There is a whole other approach you can take.  If you have a route planned in advance, make a copy of various sections of the map along the route using plain paper.  It can be one map per day or mutliple maps per day.  Get a cheap zip-lock waterproof case and each morning put the day's map(s) in that case.  At the end of the day, put them in the campfire.  All you other day's maps and your "real" map stay dry and protected in your waterproof pack.