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Pocket Radar, Sports Radar Users, Cosine Angle Error

Dec 11, 2010
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With the availability of affordable high quality Doppler radar equipment, I see on forums and at ball fields that a lot of users don’t understand how to use them well. I also see a lot of misunderstanding of how it works.

Handheld radar units are most accurate when the ball is moving directly toward or away from the handheld unit. This is true of all makes and models of hand held radar.

Here is an excellent illustration of how to best use your radar. It also has a chart that shows the differences in readout display if you are not directly in line with the moving object. Note that the error in readout is ALWAYS lower than the actual speed of the object.

This information is from the owners manual of the Stalker Pro II sports radar. It can be found at Stalkerradar.com

Again, cosine effect applies to all all handheld radar units, no matter the manufacturer.

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Dec 11, 2010
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Reposted for everyone that is taking advantage of the pocket radar Black Friday sale.

Do yourself a favor and understand what Cosine Angle Error is.

Understand that dopplar radar provides a minimum speed of a moving object. The most accurate readings (highest) are obtained when the object is traveling directly toward or away from the radar unit. If you are to the left or right or above the trajectory of the moving object, the reading will be lower than the actual speed of the moving object.

When you are in stadium seating behind the catcher is when “above” may be important.
 
Oct 4, 2018
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I'm glad to see that being off-center makes the speed readings slower. :D

Can you imagine if they made it faster? Hey, my DD was pitching 77 yesterday!!!!
 
Feb 15, 2017
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I have done quite a bit of “testing” over the last few years with my PR and a borrowed PR and this is about the range of what I would see...6-7’ left or right of the pitch line usually is 2-3mph off and 10’ left or right is about 4-5 mph off. Almost like clockwork...I would run one and my DW would run the other and compare. Nothing mesmerizing about it when you understand how the technology works.

Now....never been “above that line” until I went to a Texas/OU game and sat dead center home plate top row in front of the press box....right next to an OU staffer (baseball player grad student) running a PR and recording all the data. Of course I chatted him up and learned all kinds of stuff. He was consistently getting readings in the low 60s. Of course my brain said “we are probably 15-18’ above field level....I wonder if my left/right study holds true”. And then I thought about all the crazy readings you on TV sometimes....so I asked and he wouldn’t say. LOL
 
Dec 11, 2010
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Yep, cosine error applies in that situation. Think of the ball being in the center of a cone- every inch or foot you get closer to the outside of the cone effects the measured speed. It’s pretty likely they are correcting for cosine error- At least I would hope so.

He may have not known that they correct it. His job is probably to sit in Seat 22A, push the button and write, lol
 
Feb 15, 2017
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The gist of what I could get out of him was that someone else was charting what was called and where it went and then they overlaid his speeds and they were mainly looking for how consistent the pitchers were from a speed perspective as the game went along. That’s that “behind the curtain” stuff :)
 
Jul 27, 2015
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I have done quite a bit of “testing” over the last few years with my PR and a borrowed PR and this is about the range of what I would see...6-7’ left or right of the pitch line usually is 2-3mph off and 10’ left or right is about 4-5 mph off. Almost like clockwork...I would run one and my DW would run the other and compare. Nothing mesmerizing about it when you understand how the technology works.
Having two guns would definitely give you solid evidence at any given field. If the backstop is not too deep, and I am maybe 10 feet right or left, I add 1-2 mph to the speeds. Not even close to being scientific, and based on what you wrote and the chart posted, I am being too conservative.

Ha! Who ever heard of a pitcher's dad being too conservative on speeds? Actually, I only count my daughter's speed on what the gun says (no adding due to angles) and only if the batter does not swing. So I am getting the actual number.

I used to get her speeds all game long. Then when she got older and coaches started showing up at games, I stopped sitting behind home and went an entire season without getting any speeds. I was very pleasantly surprised this past spring at her speeds in our scrimmages.
 
Last edited:
Nov 18, 2015
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Sorry for the pseudo-hijack - but how does the gun tell the difference b/w ball speed and bat speed? Is it just reporting the last moving object recorded? I'd love to get a PR for both pitching and hitting (EV), just wondering how to read it when there's a pitched ball, swinging bat, and a batted ball all occurring within a split second.
 
Oct 26, 2019
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Sorry for the pseudo-hijack - but how does the gun tell the difference b/w ball speed and bat speed? Is it just reporting the last moving object recorded? I'd love to get a PR for both pitching and hitting (EV), just wondering how to read it when there's a pitched ball, swinging bat, and a batted ball all occurring within a split second.
I could be wrong but I believe it gives the highest speed of the three variables you mentioned in that equation. Which ever one of the three is highest
 
May 15, 2008
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Cape Cod Mass.
When you are in stadium seating behind the catcher is when “above” may be important.
As discussed in another thread being higher up when behind the backstop may give a higher reading than being at ground level due to the fact that a softball pitcher launches the ball at a slight upward trajectory and the radar measures the highest speed which is right out of the hand.
 
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