Collected Data on Arccos Accuracy

[ChetlovesMer]

Okay, so I’ve had this plan with the pro at my home course for a while now. I'm excited that I finally got a chance to sneak out and do this. We went out to the course with Trackman, Arrcos, our laser rangefinders and a pair of 6 foot long poles. Then hit tee shots while using trackman. Put the pole in the ground exactly where the tee was. We went to our respective balls. I used the laser rangefinder to get the distance from the pole, then stuck the second pole in the ground where my approach shot was struck.

Then I went to my ball and repeated the process. After each hole I recorded the data from the rangefinder distances and the trackman. Later I compared it to the Arccos data. We wanted to do this over 18 holes, but it was a pain in the @ss to do so. So, we only did 9 holes. The conditions were super wet and very overcast, on the verge of rain any second. Which may or may not have affected things, but it did keep the course pretty empty which worked to our advantage. 

By the way, I assume my Bushnell Range Finder is pretty good. So, I'm assuming that is actually distance. I'm also right handed and keep my cell phone in my left front pocket if that matters. 

 

My Data

Hole                                                 1            2            3            4            5            6              7            8            9

Rangefinder Distance                   243        222        N/A       267        251        N/A            251        255        239

Arccos Tee-shot                           242        224        N/A       266        249        N/A            249        254        237

Trackman Carry                           239        251        N/A       258        246        N/A            248        252        235

Trackman total distance              256        268        N/A       277        261        N/A             255        255        238

 

Hole                                                 1            2            3            4            5            6              7            8            9

Rangefinder Distance                   121        138        131        184        115        169           204        104        139

Arccos Approach shot                  121        138        130        183        114        169           202        104        140

Trackman Carry                           121        136        131        181        114        165           198        131        139

Trackman total distance               124        139        132        192        117        167           209        138        146

 

Some information on the data. My tee-shot on hole 2 hit a tree. So we think it confused the Trackman. I also punched out from under that same tree on hole 2. I used a 5 iron. I didn’t include that shot in any of the data.

On hole 8, my approach shot hit a tree. Once again, we think it confused the trackman. We assume the trackman follows the ball as long as it can and then once the ball hits the tree trackman loses it. So, it probably just calculates from there.

Both hole 4 and 7 are par 5’s. I didn’t include any of the data for the 3^rd shot on either hole. They were both short wedge shots. 19 yards and 47 yards respectively.

Some more things we noticed. The course was super wet, and the grass was long, both in the fairway and the rough. It has been raining like crazy out here in Ohio. Our drives got almost no roll. The trackman continuously gave us credit for way more roll than we actually got. What we did notice that was really cool was that the trackman was pretty close on drives in which I hit a fade. Look at holes 7, 8 and 9. Those were all fades. Trackman was close. On holes 1, 4 and 5, I hit draws off the tee. Trackman naturally assumed those would run out, but none of them did. It was way too wet and thick. Of course hole 2 hit a tree and well, we’ll never know.

 

Some other things I wanted to mention, just about Arccos. On hole 2 I hit only 1 putt, but Arccos showed 2… I’m not sure how that happened, It sometimes doesn’t record all my putts, but that’s the only time I remember it adding one. Not sure what happened there. Of course, it is easy to correct. On hole 8 Arccos had me down for 2 putts as well, but I actually hit 3. That sometimes happens, where Arccos doesn’t catch one of my putts, usually it’s a tap in where I forget to hold my putter still for a second before making the stroke. Again, easy to correct as you walk off the hole.

 

Okay, last observations I’d like to mention. I’ve been told that civilian GPS is not that accurate. We found it to be pretty darn close when it tracked shot distances. Where we think it was less accurate was when we measured distances on the course. We had a theory that shot to shot it is pretty accurate, like maybe it makes a mark on it's global positioning or what ever and then a new mark again and just gives the distance between the two... pretty accurate. But when measuring from where we are to a landmark (for example the center of the green) it seemed less so. Like maybe it knows where we are, but doesn't exactly know where the landmark is. We didn’t keep data on this, but it seemed like Arccos distances to the center, front, and back of the green was sometimes off by up to 3 yards or so. Maybe that was just our impressions, like I said we are not experts or anything. I’d love to hear more about what some of the rest of you think or have found.

Overall I will say I was pretty impressed with how close Arccos distances were in relation to what we measured with the range finder. It was literally better than I thought it would be. 

[iacas]

What was your goal here?

[ChetlovesMer]

Just now, iacas said:

What was your goal here?

I was very curious to see how accurate Arccos data is. I've had discussions where people have told me that it's not even close. I found it to be very close. Granted only 9 holes, but it was truly better than I thought it would be. I figured the averages would all work out to about right, but I guessed shot to shot would show more inaccuracies. 

If you're asking about why we included trackman. The pro wanted to use trackman too. He tells his clients that trackman gives accurate information and they sometimes argue with him about it. He was curious so was I.

I would have loved to have also used a GC Quad. But neither of us had access to one.

 

[billchao]

1 hour ago, ChetlovesMer said:

We assume the trackman follows the ball as long as it can and then once the ball hits the tree trackman loses it. So, it probably just calculates from there.

I'm pretty sure that's what it does. It's how it gives you ball data if you're hitting into a net.

1 hour ago, ChetlovesMer said:

Some more things we noticed. The course was super wet, and the grass was long, both in the fairway and the rough. It has been raining like crazy out here in Ohio. Our drives got almost no roll. The trackman continuously gave us credit for way more roll than we actually got. What we did notice that was really cool was that the trackman was pretty close on drives in which I hit a fade. Look at holes 7, 8 and 9. Those were all fades. Trackman was close. On holes 1, 4 and 5, I hit draws off the tee. Trackman naturally assumed those would run out, but none of them did. It was way too wet and thick. Of course hole 2 hit a tree and well, we’ll never know.

Total distance is calculated.

https://blog.trackmangolf.com/total-distance/

[ChetlovesMer]

12 minutes ago, billchao said:

Total distance is calculated.

https://blog.trackmangolf.com/total-distance/

Cool, thanks for the link. I learned something new today.

[Pretzel]

Being within 2-3 yards of the distances on all your shots doesn't surprise me too much. The accuracy of civilian GPS has a minimum of 7.8 meter range accuracy 95% of the time, but interestingly enough the specs have improved and now the average "User Range Error" is 2.3 feet 95% of the time. This doesn't mean that GPS devices are accurate to that size of a hoop around you, it's just the accuracy of the distance between you and the satellite. This roughly translates to an average accuracy (in mid-range user devices) of a 3 meter circle. High end devices can manage 1-2 meter accuracy in good conditions, but they're quite expensive.

The primary reason military GPS is more accurate is access to the P(Y) code (old version) or M-code (new version) that is encrypted and transmitted alongside the freely available civilian data. It can include error correction and forward error correction, and it significantly helps with ionospheric correction to increase accuracy. The new M-code will also be transmitted (once new satellites are launched) with directional antennas that can increase signal strength in specific areas as necessary. I've had long conversations with a senior engineer in charge of a GPS replacement celestial navigation system (for use in military vehicles if GPS systems are down) and have been told that the accuracy of the military GPS is usually within 5 centimeters of the actual location and that their goal was to match or beat that accuracy.

Interestingly enough researchers as early as in 2016 have found techniques that can make even civilian GPS accurate to within 1 inch of your actual location by combining data from GPS satellites and sensors onboard the device that is being located. That said, since 2000 the gap between civilian and military GPS has been shrinking since the US stopped randomly offsetting the GPS data (initially by up to 400 meters, since it was intended for use in ocean navigation) that was transmitted by satellites. Civilian GPS still doesn't have access to encrypted data that the military uses, but interestingly enough clever systems used to be able to use the old P(Y) signal to help with error correction even if they couldn't read the data in the signal itself.

Basically, the gist of it is that GPS is going to be more accurate than you pacing it off, but only marginally less accurate than most standard laser rangefinders.

[ChetlovesMer]

22 minutes ago, Pretzel said:

Being within 2-3 yards of the distances on all your shots doesn't surprise me too much. The accuracy of civilian GPS has a minimum of 7.8 meter range accuracy 95% of the time, but interestingly enough the specs have improved and now the average "User Range Error" is 2.3 feet 95% of the time. This doesn't mean that GPS devices are accurate to that size of a hoop around you, it's just the accuracy of the distance between you and the satellite. This roughly translates to an average accuracy (in mid-range user devices) of a 3 meter circle. High end devices can manage 1-2 meter accuracy in good conditions, but they're quite expensive.

The primary reason military GPS is more accurate is access to the P(Y) code (old version) or M-code (new version) that is encrypted and transmitted alongside the freely available civilian data. It can include error correction and forward error correction, and it significantly helps with ionospheric correction to increase accuracy. The new M-code will also be transmitted (once new satellites are launched) with directional antennas that can increase signal strength in specific areas as necessary. I've had long conversations with a senior engineer in charge of a GPS replacement celestial navigation system (for use in military vehicles if GPS systems are down) and have been told that the accuracy of the military GPS is usually within 5 centimeters of the actual location and that their goal was to match or beat that accuracy.

Interestingly enough researchers as early as in 2016 have found techniques that can make even civilian GPS accurate to within 1 inch of your actual location by combining data from GPS satellites and sensors onboard the device that is being located. That said, since 2000 the gap between civilian and military GPS has been shrinking since the US stopped randomly offsetting the GPS data (initially by up to 400 meters, since it was intended for use in ocean navigation) that was transmitted by satellites. Civilian GPS still doesn't have access to encrypted data that the military uses, but interestingly enough clever systems used to be able to use the old P(Y) signal to help with error correction even if they couldn't read the data in the signal itself.

Basically, the gist of it is that GPS is going to be more accurate than you pacing it off, but only marginally less accurate than most standard laser rangefinders.

Uh... I was told there would be no math...

[Pretzel]

2 hours ago, ChetlovesMer said:

Uh... I was told there would be no math...

Don't worry, I skipped the complicated bits for you! 😁

GPS is a cool subject, and the improvements for it have been pretty significant since the 2000's when the intentional offsets were removed.

[lastings]

cool.   now if I could learn to just hit a ball 2-3 yards from where I'm aiming, I'll be all set.  

[ChetlovesMer]

Just curious, have any of the other Arccos users (or Game Golf for that matter) out there done any research to test the accuracy or precision? It doesn't seem like there's a lot of actual data out there on this. If somebody has a link to something I'd be interested. 

[iacas]

6 minutes ago, ChetlovesMer said:

Just curious, have any of the other Arccos users (or Game Golf for that matter) out there done any research to test the accuracy or precision? It doesn't seem like there's a lot of actual data out there on this. If somebody has a link to something I'd be interested. 

I don’t see the point. I measure with a laser when playing and look at the results when I edit/review my round.

The numbers are what I’d expect.

[lastings]

15 minutes ago, iacas said:

I don’t see the point. I measure with a laser when playing and look at the results when I edit/review my round.

The numbers are what I’d expect.

not everyone uses a laser, and I guess the point would be that its nice to know how accurate the GPS actually is..