In 2010, the U.S. Department of Defense spent a lot of money developing interference-resistant alternatives or backups to GPS (depending on who you talk to). The best candidate is the improved INS, which has been around for almost a century but has become smaller, cheaper and more reliable since the 1960s, just like electronics. Basically, the INS uses three gyroscopes and three accelerometers to constantly measure changes in direction and changes in speed. With this, the INS will always know where it is relative to its original starting point (initially available via undisturbed GPS or older means). Microins devices have long been used as back-up devices for GPS-guided weapons. But while GPS guidance can land a bomb or missile within 10 meters (32 feet) of a target, the INS can only achieve an accuracy of 30 meters. GPS also has the advantage of not having to enter its exact location once the INS is powered on. On the plus side, this means that Instagram can't be interfered with or tricked. These tiny gyroscopes and accelerometers have become standard on many smartphones and can detect not only direction but also motion. Smartphone manufacturers' use of this technology has led to cheaper, more reliable designs that have proven useful for military INS backups of GPS.
After 2010, researchers in the United States created new concepts and techniques that could significantly improve the accuracy and cost of current INS. In 2013, prototypes proved they could be almost as accurate as GPS, and almost as small. Cost is always a factor, with new INS always costing more than 10 times as much as GPS. But it's a big improvement over what was previously available. The new INS can now be used to monitor GPS and alert operators that their GPS is faulty or blocked. The new INS is also suitable for some fast missiles that often lose their GPS signal when maneuvering. Another urgent task for INS is to alert users that their GPS is being spoofed (sending a false signal that lures users). So even with the ability of jamming technology to keep up with jamming technology, there is still a need for new INS. This has led to smaller, cheaper and more accurate INS systems. Outside of airlines and commercial shipping, these new INS systems don't have much of a mass market, because for most consumers, GPS is reliable enough to keep INS devices out of the big market. But the demand from airlines, shipping companies and the military is huge. However, the technology remains popular in smartphones and other consumer products, but unlike INS.
Many Department of Defense navigation and electronics experts believe that the current anti-jamming work is enough for military GPS to continue to be used, but the new INS technology has caused widespread concern around the world. The Army is always appreciated as a reserve force because when equipment fails in combat, it is literally a matter of life and death. At the same time, the US is building and testing more compact GPS anti-jamming systems for small drones (as small as 200 kg /440 LBS). It's part of a plan to equip all U.S. drones, even the smallest ones, with more secure GPS. While all UAVs can be "piloted" by an operator, GPS makes it easier for operators to know exactly where their UAVs are at all times, and sometimes UAVs are programmed to simply patrol between a series of GPS coordinates. If the GPS crashes or malfunctions, the operator can often use the video feed to look for landmarks on the ground and return the drone to where it can be seen and landed.
Although the U.S. military has not yet encountered battlefield GPS interference, if any, the threat is present. Currently, the US military can experience this in Ukraine (where NATO countries have advisers and military observers) and in Syria. The jamming technique has also been used in Iraq and Afghanistan. Until now, the most tangible evidence has come from North Korea, which has long manufactured, sold and used its own GPS signal jammers. In 2012, North Korea attacked South Korea with a widespread GPS jamming campaign. The disruption began in late April and lasted for more than two weeks. It takes less to confirm that the signal originated in North Korea and was primarily sent to the South Korean capital (Seoul). The interference had little effect inside the city (ground jamming signals were blocked by buildings and hills) and could only be seen by the hundreds of aircraft taking off and landing from the local airport and more than a hundred ships operating at sea. In all of these cases, ships and aircraft have backup navigation systems that are activated when GPS becomes unreliable. That's how navigation systems are designed, especially those that rely on external (satellite) signals. Inside the city (where ground jamming signals are blocked by buildings and hills), only the hundreds of aircraft taking off and landing from the local airport and more than a hundred ships operating at sea can be seen.