Topographic Maps aren't cheap. Well, in most cases they aren't free. Protecting your map is protecting an investment that will give years of use. This instructable will demonstrate (and remind myself) how to fold a map to fit in quart sized ziplocks. I prefer the quart size, so I can put the map in a small accessible pocket on my backpack. The trade off is that that puts more creases in the map. Creases serve 2 purposes. They wear out the map in that spot quicker, but more importantly, if your creases are accurate to the edge, they provide north/south and east/west lines.
This instructable is for 1:24k scale 7.5 minute quadrangles in the U.S. For other countries and maps, you may need to experiment a little.
Step 1: Align the First Fold
The first fold is the most important. If the first fold is not aligned, you'll get misaligned north south creases. Lay the map face up and fold along the vertical axis. You should then have half a map and the white side should be visible. Line up the edges well and crease.
Step 2: Fold the Sides Back
Take the top layer on the map and fold vertically again toward the crease. Flip the map over and do it again on the other side. What this will do is put the titles that are on the top right and bottom right on the outside of the finished product, making it easy to find the map you want. Make sure the titles are facing you.
Step 3: First Horizontal Fold
With the titles facing you, fold the map horizontally so they are no longer visible. Make sure you get a good east-west fold. Match the folds together at the bottom of the map.
Step 4: Finish Folding
Fold the top layers to the crease like you did in step 2. Repeat for both sides. If you did things well, you should see the map title on both sides, making it easy to grab the one you want.
Step 5: The "Waterproofing"
Put the map in the bag and seal it up. You'll notice it acts more like an inflatable pool toy than a bag. My Dad came up with a genius way to solve the pool toy problem.
Put the edge of the ziplock in between your canine teeth, bite down, and pull out. If you're feeling really adventurous, get a pair of scissors and cut a small slit in one side of the bag. The hole is small enough that air gets out, but unless I really use it as a pool toy, water doesn't get in. I've been doing it this way for years, and I haven't ruined a single map in inclement weather. If you're worried about the waterproofing, don't cut the hole.