44 replies to this topic

[Blindkarma]

I recently bought a rangefinder with slope function. My first inclination was to spend $400, but as I checked the reviews, I found players saying straight distance accuracy is within a yard or two with cheaper brands. On an impulse, I bought a model under $250. As far as slope function, there were no comparisons between different brands. Surely each manufacturer must discuss their slope function formula, right? Nope! Only Bushnell even mentions it, stating they consulted renowned tour caddy Don Thom for his formula to adjust yardage readings for slope. I have no idea who that is, but realized their method was proprietary.

In another thread I asked if anyone knew the formula used in the device I just purchased. To my surprise, the manufacturer replied saying the height of a shot does not change the "metrics" because the distance and elevation change are constant. That reply is nonsense. Either he does not have a real answer or he was deflecting an important question.

Golf shots travel in an arc, not a straight line. The ball rises and then falls, so the height of the arc is critical to estimating carry distance to another elevation. The landing will depend on the height of the ball along the arc when it intersects the slope. Therefore, two players, A and B, with the same distance on a flat approach can have very different yardage playing to a slope if the height and arc differ. You could also apply it to the same individual using two different clubs that normally give him the same yardage but different trajectories.

I now question the usefulness of slope function from manufacturers who do not define their "corrected" or "adjusted" yardage. There must be differences for men and women, seniors and juniors, high-handicappers and low-handicappers. Any thoughts or real comparisons of devices?

Example of the issue below:

Edited by Blindkarma, 19 August 2017 - 07:43 PM.

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[Cwing]

Personally, I believe you are over thinking it. It is simply math and elevation change that's gives you the distance to a flag stick given the slope. The rest is simply what club the individual golfer will hit to get achieve that distance.

My buddy hits it way higher than I do but he is hitting his 160 yd club to the hoke just like I am. In this case, I'm hitting a 7 iron and he hits a 9 iron.

And yes, I understand that the height of the shot makes a difference on how the ball will react when impacting the ground.

Edited by Cwing, 19 August 2017 - 05:48 PM.

[Blindkarma]

If you think corrected yardage is simple math, then you know the pin moves very little on the x-axis from a particular point (example above shows 150 yds). It is the trajectory that becomes a big variable, and that is not simple math. The point of the drawing is to show you can't give one adjusted number to two players with different trajectories.

Edited by Blindkarma, 19 August 2017 - 07:39 PM.

[the bishop]

Then in answer to the OP's question I'm simply going to answer yes to fit his preconceived bias rather than argue.

[jj9000]

I agree with Cwing above.

Keep it simple.

160 yds = 160 yds...regardless of the over-analysis.

If you are 150 out...with an increase in slope that makes the hole play 160...you grab your 160 club.

There's really no need to add any additional variables...especially another player with a completely different swing.  

If you're a low ball hitter...you adjust for expected ballflight.

Grab your expected distance club and swing.

[Fade]

A rangefinder (which I take to be a laser-based instrument, not a GPS-based instrument) measures the straight-line distance from the golfer to the pin.  If you raise or lower the pin from 'level', the measured distance increases in both cases. But the downhill situation is not equal to the uphill situation, that is what the slope-function is supposed to correct for. You might need a club less in one case, a club more in the other. And trajectory would matter, as the OP demonstrated. And so might your stance, if that is uphill or downhill. So it is not simple math. My advice to the OP: You understand the complications, I would recommend you work off the straight-line distance measurement, switch off the slope function that you don't trust, and make the adjustments yourself.

[jll62]

Your diagrams are a little misleading because they're using nearly a 50 foot elevation change on a 150 yard shot. It's not often you run into holes like this, so you're exaggerating the difference between the shots in your diagrams to prove your point. My home club has a 160 yard par 3 with a 50 ft drop. Of all the courses I've ever played in my life, I can tell you that this hole is an outlier for slope. It's certainly not a hole upon which you should base your argument because you don't run across the situation very often. If you change the diagrams to show an elevation change that is closer to some sort of median slope change, the shots will finish closer together.

You're not incorrect in your overall premise. The slope adjustment is just a guideline based on certain factors. However, if someone hits anything close to an "average" golf shot as far as height goes, the slope adjustment is going to be close within a couple of yards. Even your exaggerated diagrams only show a 10 yard separation between the shots. Use a more realistic average slope change and that will be even tighter. Compare the distance between those shots to the average amateur's front-to-back dispersion of their shot pattern and I have no doubt that a slope rangefinder's yardage is more precise than the player's ability to consistently hit a shot that number.

I think you're splitting hairs on something that ultimately doesn't matter in practice. It's an approximation that's "good enough." It's up to you to deviate from the number depending upon your individual trajectory, etc.

[Shilgy]

So...op. Do you want a setting that selects what club you're hitting? Perhaps a setting that selects your apex height and descent angle? Do you think the professional caddie has an equation that does all of that? I don't care how renowned the caddie is he's still just using an educated guesstimate.

[jslane57]

I would not be surprised if the future of slope technology involves inputting user data such as club head speed and average, high, or low ball flight into user settings...

[matthewb]

I've retrofitted and modified a battlefield anti-missile defense system so that accurately calculates slope. Works great.

I can't believe that more of you haven't done the same.

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[HackerD]

Good question, OP and I agree it's not simple math.  Is it worth an extra $100+ for a slope adjustment that manufacturer won't disclose?

Its probably not worth getting too hung up on players with different trajectories requiring different adjustments.  To me, the nice thing about a laser with slope adjustment would be that it gives you an accurate read on elevation change.  Guesstimating elevation change is not easy.  The bad thing is, the device converts elevation change to a yardage adjustment based on an unknown formula.  

Rule of thumb I use is to add elevation increase to the total yardage (eg add 10 yds if target is 10 yds above me);  and subtract 1/3 of elevation decrease from the total yardage (eg subtract 3 yds if target is 10 yds below me).

[Stuart G.]

Blindkarma, on 19 August 2017 - 05:04 PM, said:

Golf shots travel in an arc, not a straight line.  The ball rises and then falls, so the height of the arc is critical to estimating carry distance to another elevation.

No, they don't travel on an that simple (or uniform) arc.  You can't use simple ballistics to calculate due to the lift generated from back spin.

The critical criteria in golf is the angle of decent - which can be very different for different players and different distances or even different shots  (a 150 yard 'knock down' with an extra club will be very different from a 150 yard regular full swing).   And the apex doesn't really dictate any particular angle of decent.   Which is why there is no one single calculation that can be used uniformly for everyone and every distance.

So is it a gimmick? - not quite.  The math used could be very valid and it's not necessarily any worse then any other model.  You just can't assume it will be valid for everyone or every shot equally.  Those that do use 'slope' will find they might need to make their own additional adjustments - depending on the level of accuracy desired and the level of distance and trajectory control you might have.

Edited by Stuart G., 20 August 2017 - 06:16 AM.

[cxx]

I play on hilly courses and have the bushnell . The slope adjustment is based on the trajectory of some "typical" golfer.  You can use the face value provided but if your trajectory is different, especially if it is lower, it will be off.  I know how much I need to adjust, depending on whether the shot is uphill or downhill and by how large the slope is.  If the slope is moderate, no adjustment is necessary.

[matthewb]

The question here is what is a difference that makes a difference? In other words, are the slope calculations accurate enough?

[Socrates]

I think Bushnell seems to have it right.  I hit a fairly high ball (I think normal for today's better player) and their adjusted yardages work for me.  Someone else who hits a low ball might think its off, I don't know.  There are too many other variables in play other than to provide you with a starting point to work with (wind, temperature, humidity, the lie you are hitting from, am I hitting it like crap today).

[mizirons]

The slope capable rangefinders have an inclinometer which calculates the angle of ascent or descent.   I used the PP 150 yard artwork examples with an assumed 20° angle on both the uphill and downhill targets.   The rangefinder uses the cosign of the angle to compute the relative distance.  If the pin is above the player, then the distance obtained by the laser will be the adjacent side of the triangle and the slope distance will be the hypotenuse.  When the pin is below the player then the hypotenuse will be the actual distance the rangefinder displays and the adjacent side will be the slope distance.  When the slope function  is turned off, the rangefinder gives distance to the target without regard for arc or other conditions, it's a straight line distance.  It's basically the same for uphill/downhill shots except with the slope function on the adjusted distance allows for the player to target angle of ascent/descent.   Not sure Pythagoras ever caddied, but he did the math work to make all this work.

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Edited by mizirons, 20 August 2017 - 01:12 PM.

[cxx]

mizirons, on 20 August 2017 - 12:27 PM, said:

The slope capable rangefinders have an inclinometer which calculates the angle of ascent or descent.   I used the PP 150 yard artwork examples with an assumed 20° angle on both the uphill and downhill targets.   The rangefinder uses the cosign of the angle to compute the relative distance.  If the pin is above the player, then the distance obtained by the laser will be the adjacent side of the triangle and the slope distance will be the hypotenuse.  When the pin is below the player then the hypotenuse will be the actual distance the rangefinder displays and the adjacent side will be the slope distance.  When the slope function  is turned off, the rangefinder gives distance to the target without regard for arc or other conditions, it's a straight line distance.  It's basically the same for uphill/downhill shots except with the slope function on the adjusted distance allows for the player to target angle of ascent/descent.   Not sure Pythagoras ever caddied, but he did the math work to make all this work.

Sorry that doesn't make sense. Here are the Bushnell readings from one of my  bigger uphill approach shots:
150/160 +4 155/166 +5 156/169 +5 167/180 +5 136/146 +5 119/129 +5
The plus numbers are the degree of slope. Cos of 5 degrees=.9962 .

I don't think I've ever seen anything close to a 20 degree slope for an approach shot. Just compare that with the launch angle of an iron. Makes no sense.

The Bushnell numbers are based on where a trajectory model would hit ground based on the slope to provide the "plays like" number.

[matthewb]

There isn't a problem just because the OP isn't aware of/doesn't understand the calculations for slope used by a device manufacturer.

What is the real world problem that's of concern here?

[Cwing]

Well ---- what do we do about wind, grain and soil type? Do we also need a moisture detector? What about sea level? They all matter to some degree.

All that stated, if my laser w/slope states the pin is 150 yds but slope adjustment is inducating it is 145 yds. I'm likely hitting 9 iron unless the wind is a factor.

Edited by Cwing, 20 August 2017 - 07:03 PM.

[jeggolfer68]

Add a thermometer to the unit and I may consider upgrading from my 20??? year old Bushnell. That's the model I use and compare yardages to my buddies latest and greatest. That old Bushnell and my 30??? year old Ping L wedge are workhorses.

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[apprenti23]

I love the slope function on my Bushnell There's been multiple times where I've said to myself "probably add ten here for the uphill" then I laser it and it says "add 3." The end result has me always much more accurate than my rudimentary calculations.

[Big Ben]

I think the rangefinders work better than my golf game so no complaints here...BB

[ray9898]

You are really over analyzing this.

[Duke of Hazards]

Leupold's newest models use a proprietary system (TGR-True Golf Range), wherein you enter variables
- one time (your carry distances with 3 key clubs (4i, 6i, 8i))
- altitude
- temperature

The altitude adjustment is likely set one time, unless you're travelling.  The temp adjustment is pretty easy, takes a few seconds at the beginning of your round.  I never really have to mess with it that much since I live in a temperate region.

Obviously, there are other variables (wind, an individual's high/low trajectory, etc), humidity, but all that said, the device will give you a fairly good approximation of the distance adjustment based on those factors.  

Where I play in So. California, I often have pretty big elevation differences to the holes (elevated tee boxes, or elevated greens), so the slope adjustment is quite useful.  I'm guessing less so in other regions, or on flat courses.


I have toyed around with the device and it does throw back much different adjusted distances if you enter club averages for a bomber vs. a short knocker (in initial setup), so there is some computing going on inside.

[benzenbe]

^^+1.  Was gonna say my Leupold GX-2i3 had me enter in carry distance, presuming it's because it factors in ball flight for those clubs and gives a more "proper" slope adjusted yardage.  In addition, when using True Golf Range (slope) it will display: (1) the degree of slope; (2) the slope adjusted distance; and (3) the actual distance.

https://www.youtube....h?v=u67eJm2iccE

[Krt22]

Very interesting question. I agree that the calculations wont be as accurate for a high ball hitter vs a low ball hitter.

Would be interesting if they if they really just use a straight forward inclination or if they have an equation built in that adjusts the approximate angle of decent (for some avg golfer) by distance (angle of decent will increase as the distances get shorter and shorter). Either way I'm guessing very few golfers are truely good enough for it to make a difference. They also get screwy on extreme holes (ie very downhill ), because in some of those cases the ball is coming in damn near vertical.

[Hondabuff]

Go buy a Bushnell Z6. Shoot the pin, buzz, buzz, 140 yards. Pull club that goes 140 yards. If its uphill swing harder, down hill swing easier. We are not launching Tomahawk missiles through bedroom windows here!  I found the slope feature annoying on my V4 and returned it.

Edited by Hondabuff, 24 August 2017 - 07:44 AM.

[North Butte]

I briefly used a Tour V3 with slope that I picked up inexpensively off BST. What I found was that none of the shots on my home course that I'd always wondered "how much uphill (or downhill) is that?" were enough uphill to make more than 2-3 yards difference. Sure, there are a couple of seriously uphill ones that are like +8 yards but those are obvious to the naked eye. I'd take an extra club anyway.

So to be blunt, I found the slope feature completely useless and redundant. I will say if someone played a much hillier course than where I play (gently rolling, ideal golf terrain) or especially if they regularly played unfamiliar, hilly courses it might be helpful. But I'm not worried to about a +2 or -1 yard slope adjustment and the larger slopes are easily assessed by looking at them.

[cxx]

If you play the same course all the time or play in flatlands like Florida or Texas, then the slope function doesn't add much.  It does help on hilly terrain.  Most people don't judge the effect of up hill or down hill shots well, unless they've played the hole many times.  If you play by the numbers, the slope function helps a lot.  Why else would they be illegal?

[Duke of Hazards]

I guess it boils down to where you live.  My home course has 2 elevated tee boxes on the front 9 alone (one is 150 feet drop to fairway, the other is 100).   These are extreme examples, but in the case of the first one, the yardage (without slope adjustment) would suggest 3w or driver.  I usually hit a 5 iron due to the drop.  If you're in a flat area where there's no significant elevation changes, then I can see it being annoying.

Edited by Duke of Hazards, 24 August 2017 - 03:23 PM.

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