This is the second question in my Arctic Airships series of questions. The first one is Arctic Airships, Part 1 - Generating Electricity.
The setting is outlined in Part 1, but I'll rehash the premise here.
An Earth-like planet plunged into an ice age roughly 2,000 years prior to the story. The ice sheets extend to a latitude of about 50 degrees above and below the equator, though I this story (so far) takes place in the planet's Northern Hemisphere. At a latitude of about 67 degrees north are a series of ten or so small villages, each with a population of 500 people.
The technology is roughly that of the late Victorian era - so no automobiles. In fact, there is no clear boundary between icy land and frozen-over water, and it would be extremely dangerous to travel overland in any way. Submarines have not been developed, nor have airplanes; a lack of fossil fuels means that internal combustion engines are nonexistent.
Some of our heroes have gone rogue in an airship to see what lies beyond the Rocky-Mountains-esque mountain range to the south of their land. To their surprise, there is nothing but more ice as far as the eye can see. Yet they are brave, and they are determined to carry on, risking life and limb to go where nobody has gone before and returned to tell the tale.
The problem is, they forgot to bring a compass - or, rather, the engineer dropped it shortly after takeoff. They have nothing that they can use to create a new one. The crew decides to use the Sun for navigation; unfortunately, they're in the middle of winter, where the days are extremely short, if existent at all. It seems like they won't be able to find their way.
They could just go straight, and that is in fact their plan, but a storm hits, and they lose their bearings.
How can they figure out which direction they are going? They have only the supplies on board a typical airship - maintenance tools for the engines (e.g. wrenches, screwdrivers, drills, etc.), food, paper and pencils, some clean clothes and sheets, and various personal items.
I should add that I'd like to avoid extended discussion; please use general chat or a separate chat room created for Part 1.