I have a map chip in my GPS/fish finder (Navionics Hot Map Premium -West). Unfortunately, most of the rivers and reservoirs in Idaho don't have detailed maps. If you go to the Navionics website and look at details on the map chips they will list what bodies of water have detailed maps are on each chip; if a body of water isn't listed, it will only have the basic map. The only local lake that I have fished with a detailed map is Cascade Reservoir. If you fish in Oregon, Washington or California you will find more waters with detailed maps.