements for it. As Nikki Markiel, senior GEOINT authority for geomatics on the Nationwide Geospatial-Intelligence Company just lately instructed Breaking Protection, “There isn’t a silver bullet” in the case of changing GPS.

Satellite tv for pc alternate options

Non-public firms like Xona and TrustPoint are constructing new industrial PNT companies utilizing low Earth orbit (LEO) satellite tv for pc constellations. Researchers have additionally found that SpaceX’s Starlink satellites could possibly be used to ship PNT companies from LEO.

As a part of a multilayer satellite tv for pc navigation (satnav) system, these constellations supply lots of promising potential. Because of their decrease place in orbit, they will ship sooner sign transmission, decreased latency, greater sign power and higher positioning accuracy over medium-Earth orbit (MEO) GNSS satellites. This mix will enhance the expertise for customers. They may additionally spur improvement in superior expertise fields like autonomous autos and augmented actuality which require extra exact PNT measurements than GPS/GNSS can supply.

However LEO PNT satellite tv for pc constellations will not be with out drawbacks — and dangers. 

Crucial situation is value. Due to their LEO orbits, these companies would require bigger constellations to realize international protection. Additionally they have a decrease lifespan than medium Earth orbit (MEO) satellites and subsequently require extra frequent replacements and repairs. The necessity for frequent handoffs between satellites additionally creates greater operational prices and complexities.

A big constellation (with supporting floor stations) additionally presents a bigger assault floor for cyber warfare. And whereas LEO satellites produce stronger alerts than MEO satellites, they’re nonetheless weak to malicious interference, resembling jamming and spoofing. 

LEO PNT satellites additionally face higher issues with atmospheric interference, particularly ionospheric and tropospheric delay. As a result of LEO is a extra crowded working surroundings, the dangers of unintentional collisions with different satellites and area particles are at the very least three orders of magnitude higher than in MEO. 

Aviation alternate options

Within the civilian enviornment, essentially the most important impression from GPS denial has actually been within the aviation sector. 

So what are the choices? Most industrial airways have supplemental programs that improve and enhance GPS/GNSS-supplied PNT knowledge, such because the Instrument Touchdown System, Floor Primarily based Augmentation System), Huge Space Augmentation System, Distance Measuring Tools, Non-Directional Beacons and VHF Omnidirectional Vary.

One of the vital important non-GPS capabilities comes from Inertial Navigation Programs (INS), which most airways depend on as their main backup to GPS. This expertise makes use of accelerators, gyroscopes, barometric altimeters and magnetometers to calculate correct and dependable PNT knowledge. 

Nonetheless, there are two main limitations with INS that undermine its capability to exchange GPS: the necessity for preliminary PNT knowledge from an exterior supply like GPS, and the tendency for INS to float if it doesn’t obtain periodic GPS updates. The latter could possibly be considerably decreased by new quantum-enabled INS applied sciences. Nonetheless, it’s nonetheless too early to inform how efficient this will probably be. 

Terrestrial alternate options

One other different functionality is eLORAN: a contemporary implementation of the hyperbolic radio navigation system initially developed within the Forties. It makes use of a community of mounted terrestrial beacons, and its alerts are stronger and extra resilient to jamming and spoofing than GPS. 

Nonetheless, eLORAN has a number of drawbacks. It’s largely restricted to land and littoral areas, it requires a heavy infrastructure funding and it solely supplies lateral positioning, not vertical navigation functionality. Nonetheless, it’s price noting that the U.S. navy is presently experimenting with new deployments of eLORAN that might present full protection throughout the continental U.S. with solely three terminal stations.

Terrain-based navigation (TBN) is one other promising expertise that makes use of sensor enter matched towards pre-mapped terrain to information navigational programs. TBN has a set reference based mostly on the altitude of the terrain that has already been mapped to be able to scale back the potential for drift. Nonetheless, one necessary limitation with TBN is that it’s much less efficient in flat terrain, the place there may be much less altitudinal variation, as is the case in Ukraine. Moreover, heavy bombing, particularly in cities, can change terrain maps and complicate navigation. It’s potential to make use of real-time mapping with SLAM (simultaneous localization and mapping) — however that solely supplies relative positioning, so the person will nonetheless want an anchor with recognized positions.

Different alternate options

Different rising applied sciences are additionally coming into the image, and should sometime function viable GPS alternate options. 

One of many extra thrilling areas of improvement is in pc imaginative and prescient expertise. Whereas this can be a broad subject, it has rapid functions in PNT with Visible Positioning Programs (VPS) — already in use by such firms as Google, Meta, Apple, Microsoft, Snap and Niantic. 

VPS works by matching pixels seen by way of the digital camera with pixels in a characteristic database to calculate place and navigation. For the reason that place is tied to an actual world coordinate system, it could possibly present persistent monitoring wherever a person goes. Nonetheless, to ensure that this to work, all of the pixels usually need to be mapped out forward of time with extremely correct geospatial coordinates. When working at a big geographic scale like a metropolis or area, this presents a big logistical and price problem. It additionally poses distinctive challenges in a wartime surroundings — in spite of everything, if an space’s key landmarks are destroyed by bombs, missiles or hearth, the pre-mapped pixels will not be correct. 

These elements make a totally unbiased system fairly troublesome, which is why essentially the most superior tech firms on the earth take a layered method that integrates VPS with different programs.

LiDAR, or mild detection and ranging, is one other promising expertise. When fused with INS, this expertise might briefly help navigation in a GPS denied surroundings. 

LiDAR emits pulsed mild waves from a laser to create a real-time 3D map of the surroundings. This permits it to precisely detect obstacles and decide depth. By incorporating INS, it could possibly additionally calculate place , orientation and velocity. This navigation system is also additional enhanced by integrating VPS and different applied sciences like radar. 

However to be able to function over massive geographies, LiDAR usually must have the area already mapped in order that the gadget can localize. This may be costly and in addition causes limitations because it requires a transparent line of sight to perform correctly (which will be impeded by obstacles and climate circumstances) and its effectiveness diminishes over longer ranges.

In the end, none of those applied sciences on their very own supply an entire substitute for GPS or different present GNSS. It’s necessary that we not confuse the advertising and marketing to ditch satellites with the fact of how exhausting and complicated it truly is to ascertain a real AltPNT system that may preserve excessive accuracy and reliability within the absence of GPS or different GNSS. The fact is that we’d like a layered method to PNT that interconnects a number of applied sciences to allow sleek degradation in hostile circumstances.

There are lots of proficient folks creating new AltPNT applied sciences, and a substitute for GPS/GNSS might be in our future. However within the meantime, we should proceed to put money into a extra resilient and sturdy GPS system, particularly by creating a range of AugPNT applied sciences that would be the key to safe navigation years down the road. 

Sean Gorman is the CEO and cofounder of Zephr, a developer of next-gen location-based options. Gorman has a greater than 20-year background as a researcher, entrepreneur, tutorial and subject material knowledgeable within the subject of geospatial knowledge science and its nationwide safety implications. He’s the previous engineering supervisor for Snap’s Map group, former Chief Strategist for ESRI’s DC Improvement Heart, founding father of Pixel8earth, GeoIQ and Timbr.io, and a Director at Maxar. Gorman served as a subject knowledgeable for the DHS Crucial Infrastructure Process Pressure and Homeland Safety Advisory Council. He’s additionally a former analysis professor at George Mason College.

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