Some clever marketers have come up with an idea for putting QR codes on the tops of buildings such that the code can be seen on Google Maps and Google Earth satellite photos.

The concept is to essentially leverage rooftops as ad space that then becomes part of the photographic record (for free) on Google’s popular mapping service.

Creating the giant QR codes and putting them on the buildings, however, is not free, with one company charging about $8,500 to do so.