Julia Turner has an excellent article in Slate about hand-drawn maps:
Homemade maps also play with scale in fascinating ways. Paul Stiff, a professor of information design who’s been collecting hand-drawn maps for decades, reviewed all the submitted maps for Slate, and he was intrigued by the one below, which was drawn by an Australian architect to direct his daughter from Brisbane to his farm. Stiff notes: “If you compare this with a topographical map, you’ll see that he’s compressed the scale astonishingly.” There’s less detail closer to home, where roads are familiar, Stiff says, “but the scale expands the nearer we get to the destination because we need more information in places that are new to us.”
Good hand-drawn maps do more than edit out useless details. They often ignore the mapmaking convention that puts north at the top.
Handmade maps also tend toward straight lines and right angles, a phenomenon spatial psychologists refer to as “rectilinear normalization.” The world is full of squiggly roads that intersect at oblique angles. When we envision space, though, we tend to reduce such complexities to relatively simple geometric forms.
[H]omemade maps can be better than professional ones at eliminating extraneous detail, playing with scale, simplifying complex forms, and mapping remote terrain or interiors. Indeed, some computer scientists have examined whether professional route-mapping algorithms could produce maps more like the ones we draw. MacArthur grant winner Maneesh Agrawala developed software called Line Drive that works along these lines, making computer maps more legible by distorting scale and straightening out bendy roads. Like Paul Stiff, Agrawala studies information display, and he became interested in Web-based driving directions when he noticed the limitations of their maps: “They almost never produce a map that I can actually use to get to the destination,” Agrawala told me. “Really the text directions are what I end up using.”