Here is a non-technical , partial description , of a
Cell Phone Ping
--- Ping is actually an old word we use to describe radar signals sent out and received
--- Your cell phone knows where it is at all times (generally speaking)
--- Your cell phone is "in touch" with (most of) the towers in the area , and knows which one is closest
--- Watch the signal-strength bar on your phone , it gets stronger as you approach a tower and weaker as you leave
--- In order for the phone to know where it is (where the towers are) it sends and receives pings (signals)
Here is another way to look at it , you and your friend are sitting side by side on your sofa , you dial your friend and her phone rings in her pocket.
Tomorrow your friend flies to Paris France and you dial her number and her phone rings in her pocket. How did the phone know she was in Paris or in your house ??? ... it does so by staying in touch (sending pings) back and forth to various towers .
And if it contacts two or more towers we can
triangulate the lines of signal and pin point the location (see below) .
It is not "quite as easy as that" ... often permission or a search warrant is required , a bunch of computer content has to be downloaded and searched , and is only done in serious situations , so when police say they have obtained "a production order" from the phone company , that is what they are talking about
In real life it does not always work that precisely , there are still many places that have no towers at all , some places only have one tower which will know it received a ping but not which direction it came from. But investigators can use that info too .... if your last signal was in Winnipeg MB , then nothing for 7 hours , then a ping to a Thompson MB tower , it indicates you went north on highway #6 , or at least your phone did.
A beautiful Hollywood Actress is the one who figured out whether your phone is in your living room or Paris France . More about that in a minute.
(Most likely)
Thelma's phone was in contact with two or more towers in North East Winnipeg , and if her phone has GPS capability it can show the last ping location
within a few feet
.