If you love maps, really excellent long-scroll page with loads of maps and their history.
Henry collected geographic information from anyone he could, assembling a task force of Arab scholars, Jewish merchants, and Dutch, Scandinavian, German, and Italian sailors to produce increasingly accurate maps based on geography rather than myths and legends. […]
Although he did not draw charts—he left that task to academics—Ahmad ibn Mājid published multiple books that aided navigation. Arab navigators relied on his detailed descriptions of routes as well as on his advice about how to use the altitude of the North Star to determine latitude.