Final answer:
When you cannot find your next checkpoint on a cross-country trip, stop and assess your situation, retrace your steps, use maps, and if needed, seek help while ensuring your safety.
Step-by-step explanation:
On a cross-country trip, if you can't find your next checkpoint, the first thing to do is to stop and assess your situation. It is important not to continue traveling in the wrong direction, as this can take you further off course. Instead, you should retrace your steps to the last known location where you were certain of your position and re-evaluate your navigation. Utilize any maps or navigation equipment you have to pinpoint your current location. If you have planned your route properly, you might have noted distinct landmarks or features that can help you establish where you are.
Following the idea from the references, you could also look for a known distance on a map, such as an athletics track, to help you recalibrate your sense of distance. Remember to communicate clearly with your companions, if any, about the direction and distance to your intended destination, just as you would inform a friend about the location of a fishing hole concerning your campsite by giving both the distance and the direction.
Finally, if you are still unable to locate your checkpoint, it's wise to seek help or contact local emergency services if necessary, especially if supplies are low or if you're in a potentially dangerous environment. Safety should always be your top priority.