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Radar Gun Fun, Part 2

Demystifying the Radar Gun: What Leads to Inaccurate Readings?

You just got that brand new, super expensive radar gun. So excited you break it out of the box and head straight to the nearest baseball field. You get there and realize you are getting some weird readings. If you don’t know much about what can cause radar gun errors, this can leave you in a state of confusion. Whether it is a slow reading, inability to get a reading, or “ghost” readings, the cause is usually something that can be explained.

In this second part of the Radar Gun Fun series we will cover common errors, mistakes, and what interference is. The previous blog post discussed what radar is and how it actually works.

Mis-Aiming the “Cone”

The first error is a simple and silly one. Some of you may be thinking “well duh”, but not aiming the cone correctly needs to be talked about. The “cone” is the area of the “frame of capture” of a radar gun. This was one of the topics from the previous article.

Being in front of the pitcher can provide fewer physical obstacles when aiming at release point, but be careful with your tilt.

So, let’s begin with how we want to aim the cone. The ideal spot to cast your cone is from in front of the pitcher. This means you should be standing behind the home plate and the catcher or behind the backstop if it is not too far away. Obviously, it is a little safer behind the backstop, but a net will do just as fine as a safety precaution. If necessary, standing behind the pitcher will work, too. From that spot though, the path of the arm and body can get in the way. Minimizing objects in the way will make it easier for the radar gun to capture the velocity of the baseball. The main goal is to be in a straight line with the path of the ball. Also, from behind the pitcher standing further back will let to cone spread out more and make it easier to aim. We always want the cone to be aimed to capture the ball at release. Air resistance causes the ball to lose velocity very quickly as it travels to home plate so this will allow for finding peak velocity. Once set up in the right position, mis-aiming the cone can still occur.

One way this happens is tilting the radar gun. Even a slight downward tilt can make the cone end up pointing at a spot on the ground in front of the pitcher and not allow you to get the ball at the release point. Usually a downward tilt will come after multiple innings and numerous pitches when your arm is getting tired. Over correcting for this or just simply not paying attention (such as writing down a scouting report) can lead to an upward tilt, though. It is a cone and not a linear line, but this could still lead to picking up the ball sometime after the release point when it may be several MPH slower, because the diameter of the cone is only so big. The same thing can be said for aiming the gun side to side. So, kind of like a real gun, pay attention to where it is aiming as this could cause more complications, such as cosine error.

Cosine Error

Left: Reading with cosine error; Right: The actual reading of the same pitch

I remember being a kid thinking you wanted to be perpendicular to the path of the ball only to learn later in life that this is completely false. Like mentioned above, the radar beam should be in a straight path with the flight of the ball. If the cone is shot out at an angle to the path of the ball, then the radar gun will give a slower reading. So, if a scout can’t sit directly behind home plate and has to sit off center, their readings will be lower than the true speed. This can be accounted for though.

Unfortunately, this involves some math. To get the concept, it involves some trigonometry, but don’t worry, it all simplifies down to an equation. So, armed with the calculator app on a smart phone, anyone can calculate this error provided they know the angles involved.

Measured Speed is what the radar gun shows, Vo is the actual velocity, Alpha is the angle; If you divide measured speed by Cos Alpha you will find actual velocity (Vo)

We discussed above that it is ideal to aim in a straight line with the path of the baseball. When off to the left or right, an angle is created when aiming. That angle correlates to the difference in velocity reading. If you divide the reading from the radar gun by the Cosine of that angle, the resulting number is the actual velocity of the baseball. So, if you are getting a reading of 90 mph while at a 10 degree angle, the actual velocity is about 91 mph. If scouting, it may be difficult to know the exact angle so it may be a guessing game. No matter the angle though, it will always read out slower than the actual velocity. That is because with the radar straight on, the angle is 0 degrees and Cosine of 0 is 1. So, dividing the reading from the gun by Cos(0) yields the same number from the gun. With every increase in degree of angle, Cosine becomes smaller and smaller until it reaches 0 at 90 degrees.

Min and Max Measurement Range

Since radar guns work by sending out radio waves and bouncing them off a moving object. The maximum distance they can make a measurement depends on three things: How much power they put out, how well radio waves reflect off the object, and how low a signal the radar gun can detect. Not all radar guns are created equal. The larger radar guns put out more power and can measure a baseball from up to a few hundred feet away. These are often used by scouts when they want to sit back in the stands at a stadium. The small units like the Pocket Radar are designed more for coaching and training, or scouting on amateur fields and can measure a baseball from up to 120 feet away.

Since a baseball will slow down by around 8 MPH from the pitcher to the catcher, you need to be sure you are well within the maximum range of the radar gun to reach the release point of the ball. If you are using a radar gun with only 120 feet of range but are sitting in the stands at 150 feet away from the pitcher then the ball will not get into the range of the radar gun until it is halfway to the catcher and has slowed down by several MPH. This might make you think you are getting readings that are not accurate when in reality it is because you are too far back.

There is also a minimum distance that the ball needs to travel through the air for the radar gun to get a good reading. This is because it takes time for a radar gun to find the ball and then make enough measurements to get the maximum speed of the ball. If you are throwing or hitting into a net that is only a few feet away, then the ball may only be in the air for a tiny fraction of a second and the radar gun may not be able find the maximum speed. A good rule of thumb would be to make sure there is at least 12 to 15 feet of distance for the ball to be in flight before it contacts anything that would slow it down. This allows for enough time for the radar gun to make all of the necessary measurements to find the maximum release speed or exit speed off the bat. If you think you are seeing low readings, move further away from the net and see if you get better readings.

Frequency Interference

When dealing with microwaves, interference is a problem. This is something that every radar gun can experience. Cell phone towers, other radar guns, and even motors and fans from cooling systems can interfere with the radar gun attempting to get a reading. On top of that metal acts as a mirror, so if there are bleachers beyond the outfield walls, better hope they are made of wood. Even though the microwaves are invisible, they can be influenced by other signals or waves. Taking note of the surroundings is a smart idea before settling in to get some readings.

The surroundings to the field could cause complications when attempting to get radar readings

I experienced some interference heavily at one stadium recently. Not only was the field near a cell phone tower, beyond the outfield was a freeway crossing with cars flying by in the background. This led some funky readings, or what is known as “ghost readings”. This is when you get a random reading without a pitch. Common numbers you might see from cell phone tower interference are 28, 56, 84, and 112. Unfortunately, for me, that day I was trying to measure the velocity of a pitcher around that 84 mark. If you are not working around those numbers, then it can be easy to decipher the difference between the ghost and real readings. A good rule of thumb though, is to never to trust a single radar gun reading. It is fairly easy to tell if you are getting interference. Simply scan the radar beam around the environment when there are no balls in flight and see if you get any readings when you don’t expect to. By aiming in different directions, you can often identify the source of the interference.


There is another aspect of some radar guns that can affect the accuracy of the readings that isn’t necessarily interference. Depending on the technology used inside, some radar guns may need tuning and calibration. A drop or bump could send that calibration out of whack. According to Jeff Passan in his book “The Arm”, there is a scout by the name of Bill “Yogi” Young whose chosen radar is the Stalker Pro II. He sends his gun off every year for re-calibration, never has dropped it, and of course, kept it out of the rain. He took very good care of this radar gun. So, it can be expected that radar gun will perform within its specified accuracy. Not everyone will take that great care of it, but the better it is taken care of the longer it will stay calibrated. This is not true for every radar gun as some, like the Pocket Radar, use newer technology that does not need to be re-calibrated. So, make sure to take note of what your radar gun needs in order to maintain its accuracy.

Comparing Accuracy

Interference, tilt, aiming at an angle, being too far away or too close, not capturing the ball at release; any of these can cause a variance out of the gun’s control. After two blogs explaining the ins and outs of radar guns, controlling these variables is possible. That will allow us to truly compare a few different radar systems. The third part in the series will look at the Stalker Pro II and Sport II, Pocket Radar Smart Coach, and a run of the mill Bushnell radar gun. In this we will compare pitch to pitch and average reliability that will determine which situations each radar is useful and most effective.  We will also include the Diamond Kinetics PitchTracker, which is not a radar gun, but is being used by amateur athletes to measure pitch velocity using a different technology built into the ball.  See you next week with the finale of the Radar Gun Fun series!

Left to Right: Stalker Pro II, Pocket Radar, Stalker Sport II, Diamond Kinetics Pitchtracker, Bushnell


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