Wifi Networks between Dublin and Sligo

I was on the train from Dublin to Sligo, with a laptop, a power socket, and boredom, so I made this:

(Click the image for a high-resolution version)

The graph shows the number of distinct wireless networks seen in each minute along the journey. The points along the bottom are accurately spaced, I measured when the train arrived at each station (Yes, I was that bored). The leftmost point isn't quite Connelly Station, the train had already pulled out by the time I thought of doing this. The green line shows a smoothed version of the data, so the average number of networks at each point is more obvious. The data were collected by airodump-ng, part of aircrack-ng, parsed with some Perl one-liners and graphed using the excellent MatPlotLib Python graphing library.