Its seems dogging started in the United Kingdom, but it is spreading very quickly around the world. I did some research and found the following stuff:
"Dogging is most often practiced in cars at rural parks, lover's lanes and superstore parking lots. The term dogging has a number of suggested origins, but it probably refers to the "walking the dog" excuse proffered to spouses for an evening's absence."
"At the meet, cell phones and text messages are used to confirm meeting places and, crucially, identities. Cameras and videophones are increasingly used to record what goes on."
Found that and alot more in the Wired News
web site here
Found also a site where people arrange the meetings for dogging .... check it out here
Best of all, is the site Dogging Uncovered
, that have some videos that people took on scene, when this dogging events happens. You must check this amazing stuff here