What is the correct +/- for up and down hill approaches?

[sandsaver01]

I have just spent a little time on my designer-built practice range to come up with a small data set about the "distance v elevation" issue.

The experimental design was as follows: Hitting from flat fairway to flat green at various elevations above the golfer, <1 mph wind, using only P/P 100% swings and two replications. I only tested LW through 5I, because that is the main clubs you depend on to get close to the pin.

The data gave the graph below:


This is Carry distance only, I did not measure roll-out as that depends so much on slope.

I ran the numbers through an equation generating program, and as one could imagine from the nearly staight lines in the graph this gave a linear relationship; D = D0 - .318 X (for LW, more later)
Where D is distance, D0 is distance at zero elevation change, and X is elevation change in feet.

You can see that for this data set the 3:1 ratio is a pretty good estimate (that would give .333 X).

This breaks down a bit however when you look at other clubs longer than LW:

CLUB	COEFFICIENT X
LW	.318
SW	.314
GW	.324
PW	.326
9I	.326
8I	.347
7I 5I	.385 .412

So the bottom line for this small experiment is that the 3:1 or 1/3 rule holds up pretty well from LW to 9I, but starts to break down some as you get to longer clubs.

When I get a little time I will probably do negative elevation, because I am not sure that will give the same results.

[cephyn]

One key thing to realize is the 1/3 rule doesn't hold for pitch shots, only for full shots. And wind affects different length clubs differently, as well as pitch shots.

[sandsaver01]

Dec 26, 2019 20:47:17 GMT -5 cephyn said:

One key thing to realize is the 1/3 rule doesn't hold for pitch shots, only for full shots. And wind affects different length clubs differently, as well as pitch shots.

Both those things are true, Kevin. I am not taking wind into account at all for this study, and MOST of the time pitch shots are done with elevation changes smaller than I accounted for here, like 20 feet or so.

[sandsaver01]

Dec 26, 2019 15:05:00 GMT -5 sandsaver01 said:

I have just spent a little time on my designer-built practice range to come up with a small data set about the "distance v elevation" issue.

The experimental design was as follows: Hitting from flat fairway to flat green at various elevations above the golfer, <1 mph wind, using only P/P 100% swings and two replications. I only tested LW through 5I, because that is the main clubs you depend on to get close to the pin.

The data gave the graph below:


This is Carry distance only, I did not measure roll-out as that depends so much on slope.

I ran the numbers through an equation generating program, and as one could imagine from the nearly staight lines in the graph this gave a linear relationship; D = D0 - .318 X (for LW, more later)
Where D is distance, D0 is distance at zero elevation change, and X is elevation change in feet.

You can see that for this data set the 3:1 ratio is a pretty good estimate (that would give .333 X).

This breaks down a bit however when you look at other clubs longer than LW:

CLUB	COEFFICIENT X
LW	.318
SW	.314
GW	.324
PW	.326
9I	.326
8I	.347
7I 5I	.385 .412

So the bottom line for this small experiment is that the 3:1 or 1/3 rule holds up pretty well from LW to 9I, but starts to break down some as you get to longer clubs.

When I get a little time I will probably do negative elevation, because I am not sure that will give the same results.

I have now investigated the effect of negative elevation on club carry distance, and as I suspected there is a difference. Using the same equation as for uphill, the coefficient has changed from around 1/3 to closer to 1/4, and in a much tighter range as shown in the table below:

LW	.243
SW	.246
GW	.242
PW	.254
9I	.248
8I	.254
7I	.247
5I	.252

So I think one would be safe in using the 1/4 ( add 2.5 yards for every 10 feet of negative elevation change) as a general guideline. As always, the roll-out is highly dependent on firmness and up- or down-slope where the ball lands.