50 feet above and 200 feet away? It's the same reduction that I showed for 25 feet above and 100 feet away: 3% low. To compare to BOF's numbers, this is a 14 degree angle.
Here I have assumed that 200 feet away means 200 feet horizontally; if you meant 200 feet on a direct line from the gun to the pitcher, then the gun would read 3.18% low. I personally find it easier to estimate horizontal and vertical distances.
Most Windows computers have a calculator program in Accessories; if you click on View and select Scientific, you can enter an angle in degrees, and click cos. Since you probably don't have a protractor in your pocket, you can estimate the feet above or to the side, estimate the feet away, and follow the following example using 50 feet and 200 feet and a gun reading of 81mph:
50/200 -->0.25
click Inv check box
click tan -->14.036 (this is the angle in degrees)
click cos -->0.9701
click 1/x -->1.03077
click * (or type *, also known as capital 8
)
type in 81
click = -->83.49 (or press the enter key)
So an indicated 81 results from an actual 83.5mph pitch if the gun is 200 feet away and 50 feet above, or any other distances which give the ratio 0.25.
Want to quickly approximate how much to multiply the reading by?
Take, for this example, 0.25, square it (0.0625) and divide by 2 (about 0.03). So add about 3% of reading to the reading to get the actual speed.