Radar Gun and Speed July 28 2016, 1 Comment

Darryl to Coach Arnald Swift

I was holding the radar gun (Striker (sic) STALKER but I don’t know the model number) for my nephew. Being a physicist rather than knowing anything useful about baseball, I noticed it read to one decimal point from which I inferred it was measuring speed to the nearest 0.01 mile per hour and the rounding to the nearest 0.1 mile per hour. I asked him if he knew what the accuracy of the gun was and its precision and he didn’t so my 1st question is what is the accuracy and precision of your guns. My second question is how close to parallel to the balls flight path must the gun be pointed before it begins to reads wrong due to the misalignment and does anyone ever worry about that? I think he is very happy with the gun, I was just wondering about these things so thought I would ask.


I apologize for not getting back to you with my thoughts and comments on your letter, somewhere other this got send it to spam and I just discovered it today I had no means or way meant to slight you because the question is interesting. I taught math and computers and so I also think a little bit like yourself.

As far as the accuracy of the guns even the most accurate of guns don't actually read in the hundreds of a mile, it's common to see 10th of a mile but when we use the professional guns made by Staker (most popular among professionals) they read in miles per hour not hundredth or tenths from a radar gun on a baseball or any other sports ball.  

A radar gun reads in a direct line best so when doing baseball to set up behind the pitcher or behind the catcher in a straight line to get the absolute most accurate reading. Then also remember that the radar field measures about 30 feet away from the location where the ball started or stopped. It's interesting to note that the speed of the ball out of the hand at 30 feet is faster than the ball at the catcher 30 feet away into his glove. Simple physics in a way the ball is actually slowing down on its way to the plate and perception but it is a little bit slower as it reaches the plate. For baseball people the most accurate is at the plate because that's where the batter has to hit it.

Now the angle of reading the flight of the ball is ideally 0 to 10° but you can get relatively accurate readings up to about 20° of variance the good guns have the ability to do some math internally and get an accurate reading from off a direct line.   And one other factor that you did mention is how far away there are some smaller versions, cheaper versions, that need to be within about 20 to 30 feet to have any accuracy at all then the professional type guns are accurate through screens, batting cages, that kind of material from up to 300 feet. I've always found it interesting that the manufacturers of police radars, have the same exact radar guns available to the sporting industry. They just change the recording devices to meet the needs.

Hope this helps in your thoughts and your curiosity and I certainly appreciate your interest and sorry about the time lapse.

Coach Arnald Swift BATCO

Stalker Radar Gun Sport 2