Trying to navigate in winter back country can be extremely difficult because of a variety of hazards and challenges: avalanches, snow drifts, weather changes, temperature changes and whiteouts. In addition to possessing a map, compass and altimeter skills, it pays to understand a few methods of snow navigation when traveling by foot.
Handrails are large, visible parts of the natural landscape you can use as visual guides, assuming you can make them out and they run in the correct direction. Examples include following the base of a mountain toward your destination or following a river home. When you can't see anything else, use what nature has provided.
To increase the accuracy of compass bearings and ensure you stay on the correct path, use a partner to extend the travel line. Have your partner hike to the limit of your visibility or attach a rope to your partner and have him walk to rope's end. After finding the appropriate bearing with your map and compass, move your partner until he is aligned with the bearing. Hike to him and repeat this process, ensuring you are traveling in the correct direction.
Aiming off is a technique whereby you purposefully aim to the left or right of your destination. If you are traveling toward a cabin that is along a road, aim not directly at the cabin but to the right of the cabin. This way you know that when you reach the road, you will need to turn left to make your way to the cabin. If you aim directly for it and are off by a few degrees, you may miss it and not know which direction to travel along the road.
When you can't see very far and can't identify the type of terrain you are about to travel into, you can use a rock or other contrasting object to identify dangers. Toss the rock directly in front of you, and you'll be able to better see or hear what is ahead. This method can help you identify hazards such as deep snow drifts and drop-offs.
In many instances, it's better to turn back than continue traveling ahead. You have a better idea of what's behind you and can retrace your route to your starting point. You can also follow your tracks home, assuming they haven't been filled in. To increase your chances, poke deep holes in the snow with your ski/trekking poles as you trek. These holes will take a long time to fill in and will help you to identify your route back.