The AP estimated the speed of the train by______.

Here is a searing piece of video and some remarkable journalism as a train derails horribly in Spain, killing at least 78 people. The Associated Press took the video and went to work. A video producer advanced it frame by frame.(25)The AP used a time stamp on the video to calculate the train’s speed. One estimate: 89 to 119 miles an hour: using a different technique, 96 to 112.(26)The posted speed limit is 50 miles an hour. In less than two hours, the AP went from video to story, providing vital information.