In the olden days, i.e. the 1990s, there was a practice among mapmakers to intentionally include trap streets on reference maps to protect the copyrighted material. The idea to fabricate a street, or the name, or a feature, implant a pattern… ideally something small enough that it won’t mislead a map user or be noticed at all until the point where it is necessary to prove that someone else copied your proprietary data into your map. They are tricky to use in US court cases ever since a federal court ruled that, “the existence, or non-existence, of a road is a non-copyrightable fact.”
Although they show up as artifacts in online maps, the practice seems archaic in the current era, where lines drawn on paper maps have been converted to digital file formats, usually though a painstaking manual process of georeferencing, tracing, and/or orthorectifying. Once geographic information becomes “data”, the manual process of cleaning and maintaining it becomes an incidental rather than central part of map-making, a tedious and unrewarding process left to “data monkeys”, “interns” and “quality assurance” teams.
Trap streets seem romantic in the era of plain old errata which, once they have been integrated into a geographic data set, and copied, distributed, and reproduced, are near-impossible to completely eradicate.
Here is something I like to think of as a trap street, even though it is really an erratum: Sunset Reservoir!
Sunset Reservoir: Google Maps
Looks like an awesome natural space suitable for dog walking and sunbathing. Actually, it is an underground and completely enclosed… reservoir.
Sunset Reservoir: Google Maps & Google Street View
I think I know exactly where this error comes from, because when I used to work for the City/County of San Francisco, I used to warn colleagues about the “water bodies” shapefile that was passed around interdepartmentally — in addition to Lake Merced and the lakes in Golden Gate Park, it contained this reservoir, most likely because it was originally created by the Department of Public Works to track the water resources of the city, not the locations of urban lakes. Should I press the “Report a Problem” button and let Google know?
They are in good company, I upgraded to Mavericks this weekend, so I can say definitively. It’s also not fixed yet in Apple Maps:
And incidentally, here’s an argument for manual data creation/curation. Open Street Map:
(originally published at mizmay.com on 2/9/2014)