Map Skills Section Assessment 1a. What information sources do mapmakers use? Mapmakers rely on ground surveys, aerial photographs, and satellite images. 1b. What are the advantages and disadvantages of each information source? Satellite images provide the big picture but not all the details, while ground surveys give all the details but not the big picture. 1c. To make a map of small streams in an area of thick vegetation, what source would a mapmaker most likely use? They would use ground surveys so they could see the streams under the vegetation. 2b. Which projection would you use to plan a voyage by ship in a straight line across an ocean? You would use a Mercator map to plan a voyage by ship.