colonial powers had to know about the places, their climate,crops,minerals resources and about the people living there
they sent scientific expeditions consisting of map makers and other to explore the different parts of the world and prepare maps
these teams found their way in to interior of continents crossing mountains,desrts and river fighting with local people to get the necessary information
this information and the maps enabled the colonial powers to established their rule over these areas and also exploit their resoruces
and due to maps the military can know the places where the strangers attacking the place and they can plan before the fight what they have to do.etc.....
by these ways maps are useful