I was recently driving in the southwest, cruising along long stretches of highway that get no FM radio reception. Usually we need to bring CDs or hook up the iPhone to the car, but we were lucky enough to have a rental with SiriusXM, and it was pretty awesome... but I digress.
As a child my dad told me that FM basically only worked along line-of-sight, and not over very long distances, and that's why we had to listen to The Cars on cassette while driving to the Grand Canyon instead of the radio (I kid, Dad. And also I love The Cars still).
So while I was driving along HWY-380 in New Mexico I started to think about the distribution of radio coverage. To cover most of the country there must be thousands of radio towers! Indeed, there are... around 27,000 of them in the US alone! Here's a map of their coverage across the country...
|(click image for high res)|
Super neat! I got the geometries from this handy FCC site. There's a ton of other information available from the FCC, such as radio call-sign. A follow-up project idea: Google or Bing search (whichever API is easier to use) every ratio station in this database (using call sign and city name) and categorize the station's genre based on the results. You could then use Google Maps to chart a road trip, and these coverage maps indexed by genre to determine optimal radio station choices along the way!
On the one hand, this is largely a population density map, with some geography mixed in showing some mountains in the contours. However, there's a more gridded layout along the East coast and in the mid west, providing almost uniform coverage of FM service.
Also, see if you can spot the radio-quiet region around the Green Bank radio telescope!
And just because it's kind of neat, here's Hawaii's radio coverage. Some of the stations only cover one island (it would have been better if I drew the islands... hmm), and you can see on the Big Island (bottom right) coverage holes near those famous big mountains they have!
I also made the figure for Alaska, but it was very sparse. It turns out (not surprisingly) the place in the country with the worst radio coverage per square mile is absolutely Alaska... and that's OK. We should build radio telescopes there.
FYI I put the simple code for this map up on github