Quick question for everyone. I'm trying to calculate my daughter's launch angles. She's a really good hitter, but needs just a bit extra to get it over the fence.

Im just curious how you calculate launch angles. I have been filming her high school at bats. From the first base side. Then I have been pulling up those videos on my tablet and using my protractor on the screen. My problem is I don't know where to place the vertex of the protractor. Is it on home plate or her bat?