Jake Berman, a midtown lawyer, was recently examining the M.T.A. subway map on a wall of the West Fourth Street station, when an elderly tourist asked him how to get to Chelsea. Berman began to relay precise directions; then he stopped. “Funny story,” he said. “I designed a subway map—a competitor that the M.T.A. wants to get rid of. So you’re asking the right dude.”

The funny story begins twelve years ago. Berman, a transplant from San Francisco, was at N.Y.U. Law School. One weekend, he had a date in Brooklyn. After consulting the subway map, he decided to take the B train from West Fourth. “Here I am, waiting like an idiot for half an hour, and there’s no B,” he recalled. “They didn’t have countdown clocks. They didn’t have cell-phone service. The whole thing ends up being a slightly dramatic fiasco.”

Berman gave up on the date; he later learned that the B doesn’t run on weekends, a detail that he couldn’t find on the map. He got so angry that he designed his own map, spending hundreds of hours on it and joining the ranks of New York’s amateur transit cartographers. He has since revised his map and designed some for other cities, and even for science-fiction epics. (He rendered all of “Star Wars” into a diagram.) “Frustration is a great way to become creative,” he said. Two years ago, he discovered that, after he’d posted his New York subway map on Wikipedia, in 2009, someone had begun selling it on Etsy. He wrote in to complain. Then he stole the idea. He listed the map himself, at a starting price of fifty dollars.

Trying to explain the workings of a megacity’s transit system with elegance and accuracy is about as easy as describing the city itself. Some poetry is required. To create the first color-coded subway map for New York, in 1967, transit officials brought in a former rocket scientist, who devised four prototypes; instead of choosing one of them, the officials mashed two together, resulting in a much hated composite. Then came Massimo Vignelli, an Italian designer who drafted a map that was crisp, beautiful, and easy to read, but defiantly indifferent to geography. The map is in the collection of the Museum of Modern Art, but the M.T.A. ditched it after seven years, considering it too abstract.

Today’s official map emerged from the work of a committee, headed by John Tauranac, a writer in the transportation authority’s marketing department who hated the Vignelli design and pursued one that correlated more closely with the actual city. That map, presented in 1979, was celebrated, but over the years it has been repeatedly tinkered with, and has evolved into a visual mess. Last summer, Tauranac petitioned the M.T.A. to hire him to revamp the design. When the agency ignored him, he went to the press, telling the Post, “It’s incumbent on me as a map designer to say, ‘Look, schmuck, you could do a better map, and I could do it for you.’ ” He added, “I wouldn’t say ‘schmuck.’ ”

Berman’s map is suavely graphic, like Vignelli’s, but it also adheres to the city’s geography. He has earned a few thousand dollars selling it online. Last month, though, he got a notice from Etsy, saying that the M.T.A. had ordered the site to stop selling it. Berman got on the phone with an M.T.A. lawyer. “He alleged that I had ripped off the Weekender,” Berman said, referring to an obscure online map that the M.T.A. issued in 2011. He told the M.T.A. that he had created his map years earlier, and that he would not comply with the agency’s order.

Other amateur cartographers sympathized. Eddie Jabbour, the creator of the KickMap, a subway app, told Berman that the M.T.A. had hassled him, too. Even Tauranac, who for decades has been drafting unofficial subway maps, said he was once ordered to desist. “It’s like déjà vu all over again,” he said.

“It’s a very trivial thing to start trouble over,” Berman said. The M.T.A. apparently reached the same conclusion. The agency declined to comment on the Etsy situation, but shortly afterward it withdrew its legal demand. Berman celebrated with a bottle of brandy. “There’s nothing more New York-y than this,” he said. “Everyone sends lots of threats, stomps their feet, but in the end we come to an agreement.” ♦