It's difficult to find much in-depth information about pings and triangulation. It appears to be very sensitive information for the government and LE, imo, based on what I have found available. I too wish we had a verified expert here at WS!
Here is a snip from an article that is simple and useful, imo.
Cell phone triangulation is a well-known tracking method within the wireless industry, said Michael Barker, an equipment sales manager for Cell-Loc, based in Calgary, Alberta. His company provides tracking services to help people who are incapacitated and unable to dial for help.
"Every time the cell phone is on, it periodically sends a little registration message to the phone company, 'Here I am! Here I am!'" Barker said. That message contains the cell phone's electronic serial number and tells the service provider when the phone has drifted in and out of cell tower range.
Federal agents then easily can get in contact with the cell phone service company and get the location of the nearest cell tower in contact with the activated phone, Barker said.
Law enforcement then can equip agents with devices designed to triangulate the signal and determine its location within about a third of a mile and the direction it was traveling in, Barker said. Handheld equipment for such a search is not sold to the general public, he said.
http://www.wired.com/science/discoveries/news/2002/05/52396