Because GPS navigation devices are so common in today's world, compass navigation is becoming more and more of a 'lost art'. Even reading a simple street map is incomprehensible to a lot of people. It's impossible to argue with the convenience of the GPS- they allow us to navigate very precisely with very little effort, which frees us up to enjoy the journey a little more. They also simplify route planning immensely. But what if they fail?... we'd better have a backup!
GPS could never fail, though, right? Actually, there are a lot of instances in which a GPS might not work...
First, a GPS is an electronic device that requires batteries. We all know that batteries die and electronic devices break. We also know that spare batteries can sometimes be difficult to come by- especially in the short term in a survival situation. A good rule of thumb is to always have a mechanical backup for any critical electronic device. And yes, being able to navigate from point 'A' to point 'B' can be critical.
Next, a number of factors, including topography, terrain, and weather, can cause problems for GPS receivers. Mountains, tall buildings, heavy vegetation, and rainfall can all interfere with the GPS' ability to locate satellites. Murphy's Law tells us these things will be a problem just about the time we really need to know where we are.
Finally, there's the less likely (but still very real) possibility that the entire GPS satellite system could become unavailable or unreliable due to some sort of crisis or attack. Here's an excerpt from a paper written by the scientists at Los Alamos that points out an interesting vulnerability in the GPS system:
The Vulnerability Assessment Team at Los Alamos National Laboratory has demonstrated the ease with which civilian GPS spoofing attacks can be implemented. This spoofing is most easily accomplished by using a GPS satellite simulator. Such simulators are uncontrolled and widely available. To conduct the spoofing attack, an adversary broadcasts a fake GPS signal with a higher signal strength than the true signal. The GPS receiver believes that the fake signal is actually the true GPS signal from space and ignores the true signal. The receiver then proceeds to calculate erroneous position or time information based on this false signal.
The report also points out that GPS signals can be easily blocked or jammed. Other reports have warned that orbiting GPS satellites may be easy targets for enemy states like Iran or North Korea. Some steps have been taken to harden those satellites but, because of the enormous expense involved, those steps do not appear to be enough to actually protect the system.
The bottom line: use and enjoy GPS technology to get around, but don't become overly reliant on it. Take the time to learn to navigate with a map and compass (and to teach your kids or loved ones). If your mentality is "plan for the worst, hope for the best", then owning a good quality compass and knowing how to use it is an absolute must.