The end result of this simple project is a 100% plastic map that is thinner, lighter, and more durable than paper.
Sure, plastic paper can be purchased for printing water resistant maps however, it is expensive, and usually thicker and stiffer than regular paper; making it difficult to fold into a pocket sized, ready reference.
This process produces a map that is only slightly thicker than a garbage bag; that is waterproof, and best of all, can be folded (or crumpled) without damage for stuffing in a pocket.
Step 1: Size and Weight Matters
Nice abstract art but, useless for orienteering.
I like to print my own maps of an area when we go hiking. A trail map, and maybe a topographical (Topo) map, and a road map for directions to the trail head or pick-up point.
The approach used for years, to keep hiking maps from the elements involved storing them in a zip top plastic bag. Folded into quarters, it looks like the map on the left below. It keeps maps dry, however, the folded baggie only seems to fit in the square shaped pockets of cargo pants, and eventually, the folding and unfolding takes its toll on the bag and the paper inside.
Also, There is always a chance the maps will get wet every time the bag is opened. And many times, the bag has to be opened to shuffle through multiple pages for various sections of the trail.
For the most part, this method works, and I will probably continue to carry master maps in this fashion. But, sometimes, especially when traveling in familiar areas, all that is needed is a quick glance at a map to confirm the trail you want is to the left or right ahead.
This is where this Instructables map technique excels... A ready reference thin enough to be stuffed in a pocket, durable enough to survive multiple crumpling and best of all...weatherproof.
It is important to understand the limitations of this process.
Plastic film shrinks when heated so, the map scale will no longer be correct (i.e. a 1/4 inch will no longer equal a mile, etc.)
The fidelity of fine map details may be difficult to discern. Printer ink does not absorb into the plastic film so, the surface tension of the ink will will blur small text and fine details.
Despite these drawbacks, this process will produce a reusable map suitable to tuck in a shirt pocket for reference on the trail in the worst weather, or as a very compact emergency back-up map tucked away in a survival kit.