[Shep]

A magnetic compass will be affected by close proximity to alkaline batteries such as Duracells. Storage in a backpack next to a flashlight and GPS will be enough to permanently affect the polarity of the compass needle/pointer.

To see if your electronic gizmos are affecting your compass, try the simple experiment of moving your flashlight, GPS, etc. close to the compass. If the needle moves, you've found the culprit.

If you're trying to find your way in low light or the dark, holding the light close to the map or compass will be enough to distort the compass reading by a large amount. That deviation will not always be the same, so it isn't possible to compensate for that "interference" alone.

In compass navigation it's useful to remember the nemonic for accuracy, "True Virgins Make Dull Companions": True, Variation, (from the compass rose on the map) Deviation, (from nearby metal or other interference) and Compass (reading).