The GPS data from a cell phone is not accurate enough to create the map of red dots that Captain Gates shows the team. Not only would the data be too vague to show the victims locations, it would also have been unable to show their movements to the degree shown.
Both at the beginning and when Castle is going over the crime later, the cameraman says 'let's roll this puppy,' and it takes a few seconds for Leeann West to reply 'Roger that.' Yet when Castle is watching a news report, she says it almost immediately.