OpenStreetMap
Maps, their lineage, and the intrigue of invisible roads
Posted by Larry Gilbert on 14 December 2008 in English.I made an interesting discovery while verifying streets near my neighborhood in San Diego. There was about a mile's worth of streets charted in one little area that simply didn't appear in Yahoo's aerial imagery, so I investigated them in person. Turns out they really *aren't* there. I placed a marker to mark the imaginary intersection of Buchanan and Oklahoma Streets, roughly the center of the place where they all appeared before I corrected the map.
In reality, the phantom "streets" traced the contours of little valleys in the canyon by the neighborhood. Some of the streets just extended existing streets far beyond their real length, others (such as the aforementioned Buchanan and Oklahoma) seem to have been made up entirely.
Where did those streets come from? Not sure. But I learned a little more about the history of the data, and that may lend itself to some guesses. I found San Diego's GIS data, and it shows the same phantom streets that were in the TIGER data--so it seems to follow that the TIGER data came from the City of San Diego. A historical note accompanying the data mentions that the it was originally compiled by the local gas and electric utility (SDG&E), then handed over to the city government in 1990.
Maybe the utility company invented those streets to watch out for anyone leaking their data? Or, as my wife suggests, maybe the streets were planned streets that never came into being? or roads that once existed but are gone now? I guess I will have to look up some older maps at the library to solve the mystery.
Discussion
Comment from chillly on 14 December 2008 at 11:12
It could be that the utility company added phantom roads to help monitor their copyright - as you say leaking their data. This addition of imaginary stuff is common, but usually simple small changes that don't affect the usefulness of the map. These are sometimes known as copyright easter eggs.
Comment from LivingWithDragons on 14 December 2008 at 14:14
Or maybe there is some big secret about those roads, like an underground government community of aliens that they don't want the general public to know about!
I wonder if the data has 'infected' any other uses, like population/census information.
Comment from Larry Gilbert on 14 December 2008 at 23:16
(LivingWithDragons) "Or maybe there is some big secret about those roads, like an underground government community of aliens...!"
With San Diego government, it wouldn't surprise me. It might actually explain a few things. :-)
Actually, when I mentioned this to my wife (long-time native), she claims there *did* used to be some underground tunnels for pedestrians here, but they were much closer to Balboa Park--and they were all filled in the 1970s to close them off due to public safety problems.
This further reminds me of underground tunnels in my hometown in Oregon, supposedly connecting various parts of the city with a big, central, underground space--all constructed for Civil Defense use (the whole nuclear-war-preparedness thing of the Cold War days). In present times, I think the tunnels have a more mundane use as home to various utility conduits. When I was a schoolkid in 1980 or 1981, I got to take a classroom tour of the tunnels that connected to our school!
And then there is the historic underground neighborhood that was built in Seattle around the beginning of the 20th century. It is still accessible today for the price of a ticket for the Seattle Underground Tour. (I lived in Seattle for 15 years and never once went on that tour; I'm kicking myself.)
Comment from RichardB on 15 December 2008 at 00:10
Could they be streets which have been removed for redevelopment? I bet some of that TIGER data is pretty old, so wouldn't be out of the question.
I came across a place earlier this year in the UK where an entire area, previously run-down council-owned housing, had been demolished and had all the roads dug up ready for full scale redevelopment.
Comment from Vincent Broman on 13 December 2013 at 20:41
At least in central San Diego, the phantom streets seem to be areas where the city owns or owned the land and had an option of building a street there, but which never (yet) ended up being created. If you check many of them out, they tend to be alley ways or narrow vacant lots.
In a South Park micro mall recently, one store had on display an old map with no date, probably 1930ish, with a fascinating mixture of reality and hopes, like the real Rancho boundary along Boundary St., and the imaginary cluster of streets developing all the canyon bottoms by Hollywood Park.