In any hike you can not do without maps, especially in the mountain. What are the main criteria in the selection of topographic (based on photographs) map?
Let us start with the image quality. The map should be easy in the first place to find ridges and valleys. Besides the already mentioned high-altitude lines, helps a variety of colors, shades, brightness. A good way to check the map is try to make a route yourself through any ridge and try to assess climb rate, slope angles, landscape type, and then compare with the real data.
So as the glaciers in the Alps is being actualised during melting, the date of map creation is important too. Because after the melting of the glacier beneath it can appear a difficult rocky relief for which the group may not be ready. That is why maps of the General Staff 80's and 90's of the last century is not recommended as a basic for a hike in the Alps. On the older map under a glacier can be hidden anything, and what is it, you will find out just by coming to the place, and you probably will non be glad to this. Than the map is newer , the less you will find surprises.
On the territory of the Alps there are the boundaries of states, which is also a problem in finding maps. Most maps are accented on one state, and they provide information almost without leaving the boundaries of the state. So you have to look for maps of different publishers and match them so that they are quite complementary. Existing project "Alps without Borders", which aims at solving the problem, but its geographical coverage is not so great.