Google Maps has more uses other than just providing you with general directions. You can measure distances and areas on the map with it. You can only do this on website though, as the app doesn't support it yet.
You can go to :
Go to Master of Irrigation Website:
to get your yard or plant's area data.
After you get the field area of farm, you can calculation about the lateral to be used or the num of emitters. Online calculation PLS click here.
Or to calculte your farm numer of emitters to be used, go to home page click left down button.