Heat map of cellphones on a single Florida beach during spring break

Poster here. The title is a copy & paste of the tweet, as per HN guidelines. It is the topic of the tweet.

However, cellphones on a Florida beach is not that interesting (well, to me anyway). It's the data displayed to make the point and it's implications that's interesting. The data is (I think) an ad in disguise. It may not have the effect the wanted and be taken down, so I've mirrored it here:

https://drive.google.com/file/d/1ckax1R8pmT1jwpycjP7t8TgDHCO...

Troubling from the privacy aspect...

I'd prefer to see a different visual than a heat map, those just end up looking like population maps. https://xkcd.com/1138/