Off roaders have graduated from compass and maps to GPS. Technology provides easy, convenient storage of many maps in a small space. Coupled with other features, GPS is a must have accessory in any equipped 4x4. But, there is no substitute for a backup and that backup should be a good quality compass. In reality, having two compasses is a preferred option.
Why two compasses? Should the occasion arise where you are without GPS and dependent on a compass, it is possible to get yourself turned around. You look at the compass and your brain will tell you the compass must be wrong. Then is when you can really become lost. But, pull out at the second compass and check your heading. While one compass could be wrong, or you believe it to be wrong, you’re more likely to believe two compasses aren’t lying.
Source: Bug out bag essentials - Compass