Distances - Driver

[SingleDigit]

I just got my new ST on their latest promotion and set up a basic sim in my garage. Out of the box I started with a PW and my distances looked good. I worked my way through my bag and noted that my driver was way short. I kept at it knowing that I didn't hit every ball clean. After about 20 shots, my shots barely increased in distance but was still about 40-50 yards short.

I went to WGT to play Pebble and came back to Practice mode. I noticed that my distances shortened across all irons (~10 yards). I adjusted the elevation and it seemed to have worked, except for my driver still.

Has anyone else seen this? I am setting the red dot at the base of the tee. Am I doing anything wrong or does ST just not work with a driver?

[TorchRedRob]

Thanks for the great (as always) info, davray666. Makes perfect sense. I hadn't even thought about object distortion. I'd be surprised if they looked at calibration dynamically. Thanks again for the info. I've had my hands on various technology in my career, but optics and images are definitely not in my wheelhouse.

[SDL]

Very interesting conversation! I especially love the thought that goes into the comments from @davray666.

Now that I've had a chance to use my ST a bit more, I am getting pretty realistic distances with my short irons (compared to what I see on a real course), but I still don't understand the numbers I'm getting with the driver. I'm an old guy who has lost quite a bit of swing speed as I've gotten older, so I'm not expecting miracles from my drives, but the ST driver data don't quite add up for me.

I took a look at the ball speeds, launch angles, backspin, carry, and total distance I'm getting on the ST and then compared these numbers to several Trackman tables I found online. Working back from the on-course distances I see with my better drives (which go about 205-210 yards), the Trackman Driver Fitting Chart suggests that the following numbers will produce a 206-yard drive (assuming a positive attack angle): ball speed=111 mph, launch angle=15.3*, spin=1976 rpm, carry=156 y, and total distance=206 y. My ST numbers for several decent drives today averaged as follows: ball speed=109 mph, launch angle=15.8*, spin=2010 rpm, carry=156y, and total distance=180 y. All of the measured numbers from the ST (ball speed, launch, and spin) are quite similar to the Trackman chart for a 206-yard drive, and of the calculated numbers (carry and total distance) only the total distance differs significantly from the chart.

Is it just that ST uses an algorithm that calculates total distance a lot different than Trackman does?

[doublebogey]

Try changing ground condition to FIRM in the setting and you should get more roll and closer total distance - though 50 yds seems like quite a bit of roll?

[SDL]

The numbers I reported are using the "Firm" setting on the ST range since that matched the Trackman chart the closest.

[Sascha1818]

I have really never been looking at total distance. It doesn't help you. At different real courses it is different too. Even the same real course in the spring, in the late summer when it's dry, after a heavy rain, you will always have a different roll and therewith a different total distance. The only thing that doesn't change is your carry. Other then wind and elevation but you know that. So I actually never even pay attention to total. For me carry is the number.

[SDL]

I understand what you're saying, and I'm certainly more concerned about carry distance on a soft golf course. However, the launch conditions to optimize carry are different than those to optimize total distance. Using a companion Trackman fitting chart that optimizes carry for the same swing speed and positive attack angle would produce a ball speed of 108 mph, launch angle of 19.2, spin of 2720, carry of 164 yards, and total distance of 187 yards.

[SkyTrak_Seth]

Keep in mind that roll is totally subjective. 50 yards is a whole lot of roll! In testing, we found that the ball usually isn't rolling as far as one may think, but that's why we give options in the software to select between 3 different ground types. All launch monitors have different calculations as to what they think the roll out will be.

[mhage]

Can they just add an extra, extra firm so all the total distance guys will be happy???

[SDL]

It certainly appears that there are major differences in how each launch monitor considers the likely roll out for a particular ball flight. I'm just trying to self-calibrate my ST in relation to what I experience on the real golf courses I play.

Does the elevation adjustment for the ST range affect both carry and roll out? How much of a difference does each 5K foot change in elevation make - or is it more complicated than that?

[Sascha1818]

As well as sim software. Take your driver with Skytrak and WGT, E6demo and the skytrak range and each will show a different total. The carry will be pretty close but the total will be quiet a bit different.

[Thenatutal]

I also suspect my driver ball speed being low somewhere between 5-10mph, as a solid driver strike has equal or less then ball speed of a solid 3wood strike. After reading davrays explanation of the fish eye like distortion its got me thinking that if you were to elevate the skytrak unit to be level with the base of the teed up ball you might get a different ball speed reading for driver.

[Deuce]

t took mine to the driving range the other day to compare ST numbers to actual ball flight. After inputting the actual weather conditions and figuring out the alignment bias - my ST needs to be aligned about 1.5 deg to the left of my target line for a straight shot to show as straight - I found that the distances are consistently short throughout the set, but the gap gets more and more pronounced as you lengthen the club. The wedges were 5-10 yds short, irons 10-15 yds short, and woods up to 20 yds short. For example, I was carrying the ball past the 198 flag at my range, and it registered in the 180s several times. Not sure if it's worth returning or not, since it seems to be a common issue and the ball flight seemed to match fairly well, which is what I care about most. Does make it hard to play WGT, since you have to learn a whole new set of yardages.

[Deuce]

Good to know, and equally frustrating, that it's worse in WGT than ST; that helps explain a bit. I took my ST to the range again today and it was more accurate than the other day, though still seemed to indicate about 5-10 yds shorter than reality, but more consistently throughout the bag.

[mhage]

Did you verify the distances via laser? Was this with reduced flight range balls?

[Deuce]

I checked the distances against range flags that I've shot with my laser before, so I know exactly how far they are, and I used range balls, but many of them were just lost commercial golf balls. Not sure the golf ball would matter since it's actually measuring launch angle, ball speed, and spin, and thus the ST should match what you see from the actual ball, which was consistently short (using the ST range). Just not sure another unit would get me more accurate data. It seems like there's a wide swath of results - some are clearly exceptionally accurate and others not so much. My guess is I'm somewhere in the middle, but don't want to swap for another unit that's worse.