# Is slope function a gimmick for some rangefinders?

Blindkarma
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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:

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:

Post edited by Unknown User on Aug 19, 2017

## Comments

8,076✭✭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.

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2,650ClubWRXKeep 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.

1,167✭✭2,065ClubWRXYou'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.

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3,929✭✭1,825✭✭I can't believe that more of you haven't done the same.

3,175✭✭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).

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23,572✭✭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.

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113,136✭✭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.

1,825✭✭What is the real world problem that's of concern here?

8,076✭✭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.

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791✭✭129✭✭- 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.

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7,023✭✭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 **** near vertical.

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10,449✭✭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.

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