It’s use is pretty much ubiquitous as we see it in our cars in the form of built-in navigation systems, our cell phones for both E-911 calling location and navigation by way of various smart phone apps, in chart-plotters in our boats, and in navigation suites in our aircraft. I can access GPS info from a simple GPS Tools app on my smart phone. I can call up maps that can show me where I am and where I want to go. It’s all tied into GPS.
It isn’t just the US that has a GPS satellite constellation. Europe has their own, called Galileo. Russia has GLONASS. China has BeiDou.
However, before those satellite based systems there was LORAN – Long Range Navigation – that used land-based radio transmitters to provide navigation support for ships and aircraft. The system dated back to World War II and had its limitations, though as time and technology got better, so did the usability and reliability of the system. But it still had its limits.
In between LORAN and GPS there was what was called Inertial Guidance Systems, the original ones employed gyroscopes and accelerometers that were used to calculate position and velocity. This was a military system used in aircraft, submarines, and missiles to navigate. As long as the system knew its starting point it could help to navigate that aircraft, submarines, and missiles to a destination. As time has gone by Inertial Guidance has gotten better as the technology developed. Mechanical gyroscopes were replaced with laser gyroscopes, with each mechanical gyro replaced by a loop of optical fiber fed with a laser. Accelerometers which used a mass and inductor to measure the changes in speed in three axes have been replaced by Micro Electro Mechanical integrated circuits, also known as MEMs that were more sensitive to motion. These improvements increased both the sensitivity and accuracy of Inertial Guidance Systems.
One would think that even those systems would be replaced by GPS because of the accuracy of GPS, but you’d be wrong. The one reason Inertial Guidance is still used is because for some application GPS isn’t available. For instance, submarines can’t receive GPS signals while they are submerged. Also, during war it is possible for GPS to be jammed which can make it useless. That’s why the military still uses Inertial Guidance System in bombers, submarines, ballistic missiles, and cruise missiles, just to name a few. But as good as the modern Inertial Guidance Systems are, they still have inaccuracies that will increase over time, something called drift and something that has plagued such systems since the beginning. But those days may soon come to an end if the efforts of the US Naval Research Lab comes to fruition.
Their solution: Quantum Inertial Navigation. (Note: This link takes you to a page that includes a number of articles but the referenced article is on the right-hand side of the page.)
Quantum inertial navigation is a new field of research and development that can increase inertial measurement accuracy by orders of magnitude.With an increase of orders of magnitude in accuracy, that means the error of present commercial systems of 1 nautical mile over a period of 360 hours could be reduced to 0.01 or 0.001 nautical miles over that same 360 hours, or even less.
"Our interferometer operates in a different regime than most other modern implementations of an atom interferometer," said Jonathan Kwolek, Ph.D., a research physicist from the NRL Quantum Optics Section within the Optical Sciences Division. "By operating with cold, continuous atoms, we have opened the door to a number of advantages as well as novel measurement techniques. Ultimately, we would like to use this technology to improve inertial navigation systems, thus reducing our reliance on GPS."
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Depending on the measurement platform, errors in the location estimation will accumulate and result in loss of accurate position information. Current commercially available inertial navigation systems, for example, can navigate with an error accumulation of roughly one nautical mile over 360 hours. NRL intends to develop new technologies to extend that time such that navigational drift does not limit mission duration.
"The field of inertial navigation aims to provide navigation information anywhere GPS is unavailable," said NRL Associate Director of Research for Systems Dr. Gerald Borsuk. "The advent of atom interferometry allows for a novel approach in inertial sensing, which has the potential to address some of the deficiencies in current state-of-the-art technologies."
GPS has become a backbone to the functionality of both our civilian and military world, providing high-accuracy distributed position and timing information anywhere in the world. However, there are certain battlespace environments in which GPS cannot function, such as under water or in space, as well as an increasing threat to GPS availability in the form of jamming, spoofing, or anti-satellite warfare.
It delves into what we in the engineering game call ‘FM’ – Freakin’ Magic. As the late great Arthur C. Clarke once said, “Any sufficiently advanced technology is indistinguishable from magic.”