If one would like reference their map while on the water, what's the best way? Just open her up on the knees? How do you like to store your maps. I know they have special tubes. Would a homemade piece of PVC work?

folded up and stuck into a map case designed for that purpose (gunwhale straps) with a clear window to view the secion of the map in use. In a pinch you can use a large ziplock bag for this.

At most outfitters you can purchase a palstic bag that the map fits into after being folded... I keep my map in the bag showing the area I am going to, and keep it on the bottom of the canoe between my feet as I paddle, where all I have to do is look down to see where I am going, or pick it up for quick reference. At portages, I just fold it up and stick it in my pocket, and take it out on the other side. You can also do as suggested above and buy a thwart map bag to use...

Bruce

I'll put my plug in for a thwart bag with map pouch attached. I fold the map, so the area I'm in shows through the window and all I have to do is take a glance while I'm paddling. Of course, this only works well for the stern paddler. I keep my camera, binocs, bug dope, hat, etc in the thwart bag where it's handy, and the bag stays attached to the thwart during portages, so it never gets misplaced!
Hope you have a great trip!

I keep my maps in a seal line map case which is about 12"x14". I fold the map so I have maximum coverage showing. I then clip a carabiner to one of the D rings on the case. I had my fanny pack modified to use as a thwart bag and clip the map to that. The map is always ready and wont blow out of the canoe in the wind. In the case I also keep my compass, a mechanical pencil, the BWCAW permit, and a string with mileage markings on it. To store the maps at home I just use PVC tubes with caps fitted to the ends.

I just fold it properly in a ziplock bag to view as Arkansas mentioned. The map cases are $15-20, ziplock is virtually free, but it dosent snap so conveniontly to the canoe.